Burning up motors... HELP

[Bkwoodz0593]

I recently purchased a turnigy 5.0 5000mah 2s 40-50c battery to run in my integy all metal scx10. After a couple runs with the new battery my motor starter smoking and I thought it was due to the actual weight of the crawler itself so I went to my lhs and bought a rc4wd 55t. After about 3 minutes I could smell burnt motor and quickly replaced with a dromida 2200mah 2s 20c and have had no problems since.

Are the motors burning up due to the discharge rate???
Only thing I can think of, but im a little confused because I did some research and found that alot of people use a 2s lipo with a 40-50c rating and seem to have no issues. Idk if they were running dual motors of if that would even matter, I just need to know what a safe discharge rating would be if that is my issue.

Sooner than later I'll convert to a dual motor setup with hobbywing quicrun 860 esc and dual 27t motors with 16T pinion and hotracing all metal tranny. What would be the best battery for this setup to obtain maximum run time without toasting motors??

 

[Sneetches]

Did you finish the rest of the 2200mAh without issues? Battery should have nothing to do with it in this case since you didn't change voltage, only added some grams of weight via capacity. Pull the spur/motor away from the spur and check that you can roll the truck freely without any binding. Also, avoid dual motors, that's a newb trap and adds no benefit over a single good brushed/brushless motor.

 

[Hardcoretam]

As above.
Remove the motor from the truck and with the trans still in place, roll the truck back and forward to make sure it rolls smoothly with next to no resistance.

What was the first motor you were using and what's your gearing you've been using?

Battery won't be causing the motor to smoke.
The motor only draws the amps it needs. If the battery can't deliver the amps then the battery will get hot quickly, rather than the motor.

 

[GLwagon]

current gear ratio?

Run-time comes from efficiency.
Brush motor will never have the power or efficiency of a cheep brush-less setup.

 

[CoolRunning]

C rating is simply the ability of the pack to sustain the voltage under load.

High C = lots of voltage hold compared to low C where the pack will sag and additionally get hot doing this.

Your high C rated lipo might be putting out 8.3V when fresh and maybe this is too much for the setup. I know my Axial 35T and 27T motors get hotter far quicker with a freshly charged high C rated lipo compared to a half discharged one.

 

[Hardcoretam]

I thought all freshly charged lipos would peak at the same voltage.

As far as i understand it, there is no difference between a higher C battery and a lower C unless you're using a set up that draws high current frequently. Although crawlers can draw a fair bit when stalling motors and in binds, it's not a constant high draw like a heavy E-maxx bashing or similar.

But i'm still fairly new to the Lipo world and happy to be corrected

 

[CoolRunning]

Both fresh low C and high C lipos will charge to similar levels and may even hold voltage to similar levels as there really isn't anything such as 60C anyway; there is no current draw 'standard' manufacturers go by (they make it up and simply compare their own batteries to each other) so this is just a reference to say this lipo is probably a better quality than a cheaper one but the difference might be marginal.

I believe a proper 30C that can handle 30C draws right through is possible from memory. That will suck down a lipo in a few minutes basically. You'll get about 30-50 cycles of that before that lipo goes off big time...maybe 25 from my experience (RC Helis are the gold standard of using up high C lipos in 3 minutes and as such kill them quick).

Basically the C figure gives you a little more confidence that the lipo may hold up better long term and deliver decently in a year compared to a cheaper, low C battery. Say in a perfect world 4.2v per cell so say 8.4 on 2S. Under load they will instantly put out lower voltage. An old, worn out pack may charge to say 4.16 per cell but under load will immediately drop much lower and as the chemical reactions cannot occur quickly, the voltage will just plummet and the battery will get hot trying to deliver what the system is asking for.

So yes, they are the same when new but a proper high C battery will continue to deliver the appropriate chemical reactions where the low quality battery will lose the ability to. Subsequently, it will sag immediately and puff and drop a cell and catch fire.

After a certain many cycles, even a great battery will sag. Lipos are reported to last only a few years even sitting on the shelf. You use them up and discard them before they become dangerous. I've had a 60C 5000 6S pack drop a cell at 50 cycles and it was so hot it burnt my hand when I (quickly) pulled it out of the heli (was a 12S system). A mate's heli burned up with $1000 worth of lipos (two 6S 5000 packs @ $500 per lipo). Probably had 70 cycles on it and the IR was ok.

IR is the most important thing for a lipo. Do you guys run electronic chargers that provide IR information?

For example, a great lipo has an IR per cell of say 2-3. A bad cell is say 15 and when you get into the 20's you better stop using the lipo. A battery with all cells in the high teens or low 20's in a time bomb.

 

[Hardcoretam]

I don't, but i have a multimetre.
Can i use the ohm setting to check them?

 

[CoolRunning]

I imagine you could use it though Googling might be the best option there. You're basically testing the resistance of the individual cell so you'd need to use the balance lead for that. Often one single cell is the weak cell and drops causing the lipo to sag harder and maybe like the OP hit LVC quick...this is a bad battery.

 

[SDheavymetal]

I don't, but i have a multimetre.
Can i use the ohm setting to check them?

NO- Harbor freight has some cheap DVM's.

 

[nightcrawler48]

LiPo and C rating. To determine what output you can get from your Lipo, covert your mah to actual amps, just divide the battery mah number by 1000. So 5000mah is actually 5 amps and 2200mah is 2.2 amps. Then the C rating comes in to play. In this case a 5000mah battery at 40C is capable of 200 amp (5 x 40) maximum sustained load. If you take the 2200mah battery and use the 20C rating, then it is only capable of 44 amp (2.2 x 20) maximum sustained load. So, for the 2200mah battery to have a similar maximum sustained output as the 5000mah, the C rating would need to be about 90C (2.2 x 90= 198 amps). If a LiPo shows a "Burst" rating on the label, the battery is capable of that output for a maximum 10 seconds. For the 5000mah 40-50C, if the 50C is the burst rating, then the battery is capable of 250 amps "burst" for a maximum of 10 seconds.

The other determining factors are the ESC amp rating and the motor amp rating. Most manufacturers of ESCs are pretty good about identifying the ESC amp rating. Motors usually take a little more digging to determine the maximum motor amp draw.

As mentioned, voltage for LiPos is constant (max 4.2V per cell fully charged, LVC usually between 3.2V and 3.6V per cell) no matter what the mah rating. The difference in this situation is the 5000mah at 40C battery is capable of 200 amp maintained output. Switching to the 2200mah at 20C reduces the maintained output to 44 amps. This is a significant reduction in the maintained amperage that could be supplied to the motor. Is it possible the motor is drawing its maximum amp rating continuously? That would generate some heat.

 

[EddieO]

Main reasons motors burn up.

A. bad gearing
B. Binding in drivetrain
C. Water/mud
D. Shitty cheap motor

C rate has little to do with them burning up, unless something else was already wrong...

And dual motors won't solve your problem....nor do they work like people think.

Later EddieO

 

[Hardcoretam]

Is it possible the motor is drawing its maximum amp rating continuously? That would generate some heat.

That's what i was thinking. Unless it's a very worn brushed motor or there's some serious binding somwhere the motor shouldn't be drawing that much amps.

If the smaller battery can't provide the amps the motor is requesting, will the battery become hot instead?

 

[mhowzit]

If the smaller battery can't provide the amps the motor is requesting, will the battery become hot instead?

Yes

 

[Bkwoodz0593]

Thanks for all the great info im gonna throw my turnigy pack in and see what happens!

 

[kbzx35]

Also check the battery plug and solder joint. Bad solder joints can create some serious resistance.

 

[mhowzit]

Also check the battery plug and solder joint. Bad solder joints can create some serious resistance.

Good thinking!