In order to avoid opening my pelican case (which contains Battery + RX + VESC + messy dielectric oil), I would like to charge my battery through the motor connector.
In theory it should work. I could use any pair of the 3 motor connectors and the current would pass through the Mosfet flyback diode and reach the battery. The loss with a 5A charge current should be 2 * Vf * I = 2 * 0.6V * 5A = 6 Watts. The Mosfet + aluheat sink (+ oil in my case) should easily handle this. I’ll also endup with 1.2V less on my battery than what the charger is sending. But I don’t really care.
The even better option would be for the ESC to activate specific Mosfet so I could charge without going through the diode. But I think that even without that, it should work without problems.
I could not find anyone having tried that? What could go wrong ?
If the VESC does decide to turn the FETs on, you will short-circuit your charger or have reverse polarity…
As far as I know the VESC does some internal calibration at startup and measure some values, I assume it powers the motor shortly, therefore switching some FETs
I can also hear a short “chirp” from my motor at VESC startup
You can probably set the VESC to some openloop mode where it closes 2 FETs correctly. However, it cannot turn on the FETs 100% of the time due to electrical restrictions, which will probably annoy your charger
Amazing idea what they are doing with the boost charging using the motor windings! Even though it’s not exactly what I want to do, it’s a nice feature!
If the VESC does decide to turn the FETs on, you will short-circuit your charger or have reverse polarity…
Right… I need to power on the VESC, then wait a bit before plugging the charger.
However, it cannot turn on the FETs 100% of the time due to electrical restrictions, which will probably annoy your charger
Yep, that will result in 1.2V jumps when VESC opens the FETs. And I would need to tell reconfigure VESC via BLE before each charge. For a first try I think I’ll just go through the diode with low amps and see how it goes.
A side question - why did you decided to fill with dialectric oil instead of say potting compound?
Does it help to dissipate heat from the ESC?
Do you still expose ESC heatsink to outside?
Thanks
No, I did not want to cut a hole (and seal) to expose heatsink outside. So my plan was to use the thermal mass (4kg of metal takes lot of energy to be heated) of the battery to “store” the heat generated from the ESC. I just needed a way to thermally couple them together and the oil is perfect for that.
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