BMS high voltage alarm

Hello,

I have a system recently installed using third party Lithium battery with BMS accepted by CAN connection on Cerbo GX. The systetm is configured on ESS.

It turns out that system send an alarm from the BMS instance with high voltage alarm (the limit is 57V) but the solar charger shows only 55.6V.

However on MPPT detailed history shows on battery a max value of 59.82V. We have three batteries of 104Ah 51.2V in parallel, two Multiplus 5kW and 100A 150V MPPT solar charger. The alarm comes from battery BMS. Absorption and float charge parameters in solar charger are 58.4V suggested by manufacturer.

This alarm only appears when batteries are 100% SOC. We don’t know why batteries get a max value of 59.82V if solar charger paramteres are lower than this value.

Any help will be appreciatted.

When my BYD battery reaches 100% SoC, it also sends out an Overvoltage Warning (not Error), even though Max Voltage etc is regulated by the BYD Control Box.
I’ve decided I’m simply going to ignore this warning.

Hello @dgmar_ni ….some lithium batteries with internal BMS can go into a mode that “protects” the battery by disconnecting it when they are fully charged. It may signify to the CerboGX via the BMS.Can port that the battery is full and may signify an error as the battery goes into “protection mode”. When it open circuits it may allow the charger to spike a little before settling back done providing that higher than usual terminal voltage reading.

This protection mode is normally transparent to the user as when load is applied the battery is enabled immediately.

I don’t know what batteries you are using but I am just presenting a plausible story that may be the reason for the behaviour you are seeing.

Hello @Yachtbird thank you for your response. It wouldn’t be a problem if the alarm only is only a warning but sometimes the system completely shuts down specifically when inverters recharge batteries.

I was thinking in two ways: ignoring the alarm can be one but I am not sure if this can be done on settings and then alarm rules and second way is both chargers either solar or inverter just get to 98% or 99% and then stop charging but I am not sure if adjusting the charging parameters will do it.

Again any help will be appreciated.

There’s a whole section written about the BYD high voltage warnings in the BYD / Victron manual. Perhaps have a look there…

https://www.victronenergy.com/live/battery_compatibility:byd_b-box#high_voltage_warning_or_alarm_shown_on_battery_status