Low SOC and Lynx Smart BMS ATC = NO

Q&A and troubleshooting
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1

Hi

I have a new system and after having the BMS swapped under warranty I thought it was all working. I have multiplus 2, lynx smart BMS and NG Lifepo4.

The batteries have drained to 10% soc. I switched the inverter to charger however the BMS say ATC = no. What do I need to do to get the BMS to say ATC = yes as I assume this is the problem.

Thanks

2

Make sure that the batteries are warm enough, the charge threshold is 2degC to stop charging and 3degC to restart charging. A high cell voltage or temperature is the only other reason you should have ATC disabled.

3

Thanks. If SOC drops below the discharge floor will that prevent the BMS enabling charging?

Does the charger have to present a certain voltage on the right hand side of the BMS before it will enable charging? I think I observed from Victron connect that the voltage was less than 13v but I’ll need to check next time I do this test cycle.

4

Text below is taken from the manual. All of the conditions to close the contactor after low cell voltage or low SOC are OR conditions. I was using the app but the BMS declined to close the contactor.

This is the normal operating mode. All interfaces are operational, and the contactor is closed. If the Lynx Smart BMS was off due to low cell voltage or low SoC shutdown, it will exit OFF mode and return to ON mode when

  • it detects a charging voltage >11.7V (>23.4V for a 24V system or >46.8V for a 48V system) than the battery voltage on the system side or

  • when all cell voltages are higher than 3.2 V in case of a low cell voltage shutdown or

  • when all cell voltages are higher than 3.37V in case of a low SoC shutdown or

  • when it is turned back on via the Remote on/off switch or

  • when it is turned back on via the VictronConnect app.