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  1. #1
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    Some real Nooby Battery Questions

    Hey guys,

    So I bought a Rustler VXL about 5 years ago, and I had just decided to dig it out of my closet this afternoon. I've got three NiMH Venom batteries -- two 7 cell 8.4v and one 8 cell 9.6v. I've also got a Triton EQ charger which my local Hobby Shop (who sold it to me years ago) couldn't even recognize. I tried to do a charge/discharge cycle as instructed by the charger manual and the batteries haven't seemed to come back to life. They were functioning well when I left them years ago. However, I believe they're toast and I need to purchase some new packs. After a little bit of research I've read Venom's aren't the best? Back when I bought these guys they were $72 and $94 respectively and they've dropped tremendously in price, which was nice to see. Is there a better NiMH alternative with the same power? Any help would be greatly appreciated.

    Thank you
    Last edited by diistinctive; 11-25-2013 at 02:46 AM.

  2. #2
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    The days of NiMH are numbered... which means that there are not many competitive companies producing what was considered great packs. With all the research I did, Venom very rarely was mentioned in good favor... so I believe you are correct with the thought that they are not that good of a pack. If you must stick with NiMh, I suggest finding some Traxxas packs.

    Funny how battery tech can change over the course of time? $70+ for a NiMH used to be the norm... now you can get LiPo packs that have more than double the amperage capabilities and double the mAh for less!

    If you decide to take the jump to LiPo... we are here to help!


    Also, I would consider your packs to be a loss... there are high end chargers that might bring them back to life, but they wouldn't perform as they should and are probably more of a risk than a gain.
    Whatever it is I just said... I could be wrong.

  3. #3
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    I really appreciate your knowledge and help. It's funny to see how the technology has changed, but if LiPo batteries are the way to go then I guess I could try them out. Back when I got the car I was told that they were terribly dangerous and explode (perhaps just a biased salesman) but if they can run safely then I'm willing to give them a try? What would you guys recommend to get started with LiPo? I really don't feel like breaking the bank again with batteries because I don't need the car to go 90+... I know the charger I have can handle them, they're just a little foreign to me. Thanks again.
    Last edited by diistinctive; 11-25-2013 at 05:16 PM.

  4. #4
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    It is good that you have a LiPo ready charger... that will make the switch even cheaper!

    There are a few rules to follow to stop any bad things from happening... once you understand them they become second nature and are followed without even really thinking about them.

    Most of these rules are followed by proper charging.

    1) NEVER discharge below 3v/cell
    --- Use a LVA (low voltage alarm) if your ESC is not LVD (low voltage detection) equipped. Set it for at least 3.4 volts per cell. After that the rule is followed automatically.
    2) NEVER charge above 4.2v/cell
    --- This should be a setting within the charger... once it is set, this rule is followed automatically.
    3) NEVER puncture your pack
    --- A bit of common sense here... but if one does get punctured for one reason or another, don't use it.
    4) NEVER short out your pack
    --- More common sense... if it has been severely shorted out it is probably damaged and should not be used.
    5) NEVER use a pack that has puffed
    --- Puffing is a sign of damage. Damaged packs should not be used.
    6) NEVER charge unattended
    --- That way, if something does go wrong you are there to correct the issue before too much damage is done.
    7) NEVER charge at a higher C rate than recommended
    --- While it is tempting to be done charging just a little sooner, those limitations are set in place for a reason: safety.
    8) NEVER use a pack that has been over charged/discharged
    --- It is a recipe for disaster... most of the bad LiPo reputation comes from abused packs and this is the most common abuse.
    9) ALWAYS check cell voltage before connecting your pack to anything
    --- This will allow you to know the health of your pack... and not a bad practice to get into. Checkers are like $5.
    10) ALWAYS keep your LiPo pack well balanced
    --- This can be an automatically followed rule if you balance charge every time. Most of the "LiPo's are super dangerous" knowledge is from when chargers did not balance charge. The further a pack is out of balance, the easier it is to break rules 8, 2, and 1.

    I have heard lots of bad advice from a Hobby Shop... mostly from ignorance but probably partially from wanting to sell what they had over what they would have to order. The one that just closed up used to inform their patrons that LiPo packs needed to be treated as if they were containers of nitroglycerin.... and the are really no more dangerous than NiMH.


    Here is a pack that will work great in a Rustler:
    http://spcracingbatteries.com/index....rice&order=ASC

    SPC is a rare company... they combine a great battery pack with awesome ratings at a price that beats out the lesser competition.

    If you want to keep it Traxxas:
    http://buy.traxxas.com/product_info....oducts_id=5349


    Of course, there is a whole lot more info on LiPo... if you want more knowledge, just ask!
    Whatever it is I just said... I could be wrong.

  5. #5
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    Wow thank you so much for all the help. Surprisingly I got my 8 cell NiMH to nearly 2500mAh and it ran for a little while, but I'd like to get the car running at full capacity with another battery.

    As far as what battery to buy, the $26.95 pricetag is nice, but remind me again of the C value and is there any significant advantage to getting the 5000mAh, 40C, 2S, 7.4V pack for $30.95? This is all so much cheaper than spending the $70+ for the ancient NiMH so $5 isn't too much of a difference.
    Maybe in the future, I could invest in this guy? If my Rustler can handle it?
    http://spcracingbatteries.com/index....&product_id=67 ( 5000mAh, 40C, 3S, 11.1V Soft-Case)
    Would my car be able to handle the voltage coming out of it? My understanding is the voltage translates into the power, and I think it'd be nice to get that much more out of the car if possible.

    Thanks again Jimmie Neutron.

  6. #6
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    What ESC is currently in it?

    2S = 8.4 volts fully charged
    3S = 12.6 volts fully charged

    If your ESC can handle the above voltages, it can handle 2S and 3S packs. But, be forewarned that the power that LiPo delivers over NiMH is insane. Amperage delivery is consistent throughout the run, unlike NiMH that continually drop off from the first pull of the trigger. I would start with 2S... I too, thought I wanted the most power available when I bought packs... but honestly, the 2S packs were more than enough to have fun and it seems I was always breaking something with 3S power.

    Voltage translates to speed more than it does power... at least with my definition of it. Power is more like amperage capability to me... how fast you can get to speed... more than how fast it can go.

    The C rating will allow you to figure out the amperage capability of the pack using a simple formula:
    mAh x C / 1,000 = amperage

    So, using this:
    5,000 x 30 / 1,000 = 150
    5,000 x 40 / 1,000 = 200

    If the pack is capable of more amperage than your power system draws, there is no need to get a more capable pack. You can base this off of the ESC's capability... you want to at least match the ESC's ratings plus 10-20% so the pack is not working to deliver the fun.

    Also, with an open pan RC I suggest a hard case pack. There is nothing worse than bashing around and having a small little pebble puncture your pack and forcing you to buy another... been there, done that; only got 1 run out of a $60 pack!
    Whatever it is I just said... I could be wrong.

  7. #7
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    I've got the VXL-3S ESC.
    So which of the two would be best?
    I'll take your word on the 2s vs. 3s packs, and hard vs. soft. Matter a fact I'll take your word on almost anything (RC related) haha.
    It looks like I'll start off small and I assume I should just pick up a LiPo charging bag from my local shop for safety..

    If I go to purchase these packs, my only question lies with discharging.. My charger balances while it charges so that doesn't seem to be an issue, while discharging to me it doesn't seem as straight forward as with NiMH. My charger has a recommended 6.0V cutoff voltage for 2S packs? How many amps should I discharge them at considering my charger can do it from .1A - 1.0A. How often do I need to discharge?

    You've been an amazing help.
    Thank you.
    Last edited by diistinctive; 11-25-2013 at 09:57 PM.

  8. #8
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    You only need to discharge if voltage is too high for storage... LiPo's should be stored around 3.8v/cell. Any lower and they could over discharge themselves ruining the pack and any higher the cells are under stress shortening the life span of the pack. For long term (over 2 days) I make sure the voltage is right at 3.8v/cell... for shorter periods I use anywhere from 3.6-4 volts per cell as a goal.

    Most chargers have a storage feature for LiPo's... does yours?
    If so, just set it up as if you were doing a balance charge... the only difference would be that the charger is in storage mode and not balance charge mode. You can discharge the pack at a much higher rate than the charger is capable of, so set the max discharge rate according to the chargers limits.

    LiPo's do not need cycling... ever. Just charge, use, and store at proper voltages. You can even use the pack from storage voltage down to the minimum... LiPo has no memory effect.

    The 3S ESC is known to have some issues handling 3S packs... just a word of caution, as you might end up needing a new ESC if 3S is what you want to run.

    Glad I could help!
    ~J
    Whatever it is I just said... I could be wrong.

  9. #9
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    My charger doesn't have a storage feature for LiPo's just charge and discharge. In its discharge setting you set the charge current and voltage. I know I won't be using this thing everyday and will probably need to store it most of the time, so I would need to discharge it to the right setting. It also looks like I'm going to purchase a 2s. I guess that would be 3.8x2=7.6v for storage? This doesn't add up to me because it charges at 7.4v?

  10. #10
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    A 2S charges up to 8.4 volts... the voltage listing on the pack is nominal, just as it is for NiMH or even NiCD.

    I don't see where the charger would harm the pack discharging in NiMH mode as long as voltages are watched closely. You don't want to over discharge the pack.
    Whatever it is I just said... I could be wrong.

  11. #11
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    I guess I'm missing something but I thought they charged to 7.4v, "5000mAh, 30C, 2S, 7.4V Hard-Case"?
    Either way, this might help you understand what I'm working with. This is from a page out of the manual concerning the graphic for LiPo's.



    The second row is of the discharge settings. For storage would I just set it to ... ?

    Thank you again for your patience..
    Last edited by diistinctive; 11-26-2013 at 12:33 AM.

  12. #12
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    That discharge setting would work... as long as the voltage can be changed to 7.6 volts (3.8 x 2).

    Remember the max voltage per cell? 4.2 volts... 4.2 volts x 2 cells = 8.4 volts. The nominal voltage for a LiPo cell is 3.7 volts. The reason 7.4 volts is on the pack is packs are labeled with nominal voltage... 3.7 x 2 = 7.4. Just like your NiMH packs are labeled with nominal voltage... which is 1.2 for NiMH cells. The 7 cell packs you have that are labeled 8.4 volts were actually 10.5 volts when fully charged as the approximate full voltage for a NiMH is 1.5-1.6 volts per cell.
    Whatever it is I just said... I could be wrong.

  13. #13
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    Okay, thank you again for help and patience. It means a lot.

    The discharge setting can be changed from 6.0v.
    I was just thrown off by seeing the 7.4v Charge setting because that can only be changed by increments of 3.7 to 11.v and above.

    Unfortunately, I'm into instant gratification and on the West Coast so purchasing from SPC will take a couple days. My local shop still carries Venom products so their Venom 20C 2S 5000mAh 7.4 Hardcase LiPO Battery would be the one I'd purchase.. Is 20C too low in comparison to the 30C from the SPC pack? Would there still be that much of a difference over the NiMH batteries in their prime? I'm willing to dump the extra cash on it considering it's just waiting on a shelf right around the corner.

    I swear I'm nearing the end of my silly questions...

    Thank you.
    Last edited by diistinctive; 11-26-2013 at 12:38 AM.

  14. #14
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    The 7.4, 11.1 increments are dummied down settings to help reduce confusion for un-knowledgeable people that just go by the print on the pack. I think it adds more confusion!

    I would stay away from Venom.

    There is another tidbit about C ratings... there is no industry standard. What this means is that two different companies can get the same pack... one company can decide to call it a 10C pack and the other can decide to call it a 20C pack; there is nothing stopping them from doing so. The companies I recommend have proven themselves over and over that they honestly rate (or at least under rate) their packs.

    What this boils down to is that Venom pack may not actually be a 20C pack... it could be a 15C... or a 10C...
    SPC packs are exactly what they state or more. Battery guru's from other forums have tested them and Traxxas packs and each time they exceeded the rating of the pack; meaning you are getting more than what you pay for.

    SPC is worth the wait...
    besides, it has been how long already?? lol
    Whatever it is I just said... I could be wrong.

  15. #15
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    Alright, yeah I did read about company by company C ratings differing. Thanks for directing me in the way of the good ones.

    I'm back from school on break for Thanksgiving and just want the thing going again. I did get my 8 cell NiMH to 4000mAh so the car does run and I'll have that hold me over until I get the SPC. You might as well be in their sales department haha.

    I think you've helped tremendously and really the only thing I'm unsure of now is just general use.

    When I get the battery it's at a storage charge and I'll need to plug it in and get it to 100%?
    From there I run it down to low voltage detection, and wait for it to cool and toss it back onto the charger?
    Do I have two choices at this point, discharge it to 7.6v (for storage) or charge it up to 8.4v? Or will the LVD be lower than 7.6v so I will have to charge it up, and then lower it to 7.6?..
    How long can I leave the battery charged at 100% before it will begin to damage itself? I assume this is less than two days?
    If I use the battery, but don't run it all the way down to LVD can I charge it up to 100% from just minimal use, what are my options? Are they just the same as if the battery was charged, or do I need to run it down to LVD?

    I'm really just trying to come full circle on this so nothing can every go wrong.
    Thank you again good sir.

  16. #16
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    Sorry guys, but this is not a Traxxas NiMH thread, so it must be closed.
    Alt-248 on the number pad =

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