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Hot battery and slow car

Hot battery and slow car

Old 01-12-2020, 03:47 PM
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Hi,
so recently my brushed 2wd Traxxas Rustler hasnít been going very fast. Itís probably going about 2/3 speed on a full charged battery. My battery is a 7cell NiMH 4500mah. The battery is getting really hot after running and one cell imparticular is getting very hot and even melted the plastic. I thought the problem was that there was too much pressure on the motor so I replaced the wheel bushings with bearings and I made sure the motor gear and reduction gear were not too close together. It still didnít fix the problem so I ran the car until it was completely discharged, let the battery cool and I am now charging it. I donít think this will work as I canít see how it would contribute to the battery overheating. Anyways, Thanks for reading and I hope you can help.
Cheers, Jamie
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Old 01-12-2020, 04:19 PM
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Good idea looking at the bushings and replacing them with bearings. If you remove the pinion gear and spin the rear wheels, does everything spin freely?

Also, when you check how tight the gear mesh between the pinion and the spur gears is. make sure you check all the way around the spur especially if things have heated up as it could have warped.

It could also just that your battery has a bad cell- in that case it would only be a new battery that would fix this problem.

Also, if you've got the optional pinion gear, make sure you are running the smaller gear!
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Old 01-12-2020, 05:01 PM
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Ok thanks for the reply.
The rear wheels spin freely, I checked to see if the spur gear had warped but it seems fine. I thought that it could be a bad cell so I might try replacing the one that gets really hot, I just plugged the dead battery in to charge and the indicator said the battery was fully charged within about a minute. Do you think itís possible the charger could be the problem?
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Old 01-12-2020, 05:36 PM
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If one cell is getting much hotter than the rest, the battery may be bad. If you have another batettery to try, that might help. If that is the problem, and funds allow and, maybe upgrade to Lipo.
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Old 01-12-2020, 07:37 PM
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I just replaced one of the cells with a new one. I charged the battery up and had a go, it went full speed at first which gave me confidence but it slowed down to a slower speed within a couple of minutes. I will charge it again and see if it goes better but if it turns out the battery is bad, I think I will invest in a quality lipo instead
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Old 01-12-2020, 10:18 PM
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sound like the motor brushes are about done.and those can not be replaced.. dyno motor and see what kinda amps its pulling..
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Old 01-12-2020, 10:38 PM
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Originally Posted by the rc guy View Post
sound like the motor brushes are about done.and those can not be replaced.. dyno motor and see what kinda amps its pulling..
A motor dyno isnít exactly a common thing for majority. Stock brushed motor is cheap enuff to just change.

Any chance could try another battery, a friends?
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Old 01-12-2020, 11:36 PM
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if you changed the bushings in the rear hubs, did you also change out the bearings in the transmission case. If those are still the plastic bushings they will have wear (and warping) that will suck all performance out of your motor/battery.

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Old 01-14-2020, 06:12 PM
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Your NiMH battery is probably the problem. I had one brand of NiMH that caused my problems that every time I let the pack sit for a couple of months, one cell would die. The charger thought everything was OK and it would show a voltage you'd expect while charging, but if I used a voltmeter afterwards, I'd see the total pack voltage was only around 8v, when it should have been over 9v.

You might have multiple bad cells. Might want to test voltages of every cell to see if they are similar.

Not uncommon for NiMH batteries to get really hot after running. The older they get the more internal resistance they develop. I'm sure you're not using your Rusty for a Sunday drive. Used to run a Rustler with a modified brushed motor and batteries would come out of it after a 5 min race too hot to handle.
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