I have a situation that may or may not be unique, so here goes:
The setup: I have a battery bank of 20 LiFePO4 batteries, charged by 6, 420 watt solar panels feeding a 100 amp MPPT charge controller. The panels are mounted in an array that tracks the Sun in 2 axis, and is controlled by an Arduino Mega. The Mega is fed with a power supply that can take from 8 to 40 volts and step it down to 5 volts. There is also a 6KW inverter connected to the batteries.
The problem: As long as the batteries are charging, everything is fine. The problem arises when the last battery's BMS shuts off, and the charge controller is now powering an open circuit, and the voltage spikes high enough to reset/damage? the arduino power supply, and trips the inverter's overvoltage alarm. It only lasts a few milliseconds before the charge controller shuts it off, but the damage is done, and everything has to be reset.
Solutions tried: I added this TVS diode across the battery leads from the charge controller, and now the arduino works fine, but it still exceeds 32 volts and thus trips the inverter overvoltage shutdown/alarm. BTW, Tech support for the controller is useless. I speak Chinese about as well as I do Aramaic. I'm on my own, apparently. LOL
Two weeks ago, I had never heard of a TVS diode, and thought that a diode with a breakdown voltage of ~31 volts would work. Wrong. Digging into the data sheet, I see that 31.28 is the MINIMUM breakdown voltage, while the max is over 34 volts. A diode with the maximum BD voltage below 32 volts puts the standoff voltage less than the highest battery bank voltage of ~29 volts, and the last thing I want is to create a situation where there is essentially a dead short across the battery bank and it's 2000 amps.
I hate to reinvent the wheel here, so am open to suggestions from folks more knowledgeable than I (almost everyone here, I suspect).
Sorry for the long post, and as always, if the mods feel this is in the wrong section, please move it. A hearty thank you to anyone who has read this far!