PRS-950 (and others): Battery replacement ever done by yourself? Result?

Hello all,

I have a nearly 10 years old PRS-950 and did a battery replacement by myself. Basically this worked and I was able to use the reader with the replacment battery to read.

But the new battery cannot be loaded - no symbol on the display for load, no red LED, nothing. When trying to load via computer I always get the error 'Charging stopped', 'The reader is currently experiencing extremely temperature...'

I thought that the battery is maybe bad and bought another one (different
trade) but it is the same with that, exactly the same behavior, exact the same error message. Whatever I tried, what devices, computers, ... I used: still the same.

Is there someone who also tried to do this replacement on PRS-950 or another PRS- and had the same issue? Or even not?
Is there maybe a check / a blocker built in the device which prohibits the usage of non Sony batterys in it?

I really appreciate every answer. With searching in the forums I was not successful finding any thread regarding this subject...

Thank in advance, Franz Peter.