battery education sought

[Tony Duell]

> 
> I noticed my HP 262X terminals have a "Duracell TR133" battery in the back 
> to maintain settings when powered off. The battery indicates "Mercury" on 
> the side.
> 
> Are mercury batteries rechargable? I would have thought they'd use a nicad 
> or something to charge up while the unit was on.

No they are not. 

IIRC, it lasts a good few years, but was designed to be 
customer-replacable (hence the little plastic clip-in holder). A NiCd 
would probanly have been soldered to one of the PCBs.

> 
> The TR133 battery also indicates "4.2V". It seems the Duracell replacement 
> for this battery is Alkaline, and 4.5V. Should I use it?

IIRC, a PX21 Alkaline battery is much the same size (and 4.5V) and works 
fine. Same battery as used in the EDC Praktica SLR cameras, BTW.

-tony