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Thread: LiPo questions

  1. #1
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    LiPo questions

    I'm finally going LiPo... but I need some suggestions. Here are my must-haves:
    1. 3s
    2. Compatible with trucks that take the 7 cell flat NiMH packs... so something that will fit the battery tray of, for example, the Slash 4x4.
    3. A fairly high mAh

    I've heard that SPC is the way to go when it comes to LiPos for trucks... but are they good enough for the Spartan? Is there a sweet spot for mAh when it comes to run-time VS price? Also, can anyone recommend a good charger? Preferably one that charges multiple batteries at once. I know there have been threads like this but I just couldn't find any that answer my questions.
    To the men and women of the US military, thank you

  2. #2
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    Gens ace are my choice of lipo. No puffing, low resistance and lots of power. Plus they are cheap. I run 2 of the 3s 5000 65-120C packs.

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    What does "Gens" stand for?

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    It's the name.
    The Super Derecho

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    Nice! Thanks. Any recommendation on chargers?
    To the men and women of the US military, thank you

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    I really like my iCharger 10B. Works great, had it for years. I think Proggressive RC sells them, they even have a bundle deal with the 350w power supply at a great price.

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    Quote Originally Posted by TraxxasTuesdays View Post
    Nice! Thanks. Any recommendation on chargers?
    I have been using a Hitec X4 charging station with a Green Power 350 watt (20 amp) power supply.

    The Hitec X4 will charge 4 batteries @ 5000 ma (5 amps) or any combination there of not to exceed a 20 amp max.

    The charger will operate remotely from your car or truck battery.

    I have been using this setup for two years now and has served me well....

    It takes a little over an hour to charge 4 ea 5000 mah batteries.
    "enjoy your ride"

    Dennis

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    I have another question. How do I know how much power I need to supply the charger? Say I have an 80 watt charger... how big of a power supply do I need?
    To the men and women of the US military, thank you

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    Ok I have a question.

    Bone stock spartan:

    Was running 2 x 5s 5000mah 35-70C packs in parallel giving me 10k mah for a total of 15 min run time or about 650mah/min mileage. total battery weight over 1300g. Avg motor temp 120-130 F

    5s packs broke, so just tried 3 x 2s 4000mah 40-80c packs in series (6s 4000mah) and now get 350mah/min Mileage. total battery weight just over 680g. Avg. Motor temp 90-105 F

    For those of you who told me my 1st set up was too heavy... you were right. I cut the weight by half and mileage doubled and hits its plane much quicker.

    MY PROBLEM now with the 3 pack x 2 cell combo is when I Nail the throttle it cuts out. Not 1-2 sec lipo cut off but quick cut outs like a car with a rev or mph limiter. It will briefly cut out regardless if I punch the last 10% of the throttle curve to top speed or the first 10% out of a turn. What do you guys think is causing it?

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    Not enough amps would be my guess.
    To the men and women of the US military, thank you

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    Quote Originally Posted by TraxxasTuesdays View Post
    I have another question. How do I know how much power I need to supply the charger? Say I have an 80 watt charger... how big of a power supply do I need?
    I'll try to state this as simply as I know... You have to have at least two of the following three: amps, volts and watts then the missing one can be calculated.

    In a fixed voltage situation to find watts the equation will be. watts divided by voltage = amps ( watts/volts).
    In your case you have a 80 watt charger at 12-14volts, so 80/12 = 6.66 amps so you would need at least a 7 amp charger.

    Hope this answeres your question...
    "enjoy your ride"

    Dennis

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    Ok. What if it can charge 4 batteries at 80 watts and 12v? Does that mean I need to multiply my 6.66 amp power supply by 4 and get a 27+ amp power supply?
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    Quote Originally Posted by jasonwipf View Post
    Ok I have a question.

    Bone stock spartan:


    MY PROBLEM now with the 3 pack x 2 cell combo is when I Nail the throttle it cuts out. Not 1-2 sec lipo cut off but quick cut outs like a car with a rev or mph limiter. It will briefly cut out regardless if I punch the last 10% of the throttle curve to top speed or the first 10% out of a turn. What do you guys think is causing it?
    My guess is that your 2s @ 4000 mah batteries are not equal in capacity. And or the series connection adaptors have too much resistance in them, the wire guage may be too small to handle the current required which in turn causes the voltage to drop very quickly then going into lipo cut off.

    What size wire is in the adaptor to connect the third battery. Is it one you made or purchased pre made?

    Quote Originally Posted by TraxxasTuesdays View Post
    Ok. What if it can charge 4 batteries at 80 watts and 12v? Does that mean I need to multiply my 6.66 amp power supply by 4 and get a 27+ amp power supply?
    That is correct.. Most power supplies deliver 12- 14v dc at a given wattage... In my case I have a 4 port charger and a 350 watt power supply which in turn gives me 25 amps of charging capability. I never charge more than 20 amps max at a time so as not to stress my power supply or charger.

    Example... 4 batteries at 5000 mah (5 amps) = 20 amps with 5 amps in reserve. If you have at least 20% head room in the power supply it does not over heat as easily and as it be known... heat is our enemy

    So you would most likely require a 30 to 35 amp power supply to be safe or just charge no more than 3 batts with a smaller power supply.
    Last edited by cooleocool; 10-29-2012 at 04:45 PM. Reason: post merge
    "enjoy your ride"

    Dennis

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    Ok thank you!
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    Quote Originally Posted by orca44 View Post
    My guess is that your 2s @ 4000 mah batteries are not equal in capacity. And or the series connection adaptors have too much resistance in them, the wire guage may be too small to handle the current required which in turn causes the voltage to drop very quickly then going into lipo cut off.

    What size wire is in the adaptor to connect the third battery. Is it one you made or purchased pre made?
    the plugs are XT60s and wire is 14g. I know allot of you guys would say 12-10g would be better but I've seen guys run 6s cars all day with 14g XT60 6s set ups and no problems. Then you think of house outlets and they are 14g running 2200watts for decades on end. this boat running about 1/3 of that. You think its the wires? If it were the lipo cut off i'd expect it to stop for a second or two while it reset, but this behaves like a bubble in a gas line (small choke or hesitation). I do see the logic of capacity but this happens thru out the battery cycle not at the end when it is dying.

  16. #16
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    House power is AC. Juss sayin.
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  17. #17
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    Quote Originally Posted by jasonwipf View Post
    the plugs are XT60s and wire is 14g. I know allot of you guys would say 12-10g would be better but I've seen guys run 6s cars all day with 14g XT60 6s set ups and no problems. Then you think of house outlets and they are 14g running 2200watts for decades on end. this boat running about 1/3 of that. You think its the wires? If it were the lipo cut off i'd expect it to stop for a second or two while it reset, but this behaves like a bubble in a gas line (small choke or hesitation). I do see the logic of capacity but this happens thru out the battery cycle not at the end when it is dying.
    2200 watts at 120 volts is just a little over 18 amps and on 14 guage solid conductor wire will work but is not acceptable, as NEC electrical code only allows 15 amp circuit breakers on 14 guage wire for residental use...
    The motor in your boat at full throttle is pulling in excess of 60 to 80 amps and on 14 guage wire you begin to turn the wire into an heating element. And as heat increases so does the resistance of the wire, which causes more heat to be generated.... a snow balling effect. 14 guage fine stranded copper wire will not handle that kind of current for any length of time.... Solder begins to melt at around 360 degrees F, so enough heat can be generated to melt/weaken our solder connections.

    Remember we also use alot more full throttle or close to, for a longer duration in our RC boats than with rc cars or trucks.

    Hope this clears the air a little.......
    "enjoy your ride"

    Dennis

  18. #18
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    all right i'll try upping the gauge ty

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    I turned off the Lipo cut off and all was fine. I did temp the wires and the 14g serieal was 94deg and from the series connector to the ESC 12g was 98deg. Opposite of what I expected. I Figure the 12g was hotter cuz it was closer to the ESC which was 114Deg. Actually aren't the stock motor wires also 14g?

  20. #20
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    The smaller gage wire should have been warmer. Not sure why you had higher temps on the 12g wire unless the soldered connectors are defective? Did you have the temp gun on the wire for each test?

    Yes the stock Castle 1420 1800 kv motor has 14 gage wire, and the wires on the speed control are 12g. At least they are on mine and it it one of the first upgraded motors and speed control over a year ago now.

    Don't know what just happened but when I added content it posted twice.. Oops
    Last edited by orca44; 11-10-2012 at 12:40 PM.
    "enjoy your ride"

    Dennis

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