hp 45/ power pack


I need help. I have an hp 45 and the battery pack shows
2.9 V. I recharge de pack, but won't charge more than 2.9.
I install the pack in the calculator and does not function.
The calculator functions fine with the electrical cord.
I think the battery pack has one defective cell, the middle
one and also the machine is malfunctioning, because 2.9 V
is enough to make the machine work.
Can some one give advise on this?



I think you're right. One of the cells in your battery pack has shorted. For some reason, the middle one is the most common one to do this (but I can't think of a good reason why this is so).
In any case, replace all 3 cells (it's not a good ide to mix old and new NiCds). Cut open the pack along the seam and take out
the old cell assembly. Tear of the contact strips that connect to the springs in the calculator -- you need these to connect up the new cells.
Tek 3 AA size NiCd cells, with solder tags and wire them in series like the original cells. Solder the ends to the contact strips that you recovered from the old cells. I am pretty sure that the contact strip neares the front edge of the calculator when the pack is installed is +ve.
Put them back into the pack and glue the housing together (use Plastic Weld (dichloromethane) for this).
Ooops... 'Tek' should read 'Take' -- my web browser doesn't really allow editing.

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