4S- Li- Ion SOTA battery

This battery consists of recycled Li-Ion cells type 18650.

Time and again, we have to deal with defective Li-Ion batteries in the repair café next door where I’m working in. Usually individual cells became defective or the battery management unit is broken. The (remaining) cells are sometimes still as good as new (i.e. close to their original capacity) – too good to throw away!

10V reference voltage source

The work with lithium cells called for voltages to be measured with an accuracy of at least 50 mV, for instance to prevent overcharging of the cells.
Over the years, a number of multimeters have accumulated in my shack – with quite different quality. Now the question was: which meter should I trust? For some of the devices, not even information about their accuracy was available any more.