Cell #1 low voltage inverter shutdown

[David Cashin]

Only recently we've noticed the inverter getting remotely shut down by the SBMS during high load (for us that is a kettle). Then a few moments later the inverter turns back on again. This cycle may repeat a few times under load.

The system is around 80-90 % SOC

Upon investigation, with load, cell #1 is dropping to around 2.8 volts (which is the default low voltage cutoff). 2 or 3 other cells drop to about 3 volts under load. Cell #8 stays the highest.

We do not have spec sheets for these cells so I do not know the original C rate. However, the cells used to be able to handle these loads.

My assumption is the cell health has deteriorated and has reached end of life. Does it make sense to try to replace just cell 1? Or will that throw off the balance of our 8-cell system

Thanks,

[Dacian Todea (electrodacus)]

David,

The more likely scenario is that there is bad contact at the cell's terminals.  A photo of the cells and one or two of the SBMS0 showing the cell voltages with no load and then under load will be helpful.

Not sure what is the kettle rated power but I will suspect somewhere in the 1500 to 2000W range that will be at most 80A and no cells should sag to 2.8V under such a load not even small 100Ah cells.