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HP Forum Archive 15

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HP 34C battery pack
Message #1 Posted by Steve from peru on 6 Nov 2005, 6:06 p.m.

I just found my old HP 34c and i am trying to get it up and running. The original battery doesnt seem to want to take a charge. Does anyone know the technical specs for these batteries, and how I might find a modern replacement. thanks.

      
Re: HP 34C battery pack
Message #2 Posted by Gerson W. Barbosa on 6 Nov 2005, 7:09 p.m.,
in response to message #1 by Steve from peru

Just read the recent thread Batteries for 41CV or 33E.

Gerson.

      
Re: HP 34C battery pack
Message #3 Posted by Paul Marin on 6 Nov 2005, 8:42 p.m.,
in response to message #1 by Steve from peru

I've been using 2 x AA 1.5v alkalines in my 33E for over 1 year. No problems

This is a quick no fuss fix only. It suits me fine. You can repair the existing pack based on info on this site

Paul

            
1.5V "AA" will break the battery contacts...
Message #4 Posted by Karl Schneider on 6 Nov 2005, 10:24 p.m.,
in response to message #3 by Paul Marin

... because they are longer, and depress the curved part of the contacts more. The contacts will fracture along the crease between the riveted flat part and the curved part.

There are two designs of Spice (31/32/33/34/37/38) battery pack; either can be disassembled and rebuilt properly with 1.2V rechargeable flat-top "AA" cells (without posts).

I would eventually like to use Katie Wasserman's procedure to install stronger fabricated contacts, allowing use of either longer 1.5V cells (jumpered by aluminum foil) or a rebuilt pack.

-- KS

                  
Re: 1.5V "AA" will break the battery contacts...
Message #5 Posted by Paul Marin on 7 Nov 2005, 6:15 p.m.,
in response to message #4 by Karl Schneider

Have had no such problems. Contacts have flattened yes, but remain this way with no other forces on them. The pressure of the batteries is very light. They will fracture if bent backwards and then re-flattened continiously, but if they stay as they are, there is no problem. I don't use the re-built pack therefore I never needed to readjust the contacts, therefore no fracture will occur unless I start fiddling with them. I have had to re adjust contacts in remote controls for eithertv's dvd's or stereo's and I've used pliers to pry them closer to maintain good battery contact and I've never had problems with fractures and some of these remotes are cheap units from China and Taiwan. My 2 cents worth

Paul

                        
Re: 1.5V "AA" will break the battery contacts...
Message #6 Posted by Karl Schneider on 8 Nov 2005, 12:39 a.m.,
in response to message #5 by Paul Marin

Paul stated,

Quote:
Contacts have flattened yes, but remain this way with no other forces on them. The pressure of the batteries is very light. They will fracture if bent backwards and then re-flattened continiously, but if they stay as they are, there is no problem.

If the contacts have flattened, then some metal fatigue has already taken place. The force of contact using longer cells is certainly higher than intended by design. Certainly, repeated flexing due to continual removal and re-installation of cells would fatigue the contacts faster. If you are using disposables (as indicated by "1.5V") and are also using the calc regularly, replacement will be required. That's why the HP LED-based models were designed for rechargables.

The two HP-34C's I bought on eBay turned out to have fractured battery terminals. I strongly suspect that this was caused by use of longer 1.5V disposables after the US$12 (in the 1980's!) rechargeable pack gave out. One of them was advertised as having good contacts, but one contact simply broke upon a light touch. It looked fine, but clearly was fatigued and cracked.

-- KS

                              
Re: 1.5V "AA" will break the battery contacts...
Message #7 Posted by Paul Marin on 8 Nov 2005, 5:19 p.m.,
in response to message #6 by Karl Schneider

Karl, I'm not debating that with constant bending that the contacts wouldnt break. The original rechargable pack flexes the contacts just like any electronic device that uses metal straps to engage the cells. I've just pressed mine flatter to the point where the AA's press lightly enough to make the contact. We are not talking imence pressure exerted here that flex the contacts millimeters each time they are inserted or removed. If mine break in the near future, I'll post a log of how long they lasted. PS The owner of this 33E I own is by coincedent my employer, who happens to be a mechanical Engineer. I did consult his knowledge on what I had done and he believes that the contacts should last once flattened.

Paul


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