Weird 42S battery problem

[Geoff Quickfall]

so normally the batteries drain uniformally.

Which battery drained starting with 1 (+ve-ve), 2 (+ve-ve), 3 (+ve-ve).

Was it 1, 2 or 3 or was it random, that is 1 and 3 or 1 and 2...?

If it was consistent, both 3, then for some reason the battery at position three is shorting independent of the other two and the on/off switch. Suggests that the contact tab is bridging the +ve and -ve components of the battery at the -ve end of battery 3.

I cannot see anything internally causing a drain of one cell independent of the other two unless:

-as stated above.

-two defective batteries.

Especially with the two remaining cells tested at 1.55 volts. Your battery tester, does it test under load or just voltage?

Geoff