Alarm when BMS protection takes battery offline?

[jaffadog]

I would like to implement an audible alarm when the BMS takes the battery offline. conceptually, this might be a normally-closed (NC) relay taking signal from B+ to P- and the relay output could switch an alarm that takes power from B+ to B- (or uses an independent power source). When the BMS trips, the relay would close and the alarm would sound. This of course is bypassing the BMS and drawing from the battery. so there is that known risk. not something you would leave unattended as the alarm could drain a battery that has undergone LVD.

I'm not an electrical engineer and don't quite know how to find and pick a suitable relay. the alarm would be a low power piezo (probably less than 100mA), so i suspect a low capacity solid state relay would be suitable. It would have to support NC wiring - not even sure such a thing exists with SSRs.

Any suggestions on components? Or is there a better way to do this?

 

[DW SD]

Chargery BMS has this feature and comes with piezo alarm hardware Did i see you on that thread?
And also flashes an LED when parameters are out of those established.

think you can also use the 87a side of a Bosch relay. One side 87 is NO and the other side 87a is NC.
if you use NC of Bosch relay when relay is de-energized it would close those contacts and signal the alarm.

As you know not all relays have NC wiring though.