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  1. #1
    RC Competitor
    Join Date
    Nov 2015
    Location
    Dallas, TX
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    75

    My battery life is getting weird on my E-Revo VXL

    Ok so I have a 1/16 Revo VXL brushless.

    Factory pinion, and spur I believe is factory too.

    Twin Traxxas 2 cell LIPO's 2200's in parallel.
    Been using the Traxxas charger and balance charging them, of course.

    Back in Dallas I've been getting crazy long run times as expected... Probably 45+ mines.

    Now I brought my car to Denver Colorado and been driving through heavy snow... It struggles getting through it and for the most part I'm like 80-100% throttle going through it. My batteries will both die in 15-20 minutes TOPS!? ... Car goes in to LVC... slow blinking red...

    So I went to the hobby shop and bought 2 venom 1300mah 3 cell LIPO's... Connected them to the balance port on my Traxxas dual charger... Charged them up and took it for a spin... WAY faster as to be expected... (Both batteries in parallel)

    But the batteries died in 5 minutes?!

    The car went to LVC slow blinking red. There's NO WAY they died. So I took it home, charged them up again and took it for a spin... Same thing!

    There's no way that's right. Is the speed controller taking a crap, or am I charging my batteries wrong? Or is there something else going on?

    Any pointers here? I'm lost.

  2. #2
    RC Racer
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    Nov 2015
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    michigan
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    236
    Constant near full throttle will drop your run time,in dallas you probably didn't have that constant wheel spin.
    You dropped from 4400 mah to 2600mah with the venom so your run time will be about the same as a single 2200.
    I haven't experienced it myself but I have read that lipo doesn't like really cold weather.
    You got 15-20 min tops with 4400mah and then approx 5 minutes with 2600mah with less available amps and gobs of wheel spin in the cold,sounds about right.

  3. #3
    RC Competitor
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    Nov 2015
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    Dallas, TX
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    75
    Well I ended up taking off LIPO mode with the Venom batteries as soon as it hit LVC... just to try it out..
    I got 10 minutes more of run time at full power... Then I stopped because I didn't want to damage the batteries.

    Does this change your opinion about anything?
    Last edited by Xmaxximum; 01-12-2016 at 10:28 PM.

  4. #4
    RC Champion
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    Jun 2015
    Location
    Brossard, QC
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    1,211
    Check your battery voltage after it hits LVC.

    I did a good 20mins run with my MERV the other day, and my lipo cells were at 3.83v. I ran dual onyx 2000mah 2s. Temps outside was about 20F. I had constant wheel spin with the talons tires, but I wasn't constant full throttle.

  5. #5
    RC Champion
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    May 2002
    Location
    Midvale Utah
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    1,773
    Short answer, your car and batteries are fine, the issue is the cold.

    Long answer. When lipos are cold their internal resistance goes up, basically their C rating goes down, so your 35c battery willl act like a 20c battery, or worse. The colder it is outside, the worse it gets. If the batteries stay outside in the cold for a while before you use them, that makes it worse still.
    Basically what happens is that even though your batteries are not fully discharged, they are unable to supply the amps your motor is asking for, which causes the voltage to sag, triggering lvc.

    But, there is hope. The key is to keep your batteries warm until litteraly just before you use them. A pocket works well. Once you are using them, they will tend to create enough heat to keep warm, though running through snow might be an issue. When running in snow I would try to block off tye battery vents to keep snow out.
    Dacaur

  6. #6
    RC Champion
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    Jun 2015
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    Actually I ran mine in the snow and it seems the snow stays outside of the vent pretty well. I should have taken the batteries out when I hosed it down when done though.

  7. #7
    RC Competitor
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    Nov 2015
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    Quote Originally Posted by dacaur View Post
    Short answer, your car and batteries are fine, the issue is the cold.

    Long answer. When lipos are cold their internal resistance goes up, basically their C rating goes down, so your 35c battery willl act like a 20c battery, or worse. The colder it is outside, the worse it gets. If the batteries stay outside in the cold for a while before you use them, that makes it worse still.
    Basically what happens is that even though your batteries are not fully discharged, they are unable to supply the amps your motor is asking for, which causes the voltage to sag, triggering lvc.

    But, there is hope. The key is to keep your batteries warm until litteraly just before you use them. A pocket works well. Once you are using them, they will tend to create enough heat to keep warm, though running through snow might be an issue. When running in snow I would try to block off tye battery vents to keep snow out.
    Interesting.
    Thank you!!!!

  8. #8
    RC Qualifier
    Join Date
    Jan 2012
    Location
    Detroit, Mi
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    507
    Any battery in cold weather will have more resistance and less available amperage. Even a full size car battery will not have the same performance in 32 degree weather as it would have a 75 degrees. Same goes with lipo batteries. The battery has to work harder to give you the amperage you need to run your car's motor or starter motor in cold weather.
    ERBE, EMBE, big block MERV, Sl4sh

  9. #9
    RC Qualifier Fuglio's Avatar
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    Quote Originally Posted by jdavi519 View Post
    Any battery in cold weather will have more resistance and less available amperage. Even a full size car battery will not have the same performance in 32 degree weather as it would have a 75 degrees. Same goes with lipo batteries. The battery has to work harder to give you the amperage you need to run your car's motor or starter motor in cold weather.
    I know this is true, but im tring to learn more about electrical theory. What is the reason?

  10. #10
    RC Racer
    Join Date
    Sep 2015
    Location
    Quebec
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    118
    Here:

    Like most batteries, the temperature of a Li-Po has an impact on its performance. Consider that batteries rely on a chemical reaction in order to provide a current – a low temperature reduces the speed of this reaction and a reduction in overall pack performance may be observed on a cold day. Allowing a Li-Po pack to freeze is certainly not recommended, as this would almost certainly damage the pack.

    Taken from LINK

  11. #11
    RC Turnbuckle Jr. Squeegie's Avatar
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    Jun 2014
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    San Gabriel, California
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    Since you drove your rig in the snow in Denver, have you checked your bearings? Might be adding some load in your drive line...
    Creativity is intelligence having fun. -Einstein

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