Old HP Calculator? Give it a New Battery! 

I just purchased one of these, in the original plastic-box, with original power-supply and the soft leather-case, apparetly never used., still rolled up. It also has the manual, in Danish(!!). Only problem is, of course, the battery-pack. Incredible how, 50 years after it was manufactured, it still powers up and the keys give a nice tactile feedback. Bought it because I collect sliderules and this is The Sliderule Killer.. Paid 100 DKR, or about 15USD for it😊

Replaced the NiCads in my HP-21 and HP-25 with Eneloops (minor plastic surgery). New Life! And Original charger works great with the NiMh chemistry. Still use these to balance the checkbook; my everyday calcs are now the HP-50G and HP-Prime. We RPN engineers are becoming a rare breed! Long live RPN!

Just dug mine out. Now I have to remember how I ever got along without it being a retired NC programmer.

On the 2nd option you can actually place a couple furniture moving felt pads on the cover. They’ll keep it secure. Great video.

I've a Hewlett-Packard HP-15C app on every digital device that I can install one. RPL is the only way to go!

Hey thanks :) Picked up a nice calculator at the thrift store for 6 bucks! Just have to get it working now :P I hope that after rigging up a battery pack that the display is working alright hah!

A neat solution. Have adapted slightly by making copper plates stuck to the battery pack, to make a removable pack that can be used in other calculators, and leaving the calculator totally stock.

You can buy a 1000ma battery pack off of eBay for less than $20. Or for a bit more, you could get the 3000ma battery. From the listing: "The CL-1000 battery pack is designed to be used as a replacement for discontinued Hewlett-Packard HP82001A and HP82001B packs." Looks pretty much like the real deal too. I collect calculators, and the HPs are my favorites. Yesterday I bought a HP-20, a 41CX, and a 67. The 67 comes with a new battery. Same one as what the 35 uses. Curiously, I don't own a 35. :)

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Looking for Hp_C scientific button battery type? Identifications & battery's are missing. Has 3 button batteries.

Looking for hpscientific Calc button battery type. Battery door and Calc type are missing. Yes, had it since approx '73ish. Calc not like one ur showing. But approx 3x5" need 3 button batteries. Could b a 15C unit.

trivia why is it called hp 35?? it had 35 buttons

sorry ,, is that aaa or aa size

ANSWER QUESTION WHY IN 10BC A SIMPLE CALCULATOR FOR ADDITION AND SUBTRACTION WAS PLAYED WITH BY A COLLEEN ZAMBORIE COLLEEN THOMPSON IN A INCOHERENT WAY THAT CONFUSED IT AND YOU LET THAT GROUP PRETEND THAT THAT WAS HOW MUCH MONEY THEY HAD

Nice work play boy