battery education sought

Allison ajp166 at
Sun Oct 16 15:53:11 CDT 2005

>Subject: battery education sought
>   From: "Jay West" <jwest at>
>   Date: Sun, 16 Oct 2005 13:30:35 -0500
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at>
>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.

Extinct due to envromental concerns.  Common use these days are the 
3V lithium coin cells for the same uses.

>Are mercury batteries rechargable? I would have thought they'd use a nicad 
>or something to charge up while the unit was on.

Do not attempt to charge.  Bad things can happen.

Mercury batteries were used for many reasons, high energy density, 
extremely long shelf life at near zero power consumption and very 
stable voltage over life.  Lithium cells have replaced them in 
most apps where battey drain is low and extremely long stable 
life is desired.

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

I'd expect that would work just fine.  If your really uncertain add a shotkey
rectifer in series (Vf about .3V).  My bet is the logic they keep alive
is a CMOS RAM and in operation that device Vcc is 5V.


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