HP41CX, corrosion on (-) of one battery

[Uli]

I am also using rechargeable batteries. I have three hp41cx with these batteries.
Only one calculator has this issue.
I can't see any damages at these batteries.

The batteries are named as followed:
BlackFox
Ni--MH
BF-500N-Ni-MH-1.2V-500mAh

Maybe one of the four contacts in the calculator is not as good as the other three ones. But there is no different to see. There is no corrosion inside of the calculator. There was no battery leakage inside of the calculator.

I have had installed four modules.
CCD, math1, x memory, hp-41 advantage.
That is the only different to the other 41cx I have.

Now I make a test over the next couple of days without modules.