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Full Version: Re: HP 25C Battery help
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Never use an AC adapter without good, working, NiCd batteries in place, alkalines seems to be a good choice in your case (no warranties, but it was OK for me many years ago). Alkalines will last for many hours, opposed to the 2 hours typical with rechargeables.

If you decide to use rechargeables, it is advisable to recharge them in an external charger, not to risk your valuable calculator, since these are very sensitive to overvoltage events that the AC adapter may cause. An external charger will also allow you to use NiMH AA batteries, which last longer (hold more charge) than NiCd.

Finding such a spare battery pack is quite difficult. Fortunately, there are plenty of 21's for sale on ebay with battery pack. I understood you wished to use your 25 quite frequently so the best thing is to replace the batteries in the pack by 2 new NiCd ones, they'll last far longer.

... and you'll get a spare calc that is a real pleasure to use !

Well, I managed to kludge something together involving two AAA nickel metal hydride batteries and some electrical tape. I did it in such a way as to not damage or modify the calculator, and I can take out the AAA's and recharge them in my Rayovac battery charger. (Something tells me that AAA's will not last long in it) And, if I ever do find a battery pack, I can rebuild it with NiMH AA cells and use it instead.

Ian Primus
ian_primus@yahoo.com