Why are my batteries getting hot?
 

My son has a BL Rustler. Using the MM5700. He runs Tenergy 7-cell NiMh packs. I can't say right off the top of my head what the gearing is, but when I put the MM in it, I used the recommended gearing from others running the same setup.

For months now, it has run great. Never gotten hot. Never thermalled. Now just this weekend, he has melted the shrink off of three battery packs in a row with the ESC being warmer than usual and the motor being very warm. . . I wouldn't say hot just yet.

Tranny feels as smooth as it ever was. Mesh hasn't changed.

What else should I be looking for?

better batts, your nimhs could be on there way out..... look for any loose connections or breaks in wiring.. check to see if your motor spins freely

I know better batteries make a difference. I let him run my LiPo's when I'm bashing with him, but for an inexpensive battery, I can buy him a box full of the Tenergy packs, let him run them and charge them, and never worry about a LiPo fault or loss of an expensive battery.

I'll pull the pinion and make sure the motor spins freely.

All wiring and connections have been double checked - we use deans exclusively.

What would the effect be of a steering servo going south? He only has a 2055 Traxxas servo. If it starts to go and draws excessive current from the system, would battery voltage drop substantially enough to overheat?

I can't imagine a servo dying would cause it. I'd put another vote on the battery not holding up any longer. Hmm but if that were the case you'd think it would be gradual.

Have any settings been changed on the ESC? perhaps reset it to stock (and upgrade to latest firmware if you havent). Maybe an accidental radio program (could be very hard to do... how young is your son? :P) could have set the timing high or something? Or could he have taken the initiative to gear it up himself? Or maybe he's just driving it harder?

All long shots I know, or possibly obvious things to think about (depending who you talk to), no harm in bringing them up though I guess...

Afterwards see if the vehicle moves freely as well. Check all possible areas for binding. Double check the plugs on motor and ESC.

Tenergy batteries are not very good cells to begin with. I had a pack once and it was pretty much junk. If you want to run NiMH get some better quality cells like GP or IB cells and you will see better results.

Did you check the wheel bearings? Are the wheel nuts too tight? I've done the latter without noticing.

Your nuts were too tight? I can see how that would cause some binding...

My vote is for poor batts > heat. Some people have luck with tenergy, the majority dont by all accounts.

I used to run nimhs (puke packs) go lipo bro!

Hey- some WD40 and a couple left-hand turns with my nut driver and I'm bind-free! :rofl:

After checking things out thoroughly today:

1.) He is due for new wheel bearings. They are not smooth, but they are not shot, either.

2.) Unable to locate any physical drags, I plugged the MM into the 'puter and it came up with a setup error. It said Punch Control Out of Range. ??!!?? I don't understand how that could be. I'm the ONLY one that has the ability to plug the MM in and change settings and I doubt if it would be possible to get the Punch Control out of range by just fooling around with the ESC.

Anyway, after resetting the parameters, he ran two Tenergy packs today without any heat issues.

Thanks for the help!!

Interesting. So the punch control being all out of whack was the culprit then? I don't think you can set the punch control to more than 100% to begin with anyway. Definitely odd!

I wonder if you have a defective unit (in that it has the ability to apparently reset certain parameters way out of normal range...).:gasp:

Anyways, like some others said, I would also keep an eye on those NiMH packs. I've had IB4200s (notorious for having a short life span but great performance) poop out rather suddenly (not as gradual of a performance degradation as you may think, or that I thought I'd experience).

Gremlins... :yes:

Count yourself lucky on the tenergy's - the 7cell 4200s I bought were the worst packs I've ever had. They might make some good packs, but something about their consistency is whacko- few get decent useable packs, most get near worthless packs that way fail to live up to rating and die after a short lifespan.

I am aware of the crap battery packs that are run in the truck. But, as stated, I buy them six or more at a time, hand them to the kids, and let them beat the snot out of them. If they burn them up, I am not out any $$$. When I bash with the kids, I let them run my LiPos.

I have three boys, ages 5, 10, and 15. They all have electric stadium trucks. The older boys have rusty's with MM5700's and the youngest has a stock Raven (picked it up CHEAP, slightly used). Supplying them all with decent LiPo packs and crossing my fingers that they don't abuse them would be silly.