Jim S wrote:

I have a battery tester, but am coming to the conclusion that it might give
wonky readings with rechargables.

My DECT handsets own chargers and my Speed8 (Ansmann not Bentley!)
charger seem to disagree about what constitutes charged.

After about a year the phones seem to get to a point where they don't
hold much charge, so I remove the AAA NiMH cells, and charge them
externally, until the (delta-V) charger shows them as full, then I leave
them on trickle for a while. When I put them back into the phones, they
show zero bars of charge and then spend the next few hours recharging up
to 3 bars, almost as though the bars are nothing to do with reality.