Rebuilding an HP 41 battery pack - Printable Version +- HP Forums (https://archived.hpcalc.org/museumforum) +-- Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum-1.html) +--- Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum-2.html) +--- Thread: Rebuilding an HP 41 battery pack (/thread-165994.html) |
Rebuilding an HP 41 battery pack - DavidShenk - 04-18-2010 I am in the process of rebuilding a 82120A battery pack for my 41CX with new NiCd cells. The problem I'm having is that the old cells leaked and damaged the metal contacts that mate with the calculator. They are both broken and I don't think they can be used again. Does anyone have an ideas for a substitute for those metal contacts? My guess is they have to have some spring or flex in them so the battery pack can be removed, but maintain contact otherwise.
Dave
Re: Rebuilding an HP 41 battery pack - aj04062 - 04-19-2010 what about trying foam with a plate, like in all the 48 series?
Re: Rebuilding an HP 41 battery pack - DavidShenk - 04-19-2010 That would work. I also thought of just using a small spring. I've been busy and haven't had a chance to try anything yet.
Dave
Re: Rebuilding an HP 41 battery pack - Andreas Grund - 04-20-2010 David, The battery pack is kept in place by the force of the 4 spiral springs inside the battery pack. For my better understanding, which contacts are coroded? The thin copper layer in the battery compartment? Or the springs in the battery holder? In case you want to rebuild a battery case from scratch, this is very simple, based on 4 commercially available N size cell holders.
Re: Rebuilding an HP 41 battery pack - John Robinson - 04-20-2010 Hi David, I am in the same situation, and I thought about springs, but ruled them out, as I doubt they would stay in place. I am going to try some thin "spring steel" shaped pretty much to the same shape as the originals. I'll let you know how I go, if it works, I can send you some of the same steel - I have enough to build 100s of 82120 :-)
Cheers, Re: Rebuilding an HP 41 battery pack - DavidShenk - 04-20-2010 Thanks for the offer John. My thinking with the springs would be to solder them (if possible) right onto the ends of the batteries. I think that, you're right, they would move and cause problems otherwise. Fabricating a duplicate part would be ideal. Let me know how it goes.
Dave
Re: Rebuilding an HP 41 battery pack - DavidShenk - 04-20-2010 Hi Andreas, The rechargeable battery pack that I'm trying to rebuild isn't constructed the same as the N cell pack. Part of the rechargeable pack is taken up by the charging circuit. The rest of the pack contains 4 small NiCd cells tab-welded together, then each side of the pack has a piece of spring steel that makes contact between the batteries and the copper in the calculator. It is this flex that replicates the springs in the normal N cell holder. Of course, it is probably easier just to use N cells in the normal holder, but that's not the point!
Dave
Re: Rebuilding an HP 41 battery pack - Etienne Victoria - 04-21-2010 Hi David, You have mail. Cheers
Etienne
Re: Rebuilding an HP 41 battery pack - DavidShenk - 04-21-2010 Thank you Etienne for donating and sending the parts needed to complete this project. Everyone here is more than generous with their time and willingness to help others.
Dave
Re: Rebuilding an HP 41 battery pack - John Robinson - 04-22-2010 Hi David, Prototyping the replacement is quite sucessful, using 1/100" thick stainless steel, a little stiffer, but I think they will work fine. I take it Etienne sent some originals to you anyway, but if you want me to make you a couple contact me off forum.
Cheers, Re: Rebuilding an HP 41 battery pack - Alberto Fenini - 04-22-2010 ciao a tutti, Re: Rebuilding an HP 41 battery pack - Dave Shaffer (Arizona) - 04-22-2010 Beryllium is highly toxic - especially the dust, which might well be generated if you try to cut and file this to shape. Be careful!
Re: Rebuilding an HP 41 battery pack - Alberto Fenini - 04-22-2010 Thank you very much for the advice ! |