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Thread: Help New LiPo

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    Help New LiPo

    Hi guys so im new around here and to vxl and I just ordered a Velineon brushless 1/10 system. The kit with the esc and motor and all that and a new battery and charger. I ordered a venom 3s 11.1v 4000MaH 20c batttery and some traxxas charger which i think is broken but im not really worried about that. But my main question is assuming when these things come will my battery be sufficent for the Velineon motor and esc? what sort of speeds can I expect in a Bandit with a 31 tooth pinion and 76T 48P spur gear with stock everything else? I began reading about c ratings and volts and what they all do but I just got very confused, help a beginer out please

  2. #2
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    The battery will be able to provide only 80 amps... so I fear it is not enough for the V3500 power system due to from what I read it is quite amp hungry.

    How I came to this figure:
    mAh x C rating / 1,000 = Available amperage
    So...
    4,000 x 20 = 80,000 / 1,000 = 80

    Also, from what I read Venom is not a real trustworthy brand.


    Here is a speed calculator.
    This should help you get close to some real world speed estimations.




    Hopefully this next section will help resolve some LiPo questions:

    I apologize in advance for the length of this write up. However, I feel that it is important to have as much factual LiPo information as possible and to have it all in one location. Try not to get overwhelmed... just take it in bit by bit.
    That being said...

    LiPo 101
    now in session


    Rules
    1) NEVER discharge below 3v/cell
    2) NEVER charge above 4.2v/cell
    3) NEVER puncture your pack
    4) NEVER short out your pack
    5) NEVER use a pack that has puffed
    6) NEVER charge unattended
    7) NEVER charge at a higher C rate than recommended
    8) NEVER use a pack that has been over charged/discharged
    9) ALWAYS check cell voltage before connecting your pack to anything
    10) ALWAYS keep your LiPo pack well balanced

    To calculate the charge rate of your pack
    mAh x charge C rate / 1000 = charge amps
    For example:
    A 2200mah 20-40C pack that states a 2C charge rate.
    2,200 x 2 / 1000 = 4.4
    This battery pack can be charged at 4.4 amps.
    - Please note that if no charge C rate is stated, 1C is standard.

    To calculate the constant discharge rate of your pack
    mAh x minimum discharge C rate / 1,000 = available amps
    For example:
    The same 2200mah 20-40C pack.
    2,200 x 20 / 1000 = 44
    This battery pack can consistently provide up to 44 amps.

    To calculate the peak/burst discharge rate of your pack
    mAh x maximum discharge C rate / 1,000 = available amps
    For example:
    Again, the same 2200mah 20-40C pack.
    2,200 x 40 / 1000 = 88
    This battery pack can provide a peak discharge rate of up to 88 amps.
    Peak rates are limited in time... unfortunately, this amount of time does not have an industry standard. This is how a lot of inflated discharge ratings can be claimed. In my experience, honest retailers/manufactures of packs will list the constant discharge rating along with the burst discharge rating and not only the burst rating.

    Ratings
    When setting up your power system for your RC, make sure that the lower discharge C rate matches or beats the continuous amperage rating of the ESC. I try to beat it by at least 10%. This practice will provide you the most out of your system and it will also keep your batteries from working too hard. A LiPo should NEVER be hot... during use or charging. If it is, you are abusing the pack. Also, the less your pack has to work the longer it will last. However, LiPo's perform at their best once they are between 100F - 120F. (yet another reason to have a temperature gun)


    Parallel
    Running two LiPo's in parallel will double run time and also your available amperage... which is handy for high demand systems. Some misinformation I have read about the discharge C rating of packs in parallel is that the rating of the pack doubles. This is not the case. The C-rating of a battery pack is a fixed parameter of that pack; well actually it is the cells within the pack that have the C rating. Connecting two packs in parallel does not change either pack as they still have the same specifications, however it does create a battery "system" with twice the effective C rating. The packs are the same, but the parallel system is now theoretically capable of discharging at twice the Amp rate. This is much like the cumulative capacity available when connecting two packs in parallel.
    The packs ran in parallel MUST be of the same cell count and should be the same age, capacity, and brand.

    Series
    Running two LiPo's in series will double voltage, therefore nearly doubling the speed of your RC. Capacity remains the same. The two packs ran in series MUST have the same capacity and discharge rate. Also, they should be of the same age and brand.
    Be prepared to gear down when increasing voltage on your power system.

    Charging
    There are many charging options out there... it can get really confusing really fast. The best advise I can give is to get the absolute best charger you can afford and to ask before you purchase. Your charge system is the backbone of your electric RC hobby, treat it as such. RC's will come and go, but your charge system will remain.

    The following features are what I consider to be the absolute bare minimum for a charger... balance charging and a storage charge/discharge feature. If the charger cannot perform these tasks, look for another charger. If you are going to be charging multiple LiPo's at the same time or 10th scale or larger packs, I recommend getting a charger that is capable of at least 10 amps or more. Also, ANY half-decent charger can charge multiple LiPo's at a time. It does not require a dual or multi-charger to perform such a task. It only requires the right support equipment... such as a ParaBoard, which I use.

    Storage
    Storage voltage is 3.85v/cell. This voltage is the only voltage that is not super critical for LiPo. Anywhere between 3.5-4v/cell is considered to be acceptable for storage.
    I suggest putting a full pack to storage voltage if it is not going to be used within 30 hours or so. The longer a pack is at full capacity, the shorter its lifespan will be.
    I also suggest bringing a pack up to storage voltage after a run. When a LiPo's voltage lowers to a certain point, they begin to loose their voltage quickly. I would hate to see you loose a pack (or more) due to not charging up within a few hours after a run.
    For long term storage; I bring my packs to storage voltage, seal them in an airtight container, and stick them in the refrigerator. As I type this, I have had my "speed" set of 3S packs in the fridge for over 8 months at storage voltage... I check them monthly and they are still at 3.85v/cell. Almost makes me regret buying them. lol

    Making your LiPo's last
    I will just give an example of how much a small change in how a pack is taken care of can dramatically change how the pack behaves.
    Two identical packs were both charged and discharged in the exact same matter.... except one pack was charged to 4.20v/cell and the other to 4.10v/cell. This was done in a very controlled environment... NOT in an RC.
    After 500 cycles, the pack that was charged to 4.20v/cell had reached its life expectancy... it would not take more than 65% of its original capacity; meaning the LiPo was no longer able to be used safely.
    The pack that was charged to 4.10v/cell was still at 70% capacity after 1,000 cycles... so the .10v/cell difference more than doubled the life expectancy.



    Here is what I have done...
    this information might help with your decision

    I use inexpensive batteries.
    I have found them to be very reliable, extremely cost effective, and they have been proven to be under-rated; usually providing more mAh and a higher discharge C rate than stated on the pack. SPC is a great brand that under promises and over delivers. There are others that claim extreme discharge ratings that are simply impossible with the technology that is available.

    I use an iCharger 206B.
    When I purchased the charger, I thought I would never use all 20 amps of its capability. Well, now I rarely charge at anything less than 20 amps lol. I have even considered selling it to get more amperage! I have performed hundreds of charge cycles with this charger and it handles the task without a single issue.
    I highly recommend any charger in the iCharger line.

    I built my own power supply.
    I have ~$30 into my 24v 75a 1800watt power supply.
    Sounds complicated, but it really is not that difficult. If you go this route, you are going to want a server power supply as they do not drop voltage when you are pulling amperage like a standard ATX PC power supply.
    You can also purchase these pre-built at a very reasonable price.

    I hope this information helps!!

    Here are some links to some more:
    http://traxxas.com/forums/showthread...rger-vs-cooker
    http://traxxas.com/forums/showthread...charging-setup
    http://traxxas.com/forums/showthread...ply-Conversion
    Whatever it is I just said... I could be wrong.

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    So if its not enough to power it what is it going to do to the system ? and yea through my research i ended up finding most people say its a bad brand but I was on a budget and it looked well made and sounded convincing :/ I got the battery and stuff today though and ran the car it seemed to really rip. I did however get a early lvd cutoff and turned the battery back on

  4. #4
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Starve the motor... possibly cause ESC damage... definitely cause LiPo damage; which will cost you more in the long run.

    How much did you spend on the Venom?
    The reason I ask is here are two viable options for the Bandit for $40.95 from a very reputable company:
    http://spcracingbatteries.com/index....&product_id=55
    http://spcracingbatteries.com/index....&product_id=58

    The first one is capable of 172 amps and the second 200.


    The early LVD cut off is a sign that the battery is severely dipping in voltage due to not being able to keep up with amp demand.
    Whatever it is I just said... I could be wrong.

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    38$ So what would you recomend I do keep running it for a while till I get more money for a good enough battery, are the chances of damage that high ? I saw plenty of 5 star reveiws for that battery on amazon and they were running V3500's. And what is the difference between hard case and soft case? I will definately purchase that second one in the future though
    Last edited by proskibum1999; 10-07-2013 at 06:19 PM.

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    Quote Originally Posted by proskibum1999 View Post
    38$ So what would you recomend I do keep running it for a while till I get more money for a good enough battery, are the chances of damage that high ? I saw plenty of 5 star reveiws for that battery on amazon and they were running V3500's. And what is the difference between hard case and soft case? I will definately purchase that second one in the future though
    Hard case basically come with a outer shell which adds to the durability of the pack. I personally like my hard case packs. The pro to a soft case is that you can see if the lipo puffed much easier and it will generally fit in battery bays easier IMO.
    Rustler VXL | Slash | Stampede 4x4

  7. #7
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Hard case LiPo's are in a thin plastic box to help protect them from damage... like little stones that get in between the pack and the chassis of open chassis RC's. A little stone can ruin a LiPo by puncturing the pack. Depending on your terrain, it might not be a bad idea to run a hard case.

    If it were me, I would see about returning that Venom pack. The last thing anyone needs is a LiPo flare out to deal with. I would hate to see you waste the money, burn yourself, burn your RC, or even burn your house.

    As far as good reviews... some just don't know any better. For instance, if the only way you have ever driven a nail is with a rock, that is the best way... until someone hands you a hammer.
    Whatever it is I just said... I could be wrong.

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    I got a question Jimmie, under the Storage section, you saying that the pack should be charged up to storage level after a run. So do I only do this when it hits LVD or only when the pack's voltage is out of the 3.5-4v/cell range?

    Also under Making your Lipo last section, about the .10v/ cell difference, if I charge my at 4.10v/cell every time its life last longer, but in turn slightly less run time, so am I right or is it only when I cycling my pack?
    Did you say Traxxas?

    Yes with or without lipos.

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    It was an ebay purchase so I will look into returning it immediatly after this weekend and purchasing most likely that soft case model battery as I mostly bash on just dirt and asphalt. Thanks for your help guys

  10. #10
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Souper:
    When the pack is out of the storage voltage range.
    If you are not going to be using it within the next 24 hours I would put the pack somewhere closer to 3.8v/cell.

    Every time to 4.1. However, some early testing is showing that a LiPo will only last so long no matter how well it is treated (within reason)... 3-4 years is the hypothesis right now, but that could change as testing progresses.
    Also, there is no reason to cycle a LiPo pack. Yes, it does have a "break in" period when it should be treated nicely during charging and usage for the first few runs, but just cycling it on a charger/discharger really just wastes charge cycles.

    Pro:
    Glad to help when I can! Hopefully the pack works out to your favor... if they don't take it back you might be able to sell it on eBay or something if you wish.
    Whatever it is I just said... I could be wrong.

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    Thanks Jimmie, so what your saying is that I don't have to cycle a lipo that was in long periods of storage that have not been used for quite some time?
    Did you say Traxxas?

    Yes with or without lipos.

  12. #12
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    That would be a different story...


    That type of cycling is to keep the chemistry active... it also means you aren't running your RC enough. lol
    Whatever it is I just said... I could be wrong.

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    Ok just wanted to make sure that I don't take it the wrong way. So only cycled it when it need it, right?
    Did you say Traxxas?

    Yes with or without lipos.

  14. #14
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Yes.
    Some old habits die hard... NiMH and NiCD needed regular cycling to retain capacity, but this is not needed with LiPo.
    Whatever it is I just said... I could be wrong.

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    Ok then, thank you so much.
    Did you say Traxxas?

    Yes with or without lipos.

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    Hey Jimmie about that new battery I wanted to know what I can expect from it? will it be any more powerful? and will it last at least 30 minutes or so ? I have the venom ready to be returned

  17. #17
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    It will have more punch, so it will get up to speed faster as long as there is traction. Top end will be about the same because the voltage is the same. The SPC may be a bit faster due to voltage dipping less because it is capable of more amperage than the Venom.

    It should last 30 minutes... more or less. I don't have an RC as light as a Bandit to be able to tell you for sure, but a 5,000mAh 5S lasts about that in my 12 pound 1/8th scale so I imagine you should at least get that out of it.
    Whatever it is I just said... I could be wrong.

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