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  1. #1
    RC Turnbuckle Jr.
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    E-Revo FAQ & Tutorials

    CONTENTS:

    1. Chassis
    2. Transmission
    3. Drive shafts
    4. Bulkheads
    5. Shock towers
    6. Differentials
    7. Knuckles & suspension
    8. Skid plates
    9. Steering mechanism
    10. Wheels and tires
    11. EVX, EVX2 & MMM speed controller
    12. Nimh Batteries
    13. Titan & NeuCastle motors
    14. V-twin concept
    15. BL system upgrades
    16. Lipo & A123 batteries
    17. Chargers & balancers

    1. Chassis

    E-Revo & BL E-Revo
    Stock E-revo uses a monocoque type molded chassis with integrated battery compartments, greatly increasing the overall strength and rigidity of the truck. The downside is that you are rather limited on the type and size of batteries that you can use. 7 cell side by side nimh packs fit fine, but you are restricted to 8000mah 2s, or 5000mah 3s lipo packs. In theory this sounds fine, but in reality if you are using a powerful BL motor and esc setup, you are forced into buying pricey high spec packs made from Enerland cells; you may not get such good results from over spec’d cheap Chinese cells that perform well with stock electronics or lower powered BL systems. Although the chassis is made from plastic so far there it has proven itself to be a quite robust design, thanks largely to the clever and rather beautiful skid plate that runs the full length of the chassis’ underside, tying it together with the bulks and skids. One potential weak area that has become apparent is the rear portion of the chassis that links to the bulkheads is prone to excessive flex if you jump the truck or bash hard. There is a fairly simple fix for this though & requires minimal modification; a spare suspension tie-rod can be bolted to the base of the wing mount & then bolted to a small plate attached over the rear shock-tower, thus stiffening up the chassis greatly. Up-top, the esc and radio are mounted on the battery compartments, a clever idea since there is plenty of room this way, but locating the esc in the correct place is critical as the battery leads may not reach if they are a little short. The BL Erevo has its MMM esc mounted in the best place to ensure the battery wires will reach- there are dual input connectors for running a pair of lipos in series ( no extra harness required ordinarily ). It is also worth noting that the holes in the battery compartments for the battery wires to exit may not line up perfectly with the battery leads, where they exit the lipo/ nimh packs, so a little light modification may be required.

    Conversion
    There are two options, the 2.5 and 3.3 spec revo chassis. The 3.3 would be favourable since the longer wheelbase makes for better handling, and more room to mount the electronics etc. As for the specific conversion route, there are a handul of nice options:

    • Emaxx tranny conversion (old or new model)
    • Stock revo tranny with RC-Monster motor mount
    • Stock revo tranny with TeknoRC (ImPaktRC) electri-clutch or standard pinion and motor mount

    When using the emaxx tranny, you essentially just have to dremel the chassis a little to mount it, then come up with some battery trays depending on what you plan to run exactly. When using the stock transmission & rcm mount, you have two options:

    • Lock the tranny into 2nd gear, and use motor braking via the esc
    • Keep the 2spd, and use mechanical brakes

    If you choose option 2, which also applies to the TeknoRC option, you are also able to use a forwards only esc, such as a heli or boat model; you may also need to use the ‘PiStix’ item, which converts the radio signal into something the esc can understand, as aero escs use different signal patterns to car/truck escs. In addition, when using either of these options, you are fairly limited to your battery mounting options, with only one side of the chassis free.

    2. Transmission

    E-Revo & BL E-Revo
    The stock transmission has been greatly strengthened with the use of steel idler gears that are wider and stronger. The transmission comes locked into 2nd gear as standard, handy for those who use BL power in their trucks. An optional 2speed kit is available that reinstates 1st gear, with a choice of close and wide ratio gear sets; top speed remains unaffected. The new transmission features a Revo spec slipper assembly that can be used with spurs ranging from 54tooth (jato 3.3) upto 68tooth that comes as standard in 32p (MOD 0.8). MOD1 spurs from the Revo can also be used provided a MOD1 pinion is also used- these are available from RC-Monster and RobinsonRacing as well as a few other places. The new transmission has been designed to allow the use of twin motors, as in the stock setup, or a single motor that can be mounted centrally- either with the stock motor mount or an option single motor mount and gear cover. The BL Erevo has the single motor mount & cover as standard & comes supplied with the CastleCreations NeuCastle 2200kv motor + 18/65 gearing. It is also worth noting that finned can motors (such as Neus) or larger diameter motors (Neus again, and KB45s) may be limited in their gearing range as the larger diameter cans may hit the transmission case before the pinion and spurs mesh correctly. With the lowered central motor mount there is the option to mount a large motor with a 30mm mounting pattern, such as the KB45 or larger brushed motors such as those sold by kershawdesigns and banebots etc.

    Conversion
    The stock emaxx 3906 transmission is a 2 speed unit that is shifted via a servo; when used in a revo conversion, keeping the 2sp option is difficult, but not impossible. There are a few weak points to the design however, mainly concerning the slipper mechanism and idler gears. The stock slipper uses small pegs inserted into the spur gear and a spring loaded pressure plate to control torque delivery; the problem is too much slippage causes the slipper pegs to melt, and the spur will just spin and spin, without sending any power to the wheels, or the slipper plate will overheat causing the spur gear to melt in the center. Simple solution is to tighten the slipper fully, though this does add more stress to the driveline resulting in broken driveshafts and diffs. Best solution is to skip the out-dated 3906 transmission & opt for the much better 3905 spec transmission. This is slightly narrower than the 3906 version so will require a small mounting adapter along one side in order to fix it to the chassis, relatively simple with some basic hand tools & some 3mm thick aluminium. GorillaMaxx also sell a single speed conversion kit that removes 1st gear and half the transmission case, an ideal way to save weight and eliminate the shifting mechanism, though that still leaves you with the weak plastic idler gear and slipper mechanism- the best option to fix this is to modify the transmission to use the 3905 spec slipper assembly (CLICK HERE). Then, add an Unlimited Engineering ( UE ) or Rc-Monster steel idler. The Erevo spec tranny has all the same features as the Emaxx 3905 tranny. The stock nitro revo trannies are essentially fine, though there are various retailers offering upgraded gear sets and such. Locking the nitro tranny into 2nd gear is a painless enough job, and requires minimal work- see the links thread for a 'How-to' guide.

    3. Driveshafts

    E-revo, BL E-Revo & Conversions
    Very few people have reported issues with the new style of drive shafts, though they are still possible to twist and snap, especially in cold weather. Traxxas CVDs are a nice upgrade, though they themselves are not 100% bullet proof as the dogbone pin can snap under BL power. Being less aggressive on the brakes and throttle can reduce the amount of stress on these parts.

    4. Bulkheads

    In all my years of studying revos and revo conversions, I have only ever seen one or two broken bulkheads, and the new E-revo uses an improved design for even greater strength, so no worries there. The usual source of problems comes from the possibility if broken rocker posts, that rarely sometimes snap of, leaving a stump poking out of the bulk- cheap to replace.

    5. Shocktowers

    E-revo, BL E-Revo & Conversions
    Since they only have to support the shell, they are much more durable and I’ve never seen a broken one, so again, no worries there. I would be inclined to say stick with stock or plastic models though, as aluminium versions will only transfer stress to more critical areas in a crash or flip.

    6. Differentials

    E-revo, BL E-Revo and Conversions
    Traxxas improved the design somewhat with a Revo type sealed diff and additional spider gear support, but the cup and case are still plastic. Unfortunately there are no aftermarket cases that will fit at present, though FLM sell a metal cup that will remove the flex of the stock setup. The only real option for bullet proof E-revo or revo diffs at present are the RC-Monster V2 hybrid diffs, that use 1/8scale buggy or truggy diffs, and fit in the stock bulkheads. You will also require dogbone cups that fit an 8mm output shaft, or the RCM adaptor that allows you to use the stock center shafts instead of dogbones. Another more complicated upgrade option is to modify ( dremel... ) the inside of the bulkheads to accept LOSI LST-2 or Muggy diffs- see the 'Truck Links' page for a link to some guides & examples.
    Keeping the Mods busy is my specialty...

  2. #2
    RC Turnbuckle Jr.
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    7. Knuckles & suspension

    E-revo, BL E-Revo & Conversions
    Again, the stock design is pretty solid, though the pillow balls are known to pop out sometimes due to the soft plastic used in the knuckles- RPM knuckles are even softer it is worth noting, but they tend not to break so easily. Aluminium knuckles are a great upgrade, though this does remove a weak link from the truck, and will shift potential damage to other areas in a crash or cartwheel etc. RPMs rear suspension upgrade is good for people who don’t like messing with toe angles, as it locks the wheels to 1.5 degrees of toe-in, good for racing and all-round use generally.

    The stock suspension arms are pretty sound, but RPM offer some nice upgrade items that are almost unbreakable. Ofcourse, there are also numerous aluminium options too along with Ti arms, it is a matter of personal taste as to which route you take, though RPM arms are very robust and ideal for people who are hard on their trucks. Set-back arms are a nice option also to increase the wheelbase, and reduce wheelies. The stock E-revo comes with fairly soft suspension setup as standard; this can be improved by fitting stiffer springs- refer to the manual for specific details (yeah I know, but there you go ) on setup guides. For off-roading action, use of the long travel rockers is a good idea, as it allows for more suspension travel, with greater ground clearance and smoother handling over the rough stuff.

    8. Skid plates

    E-revo, BL E-Revo & Conversions
    The stock items are fairly sound, though there are also numerous aftermarket options for the nitro models, such as one piece ‘armour’ that covers the whole underside. Ti is always my favourite material as it is strong, light, and flexible.

    9. Steering mechanism

    E-Revo, BL E-Revo & Conversions
    The stock setup is fine essentially, the only real weak point being the weak gears in the servos, though this hasn’t been so much of an issue as compared to the 3905 servos that stripped due to a poor initial servo saver design, thankfully fixed now by traxxas. When looking at a new servo, try to find something with over 200oz/in of torque, be it digital or analogue. Metal gears will be more robust than nylon or Karbonite. There are numerous metal aftermarket models available, some of which aloe the use of dual, or a single high-torque servo. The BL E-Revo comes with optional steering stops that allow greater side to side movement for the steering; why Traxxas doesnt just include this on the truck as-standard to begin with makes little sense, but never mind..

    10. Wheels and tires

    E-Revo, BL E-Revo & Conversions
    The standard brushed setup uses a 14mm hex to mount the wheels onto the stubaxles. Aftermarket hexes and adaptors allow you to use anything between 12 and 23mm- 17mm and 23mm being the most common generally. The advantage here is that a larger hex diameter is less prone to stripping out inside the wheel- you will obviously require a wheel (or rim) that uses the same size hex as the one on the truck. For general use the stock chevron design tire is fine, though there are much better choices for onroad and offroad use, depending on the specific surface (hard dirt, loose soil, grass, tarmac etc). Proline, GRP, Maximizer are but a few of the aftermarket companies offering wheels, tires and hexes. Under BL power and high rpms many tires tend to ‘balloon’ in diameter, which can cuase them to tear or fly apart, or at the very least cause loss of control. One solution is to use tire foams, and another is to belt the inside of the tire with thick duct tape (turn the tire inside out and run a couple of strips of tape around the tire, being careful not to overlap the edges which would cause imbalance). Traxxas themselves have introduced a 17mm hex and rims with the Revo Platinum, and this offers users yet another upgrade route. The BL E-Revo comes with 17mm traxxas hex adapters and matching rims- these are the same 'toothed' hexes as used on the BL E-maxx, taping the insides of the tires to reduce ballooning and high-speed blowouts is advised.

    11. EVX, EVX2 & MMM Speed controller

    E-revo
    Again, despite traxxas’s boasting the blue EVX2 is water proof, it is ill advised to test this too far, as traxxas will charge for repair of any moisture damaged escs. It suffers in general to a lack of voltage handling ability as freshly charged 6 and 7 cell packs can sometimes trip some form of over-voltage protection, though this isn’t the case with all EVX2s which is somewhat baffling. It is also recommended that you do not use the on/off switch at the end of a run, but to instead simply unplug the batteries from the esc. Any warranty issues should be dealt with by contacting the Traxxas customer service department.

    BL E-Revo
    The BL E-Revo comes complete with the brilliant CastleCreations MambaMonster ( MMM ) brushless esc and motor system. The esc is rated for 6s lipo or 18 nimh cells, the motor is the NeuCastle 1515 1y 2200kv model, based on the popular Neu of the same specification. The BL E-Revo comes with factory gearing of 18/65 which is good for about 35mph with 14 nimh cells or 4s lipo. With the optional 18/54 gearing 40mph is easily possible, but only with good quality lipos; nimhs will not provide sufficient current ( amps ) for the esc & motor, and esc damage may occur. This is due to something known as 'ripple current', whereby the voltage from the batteries fluctuates rapidly and drops as the current output increases beyond what it can provide due to high Internal Resistance ( IR ). Lithium batteries have much lower IR levels and so do not overheat or droop their voltage output under such strain ( provided they are of a suitable specification ). With 6s lipo & the correct gearing ( 24/54 ) it is possible to achieve a maximum speed of around 65-70mph, though aerodynamics & tyre choice become critical issues at this speed; strictly for on-road use only. It is very important when choosing lipos to select items with a good specification & that will provide sufficient current for the MMM to operate properly. The esc requires lipos capable of producing at least 120amps continuously, though the more overhead you have, the longer the batteries will live for and the longer your runtime will be ( as an indirect effect the voltage will not drop below the Low Voltage Cutoff ( LVC ) until nearer to the end of the discharge ). To determine how much current your lipos will produce, simply multiply the C rating by the mah capacity & devide by 1000, for example: 20c x 5000mah / 1000 = 100amps, or 40c x 5000mah / 1000 = 200amps. For best results the lipos should be of identical specifications & age/ discharges, though it is perfectly fine to use two different voltage/ cell counts in series, such as a 3s & 2s lipo to achieve 5s lipo ( I like 5s lipo as it is the perfect mix of power and speed when geared for about 40mph ). The MMM esc has numerous programming options & settings that are accessible via the 'CastleLink' programmer. This unit plugs into the rx lead from the esc & connects to a PC to allow changes to be made to various settings such as punch & torque control, LVC settings, timing and start power, brake strength and also throttle curves etc etc; the 3908 does not come with this unit so it is an optional extra costing approximately $25; well worth purchasing. Please see new Castlelink page on my website for indepth info on how to use this device and the best settings.

    12. Nimh batteries

    E-Revo & Conversions
    The best way to get good performance from any E-revo is to use good batteries, as these ultimately determine your runtime and the amount of ‘punch’ & top speed your truck will have. When choosing packs, consider the amount of capacity they have in mah (Milli-amp Hours), the cell count/voltage, and the discharge rating if available. Higher mah will mean longer runtime, higher voltage will mean greater top speed, and a higher discharge rate will mean more punch along with more consistent top speed and acceleration. There are a great many brands out there, so choosing the best for your needs is somewhat tricky sometimes. In general, try to avoid cheap 6 cell shotgun or stick packs form Ebay, as these are assembled using thin tin strips to join the cells. Good quality brands are IB, EP and ENER-G, though there are many others. It is important not to overheat any battery, or to miss-treat it, as this can lead to ruptured cells or blown end-caps. Be sure to observe the correct polarity when building packs from scratch or adding cells to packs. 7cell side by side packs are best to achieve a good fit in the battery compartments, and for maximum speed.

    BL E-Revo
    CastleCreations themselves do not recommend using nimh batteries with the MMM esc as they cannot provide adequate current to meet the demands of the motor, yet at present Traxxas supply the BL E-Revo with a pair of 3300mah packs; go figure. These or better quality nimh packs will be sufficient for about 30mph on the stock 18/65 gearing- do not attempt to excede this figure as esc damage may occur; you have been warned.
    Keeping the Mods busy is my specialty...

  3. #3
    RC Turnbuckle Jr.
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    13. Titan & NeuCastle motors

    E-Revo
    Older titans seemed to be more resilient to 16.8v use compared to newer titans, though this could just be a matter of perception; more internet users = more reports of failures. At any rate, it is important to use 19-23 turn motors with the E-revo and EVX & EVX2 escs on 14.4 to 16.8v. Using 12 turn motors on Emaxx voltages will result in burnt out motors and escs. There are various upgrades to look at when choosing new brushed motors for the Emaxx, from the $3.50 drill motors all the way up to expensive 19turn racing motors that need rebuilding after every run- the cheaper options tend to be more hardy and last a lot longer, and still give impressive results. KershawDesigns offers more options in the shape of larger motors, such as the 650, 700 HO and 970 sized motors, some requiring a custom motor mount and pinions in order to fit on the E-revo transmission. Performance gains vary, but weight gain definitely increases with the larger motors, and run time drops.

    BL E-Revo
    The BL E-Revo uses the brilliant NeuCastle 1515 1y 2200kv motor, based on the original Neu design of the same specification. The motors are made under license to the same spec as the original Neus, but there are various subtle differences that make them much better suited to use in ground based vehicles. The endbells are screwed in place & sealed to prevent the ingress of dirt and dust & to increase durability. The wires are no longer extensions of the windings from inside the motor, instead they are very flexible 10guage wires that can be shortened as required. The motor shaft comes with a large flat spot as standard to make attaching a pinion much easier ( though a drop of blue threadloc is always recommended ), and there is a shield inside the front endbell to prevent mounting screws that are too long from damaging the coating on the windings; screws no longer than 8-10mm are suggested, trim as required. To protect the motor wires, it is best to install the motor with the wires facing either downwards or off to one side, but not directly upwards- in the event you roll or flip the truck without it's shell on you would otherwise damage or strip the insulation from the soft wires. If you are looking for more runtime and cooler temps, it is a good idea to look at the NeuCastle 1518 1y 1800kv motor. This is slightly longer and a lower kv rating compared to the stock 1515 motor, meaning that when used with the same voltage and gearing it will result in a lower wheel speed and lower temperatures due to less current draw. When paired with 6s lipo and suitable gearing the 1518 motor makes for a very potent setup with outstanding torque, lower running temps & longer runtimes- a great motor for speeds in the 40-50mph region, and also for heavier trucks with a lot of after-market aluminium parts and/ or large & heavy tires. You will need to dremel a small amount of material from the rear shock-tower mount to allow room for the longer motor, but it is very minimal & wont harm the truck's durability.

    14. V-twin concept

    It’s actually remarkably simple really. All that is required is a pair of Traxxas VXL systems, a servo Y-harness, and 2 ounces of common sense & initiative. Bolt both motors to the transmission, and connect the escs to the receiver (rx) throttle channel via the servo Y-harness. Then, programme the two escs at the same time to your radio, and that’s it. The only difference here compared to the E-maxx V-twin is that one motor is reversed; simply switch any two of the wires from the esc to the motor around (outer two ideally, leaving the centre wire alone). You will need to use the same size pinion on both motors, and ensure the mesh is set correctly- use a piece of paper between the spur and pinion as you mesh them together, to prevent them binding too tightly. To get the best performance from a V-twin it is vital to use good batteries, this generally means a pair of 3cell (3s) lipos. To ensure even discharging on each system, it is a nice idea to use a parallel harness. It essentially is a pair of leads with male plugs at one end, and female at the other, with a wire linking the negative wire on each lead, and the positive leads in the same way. This ensures that the batteries discharge at the same rate, preventing the LVC from kicking in on either system before the other- see below:

    SYSTEM WIRING

    PARALLEL HARNESS

    Topspeed is around 55-60mph with good lipos and careful gearing, though it is important to keep a close eye on motor, esc and battery temps.

    15. BL system upgrades

    E-Revo & Conversions
    The faithful old HvMaxx systems are a nice intermediate upgrade, working well on both 12-14cells and a pair of 2s lipos with an LVC device. The Hv6.5 motor is seen as the best version, giving the best temps and good speeds of around 35-38mph. The Hv4.5 motor will give higher speeds of around 43mph, but at the expense of higher motor and esc temps- be careful not to thermal the esc as it can become permanently damaged. Next step up is to either buy an MMM esc & 2200kv motor kit, or build a custom system basically, using either a MambaMaxPro (MMPro) esc or the MMM esc and a Feigao-type L or XL can motor. The best motors to use would be either the 9 or 10L to get good speed, and the 8XL or 9XL for good speed and more torque. Using motors with fewer turns/higher KV rating (rpms per volt) will result in higher temps and potential damage to the motor, esc and batteries. 100-180f is generally seen as the safe zone for motors and escs, with 135f or below being optimum. There is an old rule of thumb regarding temps which many will find handy no-doubt:

    Hot motor + cool esc = under geared.
    Cool motor + hot esc = over geared.

    As a general rule this is fine, though it is possible to get different results depending on the esc and motors used- some motors run hot regardless, and some escs are less capable than others to deal with high current draw. It is important to choose a suitable sized and KV motor for MT use- 36-39mm diameter, and 60-80mm in length is a good guide. The KV rating will depend on your voltage, but as a general rule again:

    2000-2700kv = 4s lipo/ 12-14 cells
    1800-2200kv = 5s lipo/ 14-16 cells
    1500-2000kv = 6s lipo/16-18 cells

    If you are planning on using more than 6s lipo, chances are you don’t need to be reading this FAQ…
    Beyond that there are higher end escs such as the Quark 125b, MambaMonster (MMM), Kontronic Jazz, Schulze, Hacker mastercar, MGM, and so on. Ideally, you want an esc that can handle upto 6s lipo or more, and is rated for atleast 120amps ideally.
    High end motors tend to take the shape of Neu 1515 or larger models, Lehner 1940 and larger models, Hacker C50maxx and Feigao XL models, and the Castle-Neu MMM motors, along with the Medusa 60-80mm models, and Megamotor 22/45 series. There are numerous other good quality motors these days that are suspiciously similar to the Neu & NeuCastle motors, such as the offerings from Hobbywing & Leopard motors- good quality motors, but using lesser magnets than the higher quality motors; exploded rotors & higher running temps are likely if you arent careful with the gearing & kv/ size choice for your application. The Plettenberg BigMaxximum used to be concidered the very best of the best, but these days this 4 pole German monster is very overpriced & has a kv rating much too high for use with anything other than 4s lipo- does not make for a very efficient setup at all.
    The stock radio system does a reasonable job with the stock setup, but BL systems tend to create a lot of RF (radio frequency) electrical noise, and Am radios do not react well, with glitching and loss of range & control a common problem. Best solution is to upgrade to an FM radio at the least, or a digital radio is even better, budget permitting.

    16. Lipo and A123 batteries

    Lipo = lithium polymer. They have a nominal (resting) voltage of 3.7v per cell, and a fully charged voltage of 4.2, but unlike Nimh cells, you can actually select the fully charged voltage provided you have a suitable charger; this is handy for escs that don’t like peaked voltages sometimes (MambaMaxx and Quark 125b for example). When charging, and discharging (running them in a vehicle), the individual cells in a pack can become out of balance. This means in a 2s pack for example (s = cells in series), one cell can read slightly higher or lower than the other, and over time this difference can become large enough to mean that one cell becomes over-discharged during use; it is important not to discharge them below 2.8v per cell, but 3.2v is a safer level. This is where the LVC device comes into play, as it cuts the throttle, or reduces power when the cells have drained down to whatever the cut-off voltage is set to. Some LVCs have adjustable voltage settings, and cutoff type (reduced power, warning light, warning buzzer, total shut-off etc), depending on the application; you wouldn’t want to loose all power with a plane or heli for example... When charging lipos, the balancer device is used to keep the voltage equal in all the cells of a pack- it can be a balancer that works along with the charger, separate from the charger, or you charge through the balancer. The end result is the same though- cells with a lower voltage get extra charge, whilst cells with a higher voltage get drained a little to keep them in line with the others. This is what the little white plug is for that you see sticking out of lipo cell packs, it is the balancing plug/tap. The lipo’s battery chemistry requires a special technique, called the CC/CV method (constant current/constant voltage). Basically, the charger will pump in a high current (amps) until the cells reach ~4.2v, then they will drop the current but maintain the voltage level until the cells reach and stay at 4.2v, at which point they are fully charged. Over charging is very dangerous, as lipo cells contain alot of energy, and overheating them can be a serious firehazard, hence the items called 'lipo sacks' that should be used to contain any possible damage caused by a burning lipo. The chances of that are rare these days though, and only idiots on youtube tend to burn up lipos for fun. Lastly, the C rating thing. This refers to a lipos maximum discharge rating, and is a multiple of its capacity. For example:

    A 20c 5000mah pack can put out 100amps.
    A 10c 8000mah pack can put out 80amps.

    Choosing the right capacity and C rating is important for any given application, and should be based on how many amps your chosen motor can draw at maximum load. For example, the feigao XL motors tend to draw about 80-100amps at peak current levels, so you should select a battery that can supply at least 80amps continuous. Generally though, the motors pull a continuous current of about 10-20amps or thereabouts, so the battery wont see very high drain rates for the whole run, otherwise it would soon over-heat and 'puff'. Once a battery puffs, its pretty much toast, though individual cells that are still okay can be salvaged- a 5s lipo can be reconfigured into a smaller pack of 4s etc. It is worth noting though that high mah capacity lipos with a low C rating at not as capable at discharging large amounts of current compared to a smaller capacity lipo with a higher C rating, this is because the voltage level droops heavily under a high load, due to the lipos low tolerance to high current draw; a higher C rating is always preferable regardless of the packs actual capacity. With the E-Revo, you are limited to a 8000mah 2s lipo, or 5000mah 3s lipo in each battery compartment, though specific sizes of packs vary, see below:



    EREVO BATTERY COMPARTMENT MEASUREMENTS

    A123 cells have a very high energy density like Lipo cells, but are inherently safer and 99% indestructible, so do not have to be used with an LVC (low voltage cut-off) device, and can be charged much quicker given the correct equipment is used. Their resting voltage is 3.4v, which makes a 5s configuration ideal for most applications that would normally use 12~14 Nimh cells, or 4s lipo. The downside is that they are limited to 2300mah or so of capacity, so ideally should be ran in a parallel formation such as 5s2p (2 five cell packs connected in parallel to double the Mah capacity but maintain the same voltage as 5 cells). They can be purchased easlily by buying a Dewalt 36v battery pack on Ebay, and then following one of the online tutorials which demonstrate how to turn them into RC packs. Mounting them in the E-revo requires some fairly drastic dremel work however.

    A new generation of prismatic LifePo4 (A123 chemistry) cells are currently hitting the market. These offer all the benefits of lipo cells in terms of power density and weight/size, but also have the benefit of safer chemistry, faster charge rates, no LVC required and capable of very hig current output without puffing or swelling. Currently there are only a handful of vendors for these new batteries; MaxAmps, Hobby King, and Protek being then main notable sources, though given the extortionate mark-up that MaxAmps charges (to pay for all its advertising and sponsorships no-doubt) I would stay clear of them until their prices drop inline with the competition... if they drop that is. There are other similar cells on the market, but most are low discharge, high capacity packs, unsuitable for R/C use. Time will tell on this type of battery, but if other companies start making and selling them for the R/C market, things will be alot brighter.
    Keeping the Mods busy is my specialty...

  4. #4
    RC Turnbuckle Jr.
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    17. Chargers and balancers

    Its important to choose a good battery charger that is suitable for charging your type of batteries. Do not go cheap, as you will inevitably want to upgrade to a better & faster charger in a short space of time. Ideally, you will buy a charger that can handle both lithium based and Nimh cells, that way you are ready for a lipo or A123 upgrade in the future without having to buy a new charger. A good charger will allow you to charge upto 14 cells or 6s lipo, and charge at a 1c rate (1c = batteries mah capacity, 1amp = 1000mah). This is important as some chargers have a lower wattage rating than others, and therefore must lower their charge current (in amps) when charging a high voltage battery pack, in order to stay within that wattage rating, EG:
    A 50watt charger will drop to around 3.5amps when charging a 4s (14.8v) lipo 4000mah pack.
    To workout how powerful your charger needs to be to charge a pack at 1c, simply multiply the fully charged voltage of your biggest pack, say 6s lipo (25.2v) by its capacity in amps, say 5amps (5000mah), which gives you 126watts. You will therefore need a charger that is rated for about 120watts or more, though generally speaking 50-100watts is more the norm that you will find in terms of mains powered chargers.
    If your charger is a DC type, it will need a power supply that is capable of outputting sufficient amps to power the charger, same rules apply basically when looking at power supply specs. An old PC is a good source for a good strong power supply, though it will require some modifications to serve its new function. Finally are balancers, which were covered before in section 16, but there is a little more to add. When choosing lipo or A123 battery packs with balance taps, it is important to concider the type of tap they come fitted with, as there are a dozen or so different brands/styles, and you may need to find a suitable adaptor so that your lipo battery can be balanced by your balancer. My advice is to choose the most common brand of tap when you are given the option (some stores allow you to choose the brand of tap you want fitted to your packs), and always choose that type whenever you buy new batteries. It is no great hardship to rewire a lipo pack, or to find a suitable adaptor, it just requires a lot of searching around and head scratching usually, but that is the nature of the hobby really; welcome to the wonderful world of RC.

    TUTORIALS

    CONTENTS:

    1. Lithium Batteries
    2. Brushless power systems
    3. Low Voltage Cutoffs

    1. Lithium batteries

    What voltage?
    What capacity?
    What size?
    What C rating?
    Which brand?
    What runtime?
    What charge rate?
    What about balancing?
    What about series vs parallel?
    Waterproofing?
    Puffing?

    What voltage?

    In the stock Emaxx, the Evx2 is equipped with a pair of battery leads, each one intended for use with a 2s lipo (7.4v), giving a total of 4s lipo (16.8v). It is best to use a pair of matching 2s lipos for space and weight reasons, but it is entirely possible to use a single 4s lipo. To do this, you must connect the 4s lipo to the BEC side of the Evx2, and then use a jumper to short circuit the un-used battery input leads. This diagram explains how:



    What capacity?

    Capacity is directly linked to runtime- the higher the capacity (measured in milli-amp hours, or Mah) the greater your runtime will be. Lipo cells in general are available upto about 5000mah in capacity, beyond this pairs of cells are used in parallel to increase the Mah, and therefore the runtime. The only downside is that larger Mah cells are also larger in size, and therefore weight (they are still only half the weight of Nimh cells it is worth noting however). Typical lipo packs are sold in 4000,5000,6000 and 8000mah sized packs, with the optional battery hold-downs being required for the larger sizes. The new Emaxx has more room for lipos compared to the old model, but aftermarket solutions are readily available to allow larger packs to be fitted to either chassis.

    What size?

    Since size is linked to capacity, it is worth ensuring that you can actually fit the lipos you wish to use in your truck. The very simple method of doing this is to just measure the length and width of the battery trays, and the height available with whatever hold-downs you have available. A Velcro strap is a simple way to allow taller packs to fit, but you are still limited in regards to length and width, unless you opt for an aftermarket chassis.

    What C rating?

    The C rating is also known as the discharge rating. This is a measure of how much current ( in amps) the battery can output before it will overheat and become damaged. Most lipos have the C rating listed in their specs, but this doesn’t actually tell you how many amps the lipo can ouput, there is a very simple sum however:

    Mah capacity x C rating / 1000 = output potential.

    For example, a 10C 5000mah pack can output 50amps, and a 20C 4000mah pack can produce 80amps. This however is assuming that the C rating on the pack is accurate. If you are in doubt, there is fool-proof way of determining the C rating, but it requires additional equipment. Using an Eagletree data logger or similar, you can record the voltage level of a lipo in relation to the amount of current that is being drawn from it. If the voltage level remains at about 3.0v or higher per cell at the specified C rate in amps, then it is accurate. If not, then it is over-rated. An example of this would be a 20C 5000mah pack outputting 100amps and staying at about 3.2v per cell. The graphs can sometimes be hard to interpret, but if you have the current and voltage graphs on the same chart, you can easily locate the voltage at any given current output.

    One important thing to concider when choosing a pack based on its C rating vs mah capacity is that 10C packs will drop their voltage heavily when taxed to more than about 12-15C (the typical peak or burst rating of 10C packs). A 25C pack will happily deliver in excess of 35-40C bursts before its voltage output drops, so dont always assume a 10C 8000mah pack will be just as good as a 25C 5000mah pack in a high-drain application; that would be a false economy. For low drain setups however where runtime is more important than current output, you would be fine with the lower spec, higher capacity pack.

    What brand?

    There are many lipo brands, several of which use the same specific company to produce their lipos for them, the only differences being the capacity and discharge rating options for any given lipo- horses for courses (meaning certain lipos are offered to fulfil a certain need or application, hence the differences between any given pair of lipos from two different manufacturers).

    The top name to look out for is Enerland. They are a Korean outfit producing the best quality cells that are used by numerous companies, such as those from RC LIPOS; the latest G3 packs are receiving rave reviews, and with good reason. Kokam cells are also very popular, as are the Flightpower and Trakpower lipos that resemble gold bars. Next on my list would be the increasingly popular Hobby King/Hobby City lipos, that come in a myriad of shapes, sizes and capacities to suit most people’s desires. SPC, TrueRc and the new Blue branded lipos from Hobbypartz.com are also very popular for the budget minded user. Maxamps lipos are very popular, but mainly due to the fact they advertise so much; they make lipo selection easy for beginners, but the price point is conciderably higher than it should be compared to other & better brands with a similar or greater spec.

    What runtime?

    Run time is also directly related to Mah capacity. Generally speaking, your typical 8000mah setup will run for approximately 40-60 minutes in a stock Emaxx, and around half that in a BL setup. It is very difficult to estimate runtime however as it depends greatly on the setup, terrain, ambient temps and driving style/ throttle usage; a full on speed machine will drain packs much quicker than a trail truck type setup.

    What charge rate?

    Lipos require a special type of charger that uses the CC/CV method (Constant Current/ Constant Voltage). Provided your charger is capable, you will be best served using a 1C charge that, meaning you charge the pack at 1x its capacity. A 5000mah pack will be charged at 5amps, an 8000mah pack at 8amps, and a 4700mah pack at 4.7amps. Some manufacturers will claim a 2C charge rate is possible for their lipos, but I would always recommend a 1C for safety reasons unless the instructions specifically state this. A123 cells or LiFePo4 can be charged at upto a 4-5c rate safely since they have a more stable chemistry.

    What about balancing?

    Lipo packs made up of more than one cell in series will require balancing. Lipo cells, no matter how good, will sometimes vary in terms of their exact capacity and discharge rates in relation to the other cell(s) in their pack, so it is important that any imbalance between cells is equalised during or after charging to prevent possible damage due to over discharging or over charging even. Where as a charger will pump current into the pack as a whole, only stopping when the target voltage is achieved, a balancer (or balance charger) will read the individual cell voltages and bleed off excess voltage/current from any cell that is getting ahead of its companions. Likewise, any cell that is lagging behind will receive extra current to keep it inline. The amount of current a balancer can add or drain varies, but around 300-500mah is fairly typical, meaning that small imbalances can be ‘fixed’ during a charge, but larger imbalances may require longer to correct before all the cells are at an equal level of voltage. The fully charged voltage of a lipo cell is 4.2v, so any higher than that and damage may occur; any lower than about 2.6~2.8v and damage will also occur; 3.0~3.2v is seen as the ideal minimum voltage before a lipo cell should be stopped from discharging. Storing lipos for long periods without use or cycling (discharge and charge) them may result in the cells becoming partially drained and out of balance, so checking them occasionally is recommended. Unlike Nimhs though, they do not need to be re-peaked or topped up if they haven’t been used for a few days, as lipos do not self discharge half as quickly due to lower internal resistance and superior chemistry.

    What about series vs parallel?

    Lipos wired in series (+ to – ) will increase the total voltage. For example, two 2s lipos wired in series will create a 4s lipo. The mah capacity will remain the same.

    Lipos wired in parallel (+ to +, - to -) will increase the total mah available, For example, two 2s 5000mah lipos in parallel will create a 2s 10,000mah lipo. The voltage remains the same.

    The 's' after 2s for example means Series, and is how many cells are wired in series within that pack (it does not stand for cells). The 'p' after 2s2p for example is how many cells are wired in parallel within that pack (if any). A 2s2p pack has four cells in total, with 2 pairs of cells wired in series to create a pair of 2s lipos, then they are wired in parallel to double the mah capacity. This is why some lipo packs in the 6000-8000mah range are often 2s2p or 4s2p packs which are rather large in size.



    When using batteries in series, the voltage can vary, but the mah capacity and c rating must be the same on both lipos (the age and condition too ideally). When using them in parallel, the the voltage, capacity and c rating must all be equal to prevent damage to the lower spec lipo thorugh over discharge.

    Waterproofing?

    Using some silicon sealant on the open ends of lipo packs that are covered in shrink wrap can help (you can sometimes buy them this way), but the main area for concern are the connectors that are not so easily waterproofed. Rusty balance taps will give inaccurate readings and cause issues when it comes to charging and balancing your packs. Best to avoid running lipos in or near water unless you have the initiative or imagination to come up with a solution to this problem.

    Puffing?

    This is a symptom displayed by lipos that have been over discharged. They will swell up and often become squishy to the touch, but sometimes also ‘deflate’ once cooled down. The easy way to avoid this is to choose properly spec’d lipos for your application, or to tone down your setup so that the lipos have some headroom in terms of what you are asking of them. Lipos that have only slightly puffed can still be used, bearing in mind the above piece of advice, but lipos that look like balloons afterwards are best either disposed of safely, or returned to the retailer for warrantee purposes. Safe disposal is generally considered as immersing the packs into a salty water bath to discharge them down to 0v, thus removing all their energy and potential to cause damage if punctured.
    Keeping the Mods busy is my specialty...

  5. #5
    RC Turnbuckle Jr.
    Join Date
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    Location
    England
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    2. Brushless power systems

    Why is BL better than brushed?
    Why does BL require lipos so much?
    Which brand of motor is best?
    Which brand of esc is best?
    What do all the numbers mean on these motors?
    Why is a feigao so cheap compared to most other motors?
    What voltage should I use with this motor?
    Why is high voltage better than lower voltage?
    Is there such a thing as too much power?
    Why cant I use the MambaMax system in my MT?
    I thought the MambaMax could only run on 3s lipo?
    Can I go BL for cheap?
    I have more money than sense, what do you recommend?
    What gearing do I use?
    Which type of pinion do I use?
    Where can I buy all this stuff I need?
    I can’t solder, what should I do?
    Do I need a different radio?

    Why is BL better than brushed?

    Numerous reasons. BL motors have far fewer parts to wear out, so maintenance is generally just a drop of oil on the bearings every now and then, and perhaps a blast of compressed air to remove any dust or dirt inside the motor. Because of this, your typical BL motor will last for years and years with constant use, where as brushed motors will require their brushes changed and coms skimmed etc etc.

    Why does BL require lipo so much?

    A BL motor the same size as your typical 550 motor is many times more powerful, but in order to make that power, it needs batteries that can supply it (in the form of high current flow, measured in amps). Nimh batteries are good for about 70amps or so, as I am reliably informed, but BL setups are much happier with more like 80-100amps typically; if the battery cant keep up with demand, it will rapidly overheat. In the case of nimhs, they explode, and lipos will generally ‘puff’; death by over-current in either case.

    Which brand of motor is best?

    Novak systems aside, then my personal list would go like this:

    1)Neu
    2)CastleCreations
    3)Lehner
    4)Hacker
    5)MedusaResearch
    6)TeamTekin T8
    7)HobbyWing
    8)Leopard motors
    9)Feigao

    Obviously there are many more brands and manufacturers, but those are the main ones you will likely encounter. My personal choice for a high budget build would be Neu, blue or black variety. For a mid range budget, I’d go for the Medusa or Castle motors, and then the Leopard motors for a low budget build. Feigao work fine, but they are prone to running hot and broken magnets are all too common compared to the better brands. Hacker and Lehner are European brands, so you are far less likely to find yourself buying one, plus the prices are somewhat astronomical. I missed PlettenBerg off the list since again, although they really are the best of the best, they cost more than your truck will generally speaking, so only uber rich dudes will find one of those on their shopping list.

    Which brand of esc is best?

    This used to be a tough call, but at present the Castle Creations MMM ( Mamba Monster (Max) ) is top dog in my opinion. It is a great esc, very smooth, great programming options, and very reliable.

    Team Tekin have the RX8 esc, aimed at the same kind of market as the MMM- 1:8 scale buggies & truggies, though it is slightly more expensive as Tekin is a racing team, so racing escs will always be aimed more specifically at racers willing to pay a bit more for what they use.

    The European MGMs are good escs also. They don’t have quite the programming options of the MMM, but they do have more options in terms of the voltage and current they can handle, so there isn’t a need to go with just one esc when a cheaper model will do what you require, and then some. That said, they are about twice the price of the MMM for comparable models. Some say they aren’t quite as smooth, but the updated software of late is the best yet.

    Quark monster pro 125b is something of an enigma, I think. Although spec’d as a 6s lipo esc, it is more at home with a maximum of 5s lipo due to peak voltage issues occasionally. It also suffers fro overheating issues due to its design (the case is the heat sink, and the PCB within can become detached, causing heat to become trapped); there are some clever fixes for this problem, but its not really worth it in my eyes as again, this esc is rather expensive, support is patchy at best, and it is of a lower spec than today’s MT oriented escs. Good luck finding a Quark plasma (Mk2 or mk3).

    Schulze is a name long associated with smoke and flames. They are the smoothest escs according to many, but the often poor customer support (so some say) would make me nervous of purchasing one, especially if the company that makes them would rather blame me for altering the connectors or having wires that are too long, rather than accept their product isn’t as bullet proof as they want to believe. Prices are also rather silly for what you get, and size is definitely an issue- huge pancakes of escs they are…

    Kontronik is another European manufacturer, but their top notch escs have far more positive feedback. The older Jazz models are better for high voltage & low kv motor setups, but their latest Jive line up is better suited to typical MT setups, as well as the HV route. Only issue is there is no reverse, only forwards and brakes, making this a good racer set up.

    HobbyWing XE-RUN 150amp & 80amp escs are a relatively new product from China, looking suspiciously similar to the MMM esc. They are much improved however over the older EZ-RUN escs that dwarfed the MMM but had various durability issues- not much cheaper than the MMM & MMPro escs, but certainly one to consider if every penny matters.

    The MambaMaxPro is another CastleCreations esc. Although it is intended for use in 1/8 buggies as a mild upgrade to the older MambaMax, it is a much more capable esc, capable of operating on 6s lipo & with sensored motors- only a slightly weak BEC lets it down, but this is solved easily with an external BEC unit. Just don’t use the cc36 motors as those wont cut it in a 10lb MT.

    Beyond that, most escs are either plane/heli items with no proportional brakes or reverse, or are intended for use in much smaller and lighter vehicles. Not that its impossible to use a forwards only esc, but it is best left to the guys doing BL conversions of nitro vehicles that use mechanical brakes.

    What do all the numbers mean on these motors?

    Let’s take a Neu 1515 1Y:

    15 = diameter of motor, in this case 39mm with the smooth can. Most BL motors of the 550 variety are 36mm in diameter.

    15 = length of the magnet/rotor. Other companies will use the second set of digits to denote the length of the can, which is often XL or 74mm for the kind of motors we need in MTs.

    1 = number of winds or turns, the fewer there are, the faster the motor is (higher kv rating (rpms/volt)). This also means the motor will draw more current, so beware.

    Y = type of wind. Motors are either Wye or Delta wound. Wye wound motors generate 1.73 times more torque than their Delta equivalent, but are also 1.73 times slower (1515 1 y = 2200kv, 1515 1 d = 4100kv).

    Longer motors will generate more torque in general, as will larger diameter ones. Feigao type motors are easiest to understand as they are generally sold as S, L an XL sized cans; anything with a diameter of 36mm being what you are after for MT use. Neu motors however have an advantage as they have 4 poles, vs 2 on the Feigaos. This important as a 4 pole motor will generate almost twice as much torque, all other things being equal. KV is a term you will see used often, and it refers to the number of RPMs per volt that a motor will spin; the higher the kv rating, the faster it will spin, but the more current it will draw too.

    Why is a Feigao so cheap compared to most other motors?

    Feigaos are cheap Chinese copies of Hacker motors. They are both 2 pole motors, but the quality and efficiency is much higher in the German made motors, as is true of the American made Neus and Medusas. Though the power output is more than adequate, the temperature and magnet issues are an unfortunate side effect; you must watch your gearing far more closely with the lesser motors than with the much more flexible and cool running better quality brands. As an entry level motor, they are a good place to start however if you are unsure what setup you are after, but don’t be fooled into thinking exotic water cooling solutions are the answer to keep a motor cool- that works in boats, not in trucks. A fan is much more simple, but often just masks the true problem, which is often a poor motor, bad gearing or poor overall setup choices.

    What voltage should I use with this motor?

    Although often argued about, I have a very simple set of basic guidelines that can be used as a general guideline for choosing which voltage to run any given motor on:

    1900-2700kv = 4s lipo
    1700-2000kv = 5s lipo
    1500-1900kv = 6s lipo

    Guidelines only. You can quite happily run a 2200kv motor on 5 or 6s lipo, but unless you gear down you will have a road missile. This sounds fun, but an uncontrollably fast truck can be quite dangerous, trust me; for speed runs only usually. I personally use a 2000kv motor on 5s lipo, and many others use the 2200kv Neus on 4s lipo. There is much potential for debate, but if you want a powerful setup that also runs fairly cool, then the 1900-2200kv range is best for 4-5s lipo. A high kv motor like the 1515 1.5d (2700kv) is best used only for 4s lipo, and a low kv item like the 1515 2.5d for 6s lipo. Since most easily available escs are 4-6s lipo, this should help make the decision easier, but as always, reading around and researching will yield far more info to aid you.

    Why is high voltage better than low voltage?

    There is a very simple equation:

    Power (watts) = volts x amps

    An MT requires a certain amount of power in order to move at a desired speed with a certain amount of torque. In order to generate that power level, you either require more amps and less volts, or more volts and less amps. Since current draw is one of the limiting factors with most if not all batteries and escs (not to mention wires and plugs), it is most wise to use a setup that draws less current and therefore more voltage. Obviously there is also a limit to the voltage you can use, but by simply choosing a 6s lipo setup and a slower, less amp hungry motor, rather than a 4s setup, you can make considerable improvements to your temps, runtimes and improve the lifetime of your equipment; repeatedly heating up electronic components will eventually kill them, sooner rather than later. A high voltage setup can be just as fast as a low voltage one, generate the same amount of wheelie-popping power, but will also allow you to often use lower spec batteries for the same given power levels. That said, if you simply increase the voltage without changing the motor, there is a higher load on the motor and batteries, which will reduce your runtime. If you gear down however to the same speed as you were achieving with the lower voltage, then runtime will increase some degree. Obviously there is a monetary issue that cannot be ignored with regards to choosing a higher voltage esc & batteries, but whenever possible, it is a route that should be exploited as it can save you money in the log run.

    Is there such a thing as too much power?

    Most would say no, but there is ofcourse. In a 10lb MT, you need a minimum of about 500watts to have 'fun', but most setups will be pushing the 900-1300watt region, with much higher peaks (under acceleration). Generally speaking, an XL or 1515 sized motor would be plenty, but for speed runs you might consider a larger 1521 or 1527 motor; these are truelly giants, but if you want to exceed the ~70mph world record for an Emaxx (HPI cheated with their touring car Wheelieking, bunch of goits), then you will need a lot of motor to do it.

    Why cant I use the MambaMax system in my MT?

    As it says on the CastleCreations website, the MM system is designed for use in 1/10 stadium trucks, such as the Traxxas Rustler, Stampede and Bandit sized models. The Emaxx and Erevo are nearly twice the weight, and 4wd, which places too great a load on the little CC36 motors. The same is true of the Traxxas Velineon/ VXL systems, only those are limited to 3s lipo, making them a far from ideal choice; the only saving grace is that they use a larger motor than the MM system, but still not big enough really.

    I thought the MambaMax could only run on 3s lipo?

    True. However, with a few simple modifications, it can be made to run reliably on 4s lipo or 12 nimh cells, or 5s A123. The built in BEC isn’t efficient enough at higher voltages than about 3s lipo to power the Rx and servo(s), so it can cause the esc to overheat and thermal. The solution is to take the load off of the BEC by removing the redwire from the Rx lead, and running an external power source. This can be either an RX battery pack that plugs into the Rx battery slot, or an external BEC/ UBEC, that taps into the main battery or batteries for power, and reduces that voltage down to something more useable before sending it to the Rx. A small 25-40mm fan is also very useful, and can be ran from the Rx if it is a ~6v item, or the main batts if it’s a ~12v item. Finally, it is recommended to use an extra capacitor to help the esc reduce its temps further, such as the older style Novak Hvmaxx power cap. However, any cap or caps totalling 2000-4000uf will suffice, but they must ideally be the Low ESR variety, and rated for 105*C in order to be of much benefit. Wire it in parallel to the main + and – wires, as near to the esc as possible. When this is done correctly, the esc will run cool and strong with most XL/ 1515 type motors, such as the 9XL or 1515 1y on 4s lipo.

    Can I go BL for cheap?

    Yes. A cheap reliable setup would be the MMpRO esc, a feigao 9XL, and a pair of mid-range 2s lipos. That should come in under about $250-300 for everything you need pretty much.

    A new HvMaxxPro system can be had for about $190 on ebay, and that will work fine with 12-14 nimh cells, as well as a pair of mid-range 2s lipos. A forwards only esc would be cheaper still, but the lack of brakes makes it a poor choice for a normal Emaxx or Erevo; a nitro conversion is a different story however.

    I have more money than sense, what do you recommend?

    A Plettenberg BigMaxximum, 6s lipo, MMM esc. Hold onto your hat…
    Keeping the Mods busy is my specialty...

  6. #6
    RC Turnbuckle Jr.
    Join Date
    Jul 2010
    Location
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    What gearing do I use?

    Gearing is made easy thanks to that nice bloke BrianG:

    TOPSPEED CALCULATOR

    Assuming you are wanting a fun, controllable setup, aim for 40mph with your setup. There are options everything you need to input such as differential ratios, transmission ratios, tire size, voltage, and specific motors. If your motor isn’t listed, you should know its kv rating however, so you can enter it manually, same too with your tire diameter and anything else such as spur gear size etc. All the options for Traxxas vehicles an feigao/neu motors are listed, so it shouldn’t be too hard to figure out. For a speed machine, a top speed of about 60-65mph is a realistic target, but it is easy to get carried away with the numbers you punch in, so remain sensible and be realistic about what your setup can do. A ~2000kv feigao on 4s lipo isn’t going to exceed 40mph without temperature issues; bumping up the gearing will only make this worse, as will using more voltage. Excessive heat on a motor is very bad news, and as a general rule, you shouldn’t exceed 180*F, or about 150*F on the esc, and 120-130*F on the lipos. This should be helpful as a general guide to gearing and temps:

    Hot motor + cool esc and batts = undergeared.
    Cool motor + hot esc and batts = over geared.
    Hot everything = way overgeared.
    Warm everything = correctly geared.


    Where can I buy all this stuff I need?

    Head over to the 'Truck links' page and you will find extensive links to numerous online retailers. Broadly speaking, besides the esc, motor and batts, you will require connectors for the motor to the esc (3 male and female bullet plugs, 5mm or larger), battery plugs of your choice, and some 10-12 gauge wire. As I’m biased, RC-Monster is a great place to get most things, but larger retailers like ImpaktRC and Amainhobbies also have most items. Shop around though, as many of the smaller boat and plane/heli webstores also carry the items you require, often at lower prices with more variety.

    What type of pinion do I use?

    Since the Emaxx and Erevo use 32pitch, or MOD 0.8 spurs, you require a 32pitch pinion (the difference between 32p and MOD0.8 is so small that they are interchangeable). Motors with a 5mm shaft will require 5mm bore pinions (that’s most BL motors from Feigao and Neu), motors with a 3.2mm or 1/8” shaft will require pinions with the same sized bore (bore meaning the hole in the middle). It is ill advised to simply drill out a pinion to increase its pinion size, as this can cause it to spin off centre, making a stripped spur or broken shaft more likely. MOD 1 pinions are most often used on nitro conversions, though they can also be used on purely electric vehicles when an especially small tooth count is required often, or when the user has issues with stripping the smaller teeth on 32p pinions. When mounting the motor, make sure the screws are not too long and do not touch the windings inside the motor. Also make sure that the mesh is not too tight, as this can cause binding that will heat up the electronics rapidly due to the high load place on the motor to spin the gears. A piece of thick paper placed between the spur and pinion before they are pressed together (meshed) will give just the right amount of clearance. If you cant feed paper in between them as you rotate the gears by hand, the mesh is to tight; if the paper goes in all to easily, the mesh is too loose. A tiny amount of backlash or play is what you are looking for, but it is important this remains the same as you rotate the gears, to ensure spur gear doesn’t bind with the pinion at any point in its rotation.

    I cant solder, what should I do?

    Learn. All you need to know really in order to solder is that you need a hot iron (60-80watts is more than fine, but 40watts is just about enough to do most things too, but takes a little longer), keep it clean with a damp sponge or brillo pad (you can buy special tip tinner and cleaner too), and use good quality lead free solder. A little extra flux often helps, but is often corrosive so be careful. When soldering things like deans plugs, be careful as holding the iron in place too long can cause the plastic housing to melt; soldering most connections should only take a second or two, to get in there and out again. If you visit Youtube, there are many great tutorials showing how to solder, and how useful tips and info on selecting the right iron etc, so do yourself a favour and study them; in this game, it’s pretty much essential knowledge.

    Do I need a different radio?

    Yep. AM radios and BL motors simply don’t mix 99% of the time, there is too much RF (Radio Frequency) interference generated by the motor and its wires. An FM radio (like I used to use) will yield much better results, but even that glitches occasionally & has a limited range. The best upgrade is a digital 2.4Gigahertz item. I cant speak for which brand is best, but as always, (you’ve guessed it) read around.

    3. Low voltage cutoffs

    What’s an lvc?
    What voltage model should I buy?
    Do I need one for each battery?
    What if there isn’t one for my voltage lipos?
    Which brand?
    How do I connect it up?
    Can I use it with Nimhs or A123 batteries?
    What about the other kind of LVCs?
    Where do I get one?

    What’s an LVC?

    Low Voltage Cutoff. It is a device that fits between the esc and throttle channel on the receiver (rx), and also connects to the power wires of the lipo battery. When it detects the voltage has dropped blow a certain level, it alters the throttle signal coming from the rx and prevents the esc from running the motor, thus preventing the lipos from discharging further. Different LVCs work in different ways; some kill the throttle altogether, some reduce the throttle power (known as soft shutdown or cutoff), whilst others are merely buzzers or flashing LEDs to warn the user that their batteries are running low. Either way, when the LVC begins to kick in, you should stop running the truck.

    What voltage model should I buy?


    This depends on a couple things:

    Does your esc have dual battery inputs or just a single + and – lead?
    Do you trust my advice more than that of other people?

    Point being that the Evx(2) and HvMaxx type escs (older model with no LVC built in) use a pair of 2s lipos, but each one has its own input lead to the esc. Now, these type of escs generally use one input lead/lipo to also power the BEC (Battery Eliminator Circuit- powers the esc’s brain and the servos/rx), so one lipo will discharge slightly faster than the other. If using an lvc that monitors the total voltage, it can be fooled into thinking that both lipos are still in the safe voltage zone, for example:

    One 2s lipo is at 5v, the other is at 7v = 12v total, but one lipo has cells that are at only 2.5v, which is dangerously low.

    To prevent this kind of issue, my personal advice is to run a single 2s LVC on the lipo that also powers the BEC, there by preventing either lipo from discharging below the safe voltage level. The BEC side of the esc can be found by plugging in a single 2s lipo to the esc; the side that activates the esc but wont run the motors is the BEC side- the non-BEC side will do nothing with a single lipo pack plugged into it.



    Do I need one for each battery?

    No. Since the LVC is connected between the rx and esc, you can only plug in one lvc device anyway; using a servo Y-harness to connect both lvcs to the rx will cause serious issues. Mainly, whichever lipo hits lvc point first will trigger the lvc to alter the throttle signal, but the lipo that hasn’t hit lvc point will have it’s lvc trying to send a normal signal to the esc via the rx at the same time; much potential for serious signal issues on the throttle channel resulting in an uncontrollable truck.

    What if there isn’t one for my voltage lipos?

    Well, most escs operating in the 5s lipo and higher region will have built in LVCs, such as the MGM and MMM models. However, occasionally you may want to use a separate lvc on your lipo, but there isn’t one that goes high enough (most are 2-4s items). The solution here involves the balance taps from your lipo. On a 6s lipo, there will be seven wires; one -, and 6 + (ordinarily, but check with a digital multi meter). What you need to do is take a female balance tap connector with wires attached, and locate the + wire that when combined with a specific – wire, gives you the voltage of a 4s lipo (14.8v, or 16.8v fully charged). You then connect the + and – from the LVC to these two wires, and when the voltage of these cells drops below 12v for example (3.0v per cell), the lvc will activate. Ofcourse, this isn’t 100% reliable as although it will work, it does mean however that 2 of your cells are not being monitored, and if they happen to be weaker than the ones that are being monitored, they could dip lower in voltage than the others. The best solution is an LVC that monitors individual cell voltages, but these are few and far between at the present time, although these items look promising:

    MaxPro 1-6s voltage checker
    Quanum remote voltage checker for 1-6s lipo

    Which brand?

    The most common and simple to install model is the Novak smartstop, in 2s, 3s and 4s flavour. Another good one is the True Rc ‘2s car lipo deep discharge protector’ that works in a similar way. A search of the airplane and heli websites will no doubt turn up other options, but you must be careful with some of them as they are not designed for vehicles that have a reverse throttle setting; this is very true of the Dimension Engineering LVCs.

    How do I connect it up?

    Very simple usually. The LVC itself plugs in between the esc and rx throttle channel, and then there is normal a + and – wire that goes to the power input wires of the esc (battery leads). This is where you have a couple options:

    1) if you are using a dual battery input esc, then use a 2s LVC and wire it as I described earlier.
    2) if you are using a single battery input esc, then wire the LVC to the the esc side of the battery plugs/connectors.

    Some LVCs will use a balance connector rather than the + and – wires, so this plugs into the lipo’s balance connector to monitor the total voltage or individual cell voltages; its manual will be more specifc and include its own wiring diagrams.

    Below are a few possible LVC setups using various escs & battery configurations (note that the hvmaxx and evx type escs are wired the same for battery inputs, so what works for one also works for the other):



    4s lipo using a single battery input and dual 2s lipos in series.



    4s lipo using a single battery inout and single 4s lipo.



    4s2p lipo using a single battery input and a pair of 4s lipos in parallel.

    Can I use it with Nimhs or A123 batteries?

    Not required for Nimhs, and A123 type cells operate at a different voltage to lipos, 3.3/3.65v per cell rather than 3.7/4.2v per cell. This means the LVC will kick in much too soon. Ordinarily though, you don’t need an LVC with A123 cells as when they reach the nearly discharged point, they drop in voltage very quickly, meaning you notice the lack of power and can stop the truck. Also worth noting that A123s are much more tolerant to over discharging and fast charging compared to lipos, but that is covered more in the FAQ if you care to read further.

    What about the other kind of LVCs?

    Well, there are more unorthodox options for LVCs out there if you so desire. I myself use an item that lights up an LED when the voltage dips below 12v for a 4s lipo (3.0v per cell):

    BRC Hobbies lipo battey saver

    There are also a few similar type items from Swang hobby, True RC and Maxamps:

    Hobby Hot voltage checkers
    TrueRC voltage checkers


    Worth noting these are generally considered as ‘passive’ devices, meaning that they wont normally stop the truck from running, but instead just warn the user when their lipos are becoming discharged. An audible alarm is generally better than a visual one, but it depends on how good your hearing, eyesight, and common-sense quotient is….

    Where do I get one?

    Most online retailers such as MaxAmps, Amainhobbies and TowerHobbies will carry LVCs, but it is worth looking further afield for some of the more ‘exotic’ options. HobbyHot, BRCHobbies and TrueRC have them, but as always, Google is your friend.


    For more technical information links and 'How-to' guides regarding the Traxxas trucks and Batteries etc, please visit the 'Useful links' page on my website ( CLICK ).

    NB: E-Revo 5603, 5605 & 5608 share 99.9% of the same parts- only the motor, esc &/or radio differs between each model.
    Keeping the Mods busy is my specialty...

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