HP 41C replacing nicads / corroded contacts



#2

I have several rechargeable battery packs both for the calculator, printer and tape drive which I would like to rebuild. Which nicads are best suited for this purpose for the calculator(looks like 1/3AAA) and the printer(?C cell).

I also have a 41CV with one corroded contact closest to the charging lug. Is this a major undertaking to repair or as we say "a piece of piss"? :-)


#3

1/3 AAA are a littel smaller than the original cells, 1/3 AA are a little too large, but you might be able to squeze them in if you were prepares to do a little work on the battery pack.

The problem with the 1/3 AAA is that they are probably a little lower in capacity than the originals, so the charge current is even more excessive. It just means that you don't leave it on charge for too long. (as for how long, you can measure that with a thermometer)

The larger packs use sub-C size nicads. These are readily available and are now of significantly higher capacity than the ones originally used.

The battery terminal is not too hard to repair if it's not too badly corroded. There are several guides on how to do this floating around. It's apparantly not too hard. I've not had to do it, so I can't offer advice.

#4

I have rebuilt 2 battery packs for the printer. I used rechargeables from Radio Shack and had good results. One thing, the original cardboard wrapping around the old cells will fit very tightly if at all. I wrapped my batteries with black electrical tape with good results. Just pay attention to polarity and you should be OK. I hope this helps.


#5

Be certain to use the replace-a-cell batteries from Radio Shack with the solder lugs already attached. It is not easy to get the batteries soldered together without them.

#6

The contact is not very hard to fix, I have used a small piece of copper sheet to fix a few, unfortunately I had to buy a roll that is 12"x30" where I needed say 1/4"x 3/8" or so! Fortunately, I have the bulk of this stuff left over, so should you or anyone else need a small piece email me and for like I have told others; for the exhorbitant price of a picturesque postcard from your part of the planet it's yours at no additional cost! Long live vintage hp's and thanks again to Dave H. for the site!

#7

As I recall, the correct size for the 41's NiCd pack is a 3/4 (75%) N-size cell, which is usually fairly obvious in a cell's part number (as "750N" or something similar), if you try to order them from a catalog.

Hopefully this might be of some help to you.

Best, aaron www.zianet.com/goodman


#8

1/3 AAA may be easier to source, but are slightly smaller. The capacity is close to the originals.

1/3 AA are slightly larger and possibly could be made to fit with some effort (I havn't tried). 1/3 AA have trice the capacity of 1/3 AAA hence a desire on my part to try to make them fit :-)


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