s2740vc does not work on 6s lipo

[CarlOlsson]

My task was to test the s2740vc on 24 volts.

• Erased flash
• Flashed the bootloader from 68e34de6_gcc4_8_4_Ben
• Flashed the fw from 68e34de6_gcc4_8_4_Ben

Connected a 12v power supply and spun the motor, no problems.

Connected 24v battery, after approx. 2 seconds there was a spark and smoke. A resistor came off and now there is a short circuit between the ground and power connection.

The setup:

ESC after spark

Of course I should have used a current limiting power supply if I had one. We do have a fuse but did not consider it since well, I forgot it and I really thought that just voltage without spinning the motor wouldn't destroy it

[LorenzMeier]

@bendyer Is this a firmware related issue or something for real?

[bendyer]

@CarlOlsson I notice you had a JTAG adapter attached—was there an active debug connection, and were any breakpoints set? Also, what motor was that? From the two-second delay it sounds like the failure occurred as the motor resistance and inductance test was starting.

@LorenzMeier I don't think it could be firmware if the device wasn't re-flashed between 12 V operation and 24 V operation. I have just re-run two units on 25 V, and they work fine, but then you'd expect a component rating/marginal component issue to exhibit board-to-board variation (and it's notable that this is a different failure mode to the other board).

I'll test my remaining units at the full 27 V to see if they exhibit the same problem.

[CarlOlsson]

Hi Ben,

• No there was no active debug connection, it was still connected since I just flashed the bootloader.
• The motor is the same one we have been using since we started testing, the Hacker-A40-14.
• No fw was changed between 12 V and 24 V operation, I just unplugged the power supply and connected the battery

[LorenzMeier]

Potentially related to the braking on #18.