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  1. #1
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    Just got 2S Lipos, I'm unimpressed, question about 3S

    2S just doesn't have the relatively explosive power of the stock pack ( 8.4V lipo peak compared to ~10V stock battery peak). I'm thinking of going 3S for bashing but I don't want fans hanging off the motor and speed control so I got to thinking.

    What If I chose the 70/30 setting on the transmitter and glued some sort of throttle travel limiter to the transmitter ( behind the trigger) so that I would not be able to apply full throttle. This way I would get more punch than a 2S while not fully utilizing the 11.1V ( or 12.8v peak) of the 3S lipo.

    Is my thinking correct on this? Would this be easier on the ESC and motor relative to unrestricted throttle?
    Last edited by skadebo; 05-05-2010 at 08:28 AM.

  2. #2
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    You'd be restricting your WOT, but I'm pretty sure that all these ESC's use PWM (Pulse Width Modulation). It oscillates rapidly between 100% throttle and 0% throttle to go at whatever input value you give it.

    What this means to you is that when you put your finger at the 50% mark, the ESC is switching 100% on half the time, and completely off (0%) half the time. If you put your finger at 20%, that means the ESC is running 100% on for 1/5 of the time, and 0% on (fully off) for 4/5 of the time. This happens very, very rapidly so that you don't notice the pulsing. You do end up exposing all those components to the higher voltages and power levels (wattages) associated with 3s.

    I can't say that restricting your maximum throttle position won't reduce temps on 3s, but I can say that I doubt it will have the full impact you're looking for.

    Have you tried simply gearing up? Your (decent) LiPo should give you some headroom for that.
    Last edited by jesusthepirate; 05-05-2010 at 08:56 AM. Reason: Clarity, Politeness.

  3. #3
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    I have never ran 2s LiPO's but they should have much more punch than a NiMH, The 1st time I started with LiPO's, I accidentally put my truck in training mode, might want to check that, The LiPO pack should have a lot more punch (can deliver alot more AMPS) with a bit less top speed(lower tops speed)

    try resetting the ESC and recalibrating your controller, and make sure Training mode is off

  4. #4
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    also the radio con be programed with a throttle limit.

  5. #5
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    I'll double check my transmitter and ESC settings. The only thing I changed was enabling of the LVC on the ESC by holding the power button for ten seconds after which the motor beeped musically to indicate LVC turning on.

    The pack didn't accelerate as violently as the stock pack and top speed was slower as well. Obviously it held it's power for way longer and more consistently, as is typical of a lipo, so that was good.

    @jesustp: I understand now and I'm pretty sure you're correct. I would be restricting WOT as you said. I think my method out and see what happens. Worse comes to worst, I'll put a fan on the ESC/motor.

    Also, I'm using relatively cheapy ******* lipos, the ones rated at 30C, for all that's worth. This could be my problem.

  6. #6
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    ******* LiPos work great, and even 2s will pack a lot more punch than the stock 7-cell NiMh. There has to be something else wrong.
    I need R/Cers anonymous.

  7. #7
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    Quote Originally Posted by RobWilJas
    ******* LiPos work great, and even 2s will pack a lot more punch than the stock 7-cell NiMh. There has to be something else wrong.
    Agreed. I was ready to ask if he was running WinForce, which is reported to feel pretty bad... but ******* 30C should certainly be fine, assuming it's 4Ah or more.

    @ skadebo - maybe you just got a dud pack. Did you order more than one? If your EPAs and calibration are all fine (I don't see why they wouldn't be, if they still work for the NiMH pack) I think the next step would be to find someone local to loan you a pack for testing, or test your pack in their truck. Which is often easier said than done, I know.

  8. #8
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    Yeah I ordered two! I'll test out the other one tonight. They're both the 5200mAh models. They both peaked just fine and both were balanced to perfection.

    Edit: Do lipos need break-in or cycling like nimh/nicd?

  9. #9
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    Quote Originally Posted by skadebo
    2S just doesn't have the relatively explosive power of the stock pack ( 8.4V lipo peak compared to ~10V stock battery peak). I'm thinking of going 3S for bashing but I don't want fans hanging off the motor and speed control so I got to thinking.

    What If I chose the 70/30 setting on the transmitter and glued some sort of throttle travel limiter to the transmitter ( behind the trigger) so that I would not be able to apply full throttle. This way I would get more punch than a 2S while not fully utilizing the 11.1V ( or 12.8v peak) of the 3S lipo.

    Is my thinking correct on this? Would this be easier on the ESC and motor relative to unrestricted throttle?

    I've Found 2s batery's are close to comparable to the Stk Bat but last considerably longer.

    As for 3s , stk pinion, we get away with back yard or stret running OK no overheat. Where it has ben a problem though is Tight track racing & especially Gravel, Sand pit running, the extra load sems to bring the temps up.

    Al
    MMM/2650, E-maxx Body=FUN !
    3 Slash 4x4
    Pede 4x4

  10. #10
    RC Racer
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    Quote Originally Posted by akesj1
    I've Found 2s batery's are close to comparable to the Stk Bat but last considerably longer.

    As for 3s , stk pinion, we get away with back yard or stret running OK no overheat. Where it has ben a problem though is Tight track racing & especially Gravel, Sand pit running, the extra load sems to bring the temps up.

    Al
    I agree, In the last week I have had 4 new battery packs.

    4200mah Nimh
    5000 40c 2s Lipo
    5000mah nimh
    4000 20 3s lipo

    That is ranked in order of outright 'punch' the 3s is crazy easily double or more of the 5000mah Nimh. The 2s lipos are nothing special really, just longer run times with consistent power from start to finish.

  11. #11
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    [QUOTE=skadebo]What If I chose the 70/30 setting on the transmitter and glued some sort of throttle travel limiter to the transmitter ( behind the trigger) so that I would not be able to apply full throttle. This way I would get more punch than a 2S while not fully utilizing the 11.1V ( or 12.8v peak) of the 3S lipo. QUOTE]


    Hmm, this is a very interesting idea...
    Darn you, skadebo, you have me wanting 3s again!!
    PLEASE do not PM me and immediately go offline :p

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