search

luna-cycle / vesc_bms_fw

The VESC BMS Firmware
GNU General Public License v3.0
0 stars 0 forks source link

Long term overvoltage / IC over temp #4

Open diegosarli opened 2 years ago

diegosarli commented 2 years ago

I run test leaving the pack connected to a power supply (59V) to fully charge the battery and evaluate the Overvoltage behaviour.

Starting with the pack at 90% charge, after 2.5 hours charging all the cells seems to converge to 4.2V while charging and to 4.15 when the charge is interrupted by the bms. image

The charging process start with charge - interrupt cycle about 3 sec charging 10 sec balancing. the more charged the battery is, the longer it stays balancing, after 2 hours of charging-balancing the balancing periods are about 10 min, whit only a few sec of charging. After 2.5 hours the pack is permanently disconnected and tying to balance. I assume that the charger will stop the charging process when the current goes below some threshold, and keep the pack in "floating" state.

I was concern about this condition but seems that is not going to be an issue.

The issue that i notice is related with the AFE temp, at this charge state (97%) even if i configure 1 balance channel the IC temp rise to 75°C, the temp protection work ok and the balance process is stopped.

But I think that we need some how improve the IC dissipation.

The pre regulator stabilized about 67°C, the mcu was awake during all the test.

image

diegosarli commented 2 years ago

How about mounting a heatsink on the AFE? something like this: https://www.digikey.com/en/products/detail/assmann-wsw-components/V5618A/3511413

nitrousnrg commented 2 years ago

How about mounting a heatsink on the AFE? something like this: https://www.digikey.com/en/products/detail/assmann-wsw-components/V5618A/3511413

I think most of the heat dissipated in the AFE comes from the built-in linear regulator. If that's the case the most effective way to manage the temperature is by reducing the current draw, 1/2 the current produces 1/4 of power draw. Maybe the MCU code runs harder while balancing?

diegosarli commented 2 years ago

During balancing the mcu runs normaly, only a few lines more.

The AFE internal regulator is after the board pre regulator? In the new hardware we can lower the pre regulator output voltage?