The Museum of HP Calculators

HP Forum Archive 08

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hp31e /34c batteries
Message #1 Posted by Edwin Morales on 20 Mar 2002, 12:53 p.m.

I have two hp31e and hp34c calculators working with alkaline batteries (2 x 1.5 Volts = 3 Volts) instead nickel/cadmium (2 x 1.25 = 2.5 Volts). Both work without problems? Is it safe?

      
Re: hp31e /34c batteries
Message #2 Posted by David Smith on 20 Mar 2002, 5:39 p.m.,
in response to message #1 by Edwin Morales

I have never had any problems in Spice or Woodstock series machines using alkalines. Just remember to NEVER plug in the charger... but then one should NEVER charge any batteries in a Woodstock machine.

            
Re: hp31e /34c batteries
Message #3 Posted by Karl Schneider on 23 Mar 2002, 3:25 a.m.,
in response to message #2 by David Smith

I just bought a 34C locally (Vancouver, WA) without a battery pack or charger (or manuals or case!). I, too, noticed that the factory- specified rechargable AA batteries were rated at 1.25 V, while the disposable AA betteries are 1.5 V. I improvised by putting the 1.5 V batteries directly in the chamber in series, jumpered by a folded strip of aluminum foil. They fit snugly. The 34C seems to be working fine, but I was concerned about slow damage from slight overvoltage.

I visited Radio Shack this evening. The sales clerk said that freshly-recharged 1.2-V NiCd or NiMH AA cells can have 1.5-1.7 V, so there might not be a problem. Still, I'd like to know what the manual says. I guess I'll know when my CD set from the Museum arrives.

                  
Re: hp31e /34c batteries
Message #4 Posted by Edwin Morales on 23 Mar 2002, 7:55 p.m.,
in response to message #3 by Karl Schneider

Manual says: Use of any batteries other than Hewlett-Packard battery pack may result in damage to your calculator. A manual from April 1980.

A tech problem or a business? My calculators are working fine.

                        
Re: hp31e /34c batteries
Message #5 Posted by Andrés C. Rodríguez (Argentina) on 24 Mar 2002, 4:22 p.m.,
in response to message #4 by Edwin Morales

At least in my experience with a HP 25, alkalines are OK. I think that the circuitry allows for the not so large difference between a fully charged NiCD (perhaps 1.3V) and a regular alkaline (usually a little over 1.4 V).

The 1.5 V value comes from the old, zinc-carbon (non alkaline) batteries, and is used usually as a convention. A less than 10% tolerance seems almost logical.

While this makes sense to me as an Electronics Engineer, I can offer NO WARRANTY because I don't have any detailed data on the calculators circuitry and proprietary components HP used. This is just my personal opinion.

The alkalines may give you some 10 hours of service, while NiCd of the '80s offered about 2 hours, but a 500 charge-recharge cycles' life.


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