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Hi. I’ve finally had some brain time to dedicate to the hobby and tried running my first RC10 build.

The car has parts from two very abused cars I bought online. Everything has been cleaned and rebuilt from the ground up.

So the car runs, but the battery is extremely hot after use. I read around,looking for a cause, and at first I thought it could be a crap battery, but the speed controller and motor also seem very hot to the touch after a while.
You can see the plastic wrapping on the battery has burnt through at one end.


So now I’m thinking maybe the gear ratio has something to do with it.


The car is powered as follows:

Motor: Trinity Green Machine 2 which I gather is a 27t stock motor. The motor has been cleaned and lubed.[att

ESC: Futaba MC112B

Battery: Generic,shop assembled,1800mAh nimh pack.

Gear ratio: 54t spur and 14t pinion, standard 6 gear transmission.


Any suggestions based on this setup?

I can get a 12t 32p Traxxas pinion here locally, but spur gears are not available.

Thanks,
Chris

how fast is it heating up? ie, how long are you running the car?

if you remove the motor, does the drivetrain feel free or does it feel like there is drag?

what surface are you running on?

the gear ratio does not look excessively wrong.

I didn't take precise note of how long I ran it, but no more than 5 minutes and then another 5 minutes after a short break. I'll run it again and time it this time.
But all I was doing was running it back and forth in a warehouse (concrete floor) to try it out. I did gun it back and forth quite a few times.

Before placing the motor in, the transmission was smooth and free. I could check again.

I'm doing all this on a very stringent budget. I could go out and get a decent battery pack which will set me back US$50 (I've checked prices), and compare. I probably will eventually, but wanted to make sure everything else is OK also.

I'm going to charge the pack up again to see how much charge I used last night.

Check that the gear mesh (pinion/spur) is not too tight.

Just finished charging the battery back up. It took 445 mAh. So I used about 1/4 of a 1800mAh pack trying it out last night, and the thing was hot! May have run it 5 minutes total come to think of it.

aakoskin wrote: ↑Fri Jan 10, 2020 1:36 pm Check that the gear mesh (pinion/spur) is not too tight.

It’s good. Checked. Thanks.

I’m going to try and measure the temp on the batt and esc. Don’t have a pirometer, but might be able to use the probe on my multimeter.

I just took a few temperature readings after running the car for a while on concrete and with the battery pack freshly charged. Charger cut off at 1887mha to be exact.

After about 3 minutes of running, everything felt fairly cool still: About 40C (104F) inside the battery, and close to 50C (122F) at the motor.
After 12 minutes of racing around it got pretty hot: almost 60C (104F) inside the battery pack, and 70C (150F) inside the motor.

I read a few comments on other forums where people mention these battery temperatures are actually quite normal; that 140F is about the limit for nimhs.

The run time seems OK. There was still some juice in the battery after the 12 minutes. That time would probably drop running on dirt or grass.

Ran it a little more and it died completely just before the 15 minute mark.

I've observed that brushed motors tend to build heat faster than brushless (especially if timing is greatly advanced) and nimh batteries tend to build heat as they discharge due to internal resistance. My lipos remain cool while the nimh batteries can become quite hot.
As such, I'll monitor temps and stop running the car when the motor becomes too hot to touch (perhaps 120-140 F). I like to adjust gearing so that I can achieve 10 minutes run time without overheating on brushless but it seems that 5 - 8 minutes is about the limit on brushed no matter how the car is geared. I'll seldom if ever go beyond 10 minutes per run.
Of course the kind of surface, track conditions, elevation changes, and how long you're at full throttle will affect temps.

Thanks Doug. Those are great reference numbers to go on.
This is my first electric and didn’t really know what to expect.

I will eventually try Lipo and brushless and 2.4GHz radio etc., but I wanted to try vintage electric first.

Now that i know things are within normal parameters, I can dedicate some time to tweaking and improving. I have a couple of motors and ESCs I’d like to try also.

Thanks again.