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Thread: batteries!!

  1. #1
    RC Racer
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    Question batteries!!

    Ok guys, i have the 1/16 summit brushed. I am looking to get another set of batteries. I usually use two series 1, 7.2V batteries at one time. I want something that will run good but won't overheat my motor and esc.... I need something with a long run time because I will be at the track.

    Thanks,

  2. #2
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Are you ready to go LiPo?
    That is about the only way you are going to get a significant amount of run time. I think the largest NiMh that will fit is 1800mAh, only 400 more than stock.
    Whatever it is I just typed... could be wrong.

  3. #3
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    which lipo would do the best, but would not cause overheating?

  4. #4
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    In my opinion, SPC 2S 2500mAh 50C packs are the best bank for the buck.
    There are cheaper, but you will sacrifice either customer support or quality... probably both.
    There are more expensive... why buy more expensive?? lol
    Whatever it is I just typed... could be wrong.

  5. #5
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    so they are less quality than other batteries? and what kind of power do they give?

  6. #6
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    I believe them to be of top quality.

    Here is a comparison between a 6 cell NiMh and a 2 cell LiPo:

    If you took two identical RC's and two identical RC drivers, with the only difference being the batteries... in the beginning of the race the NiMh will probably be faster. But, by the end of the first few laps (and sometimes not even that long) they will be neck and neck because the NiMh's voltage has dropped to match the LiPo's voltage. As they continue to race, LiPo's consistent voltage and amperage availability will allow the LiPo powered RC to pull ahead and win, meaning at this time LiPo has the higher voltage and the higher amperage availability. If the track is really twisty and forces the driver to slow down and power out of corners, the superior amperage availability of the LiPo will actually beat out the higher voltage of the NiMh and the LiPo would not fall behind, even in the beginning.
    Also, if you want to take into account weight and dimensions; the same capacity LiPo is probably going to be about half the weight. If you match the weight, the LiPo will be about twice the capacity... meaning that while the NiMh is being charged (and NiMh can only be safely charged one at a time vs LiPo's capability to be safely charged in multiples) the LiPo still has enough capacity to race another heat... or two.
    Whatever it is I just typed... could be wrong.

  7. #7
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    so basically go lipo.... i found a track right next to my house so ill probably be joining in... and im guessing only run one at a time!

  8. #8
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Single = good
    Parallel = great
    Series = BAD

    You can probably get 40-45 minute run times with a single 2500.
    Whatever it is I just typed... could be wrong.

  9. #9
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    whats the difference between series and paralell?

  10. #10
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    Series: doubles voltage, mah stays the same. IE two 7.2v 1200mah becomes 14.4v and still 1200mah. More speed but not longer run time

    Parallel: doubles mah, voltage stays the same. IE two 7.2v 1200mah becomes 7.2v but 2400mah. More run time, same speed as one battery.
    T-maxx 3.3
    Rusty 2.5r
    Summit VXL
    Nitro 4-tec

  11. #11
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    mine is the one on the left... parralell... thats ok to run two lipo batteries right?

  12. #12
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Yes.
    That will give you longer run times.
    The LiPo's MUST be of the same cell count and should be the same mAh.
    Whatever it is I just typed... could be wrong.

  13. #13
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    so basically two of these should do the trick? SPC 2S 2500mAh 50C packs

  14. #14
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    and what would my run time be like with parralell?

  15. #15
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Run time with two 2500's in parallel... well over an hour, probably closer to an hour and a half.
    Whatever it is I just typed... could be wrong.

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    Well that sounds amazing... what kind of charger would i need and how long would they take to charge?

    Sorry about all these questions! You have been super helpful!!!

  17. #17
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    I always suggest getting a very good charger right off the bat. Some do not agree with me, but there are quite a few that regret not following similar advise. Buying multiple "cheap" chargers usually ends up being more expensive in the long run... especially if that charger is a cooker and ends up ruining your packs or worse yet like burning down your house.

    I recommend choosing something from the iCharger or Revolectrix line.
    I can help you through this process, but I will need some more information from you.

    Budget...
    The cheapest system out of the above would cost around $120-130. It would be around $150-$175 for the last setup you would probably ever need.

    With a even the cheapest charge system mentioned above you could charge both of these from LVC to full in about 20 minutes.

    My next post will cover some basic LiPo info.
    Last edited by JimmyNeutron; 01-28-2013 at 06:20 PM.
    Whatever it is I just typed... could be wrong.

  18. #18
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    I wrote this a while back... but most of it applies here too:

    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.
    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 warm... 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.


    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.

    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. They should be of the same brand as well as have the same amount of cycles on them.
    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... 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. Storage voltage is 3.85v/cell. 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. 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... I use a ParaBoard.



    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.

    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 typed... could be wrong.

  19. #19
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    Those links were helpful! There seem to be a lot of options.. which would you recomend?

  20. #20
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Either one of these:

    iCharger 106: $90ish
    TRX ParaBoard: $20ish
    Power supply $12+

    iCharger 206: $125ish
    TRX ParaBoard: $20ish
    Power supply $12+


    If you are going to stay with 5,000mAh or smaller batteries, the 106 will work just fine.
    If you might go to larger capacity than 5,000mAh, I suggest the 206.

    The 106 is 10 amps, the 206 is 20.
    Whatever it is I just typed... could be wrong.

  21. #21
    RC Racer
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    Ok... Links?

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  23. #23
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    Yea buddy!! thanks for that link mr newtron i just got all the stuff i need to finish my foam airboat drifter keeping the price under a hundred bucks using my existing trx electronics

  24. #24
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    if they dont have paraboards then where would you get one?

  25. #25
    RC Racer
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    oh i fount it, sorry
    still a little confused about the power supply

  26. #26
    RC Turnbuckle Jr. JimmyNeutron's Avatar
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    Have you checked your PM's, Warcara?
    Whatever it is I just typed... could be wrong.

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