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HP21 batteries



#8

Hi there, new to the forum. I have an HP21 which I bought for fun at a garage sale but am currently relying upon as I lost my beloved 41CV. I don't see how to remove the rechargable AA batteries from the pack/holder. The calc. will only work now when plugged in, I would like to replace the batteries, any suggestions? thanks in advance....


#9

Actually, replacing the batteries is pretty simple.

Use wire cutters or a knife to trim out the central plastic spline that runs between the two batteries.

Now you can easily remove the old batteries, clean out any corrosion, and simply insert a fresh pair of "AA" alkaline or NiCads. Make sure you get the polarity right!


#10

http://www.hpmuseum.org/howtohp/howtohp.htm


and


http://www.hpmuseum.org/batts/battery.htm


#11

I cut the back piece as shown, thanks for the help! I think the batteries I pulled out are circa 1975 like the calculator


#12

Be sure to clean off the battery terminals of the pcb from corrosion, if applicable;-)


Raymond


#13

ok now here's a dumb question, can I run nickel-metal-hydride batteries in place of the NiCDs which I haven't been able to find? thanks again...


#14

Yes, NiMH cells work wonderfully in these machines. 1800maH cells will run it for three times as long as the originals (if you charge them for three times as long).


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