Battery Pack for HP35/45... - a good solution found


I have been looking for a battery pack for a HP 35. I have tried:
International Calculator company in Orlando and went onto their website > ( and ordered the battery pack there. HP82001BR Price: $39.00

They ask for the old battery pack, since the plastic parts are no more available and send me another pack with fresh batteries and the contacts perfectly welded. It looks like new.

I found the solution perfect for a reasonable price. The service is good too (in fact they sent the new pack, before I could return the old one)

Just in case somebody gets the same problem

Best regards




I should go into business doing that, as it cannot be hard to crack open a battery pack and replace the cells.

Tool Kit:

- Dremel rotary tool with cutoff wheel
- super glue
- soldering iron
- solder
- spring contacts
- small flathead screwdriver
- patience
- a steady hand

Still, you're a satisfied customer. I'm looking at their site now, so they must be doing a good job.



there is someone on ebay selling a not-in-a-stock-case new bat pack for $15. if you are using, not collecting, then that is at least more affordable.


It is not cheap, but this is something which is not needed too often. Deduct the cost of the rechargeable batteries and you may find the price more reasonable.

Lately I had to replace the rechargeable battery for my IBM Thinkpad. The price (in Switzerland) is around $300. No manual work to be done……

Should you start your own business with much better price and same performance, let us know



To All, The batteries I have found are normally used in Cordless handset phones, and I obtained them in the UK from RS Components, ( stock No.595-491 and cost £7-20 plus local tax. They are Ni-Cad 3.6V/700mAh, and I have used them in three of my HP35's and a HP45 with no problems.
They come as a unit with two tags and I just solder on flying leads (very thin wire is best) which I then solder to the battery terminals in the back of the calculator, I solder them halfway down the terminal so as not to modify the ends that might want to be used in the future. As they are shrink wrapped with insulator I just let them rest in the battery compartment.
It might be possible to take the three cells and incorporate them into the HP battery pack after cutting around the joint on the plastic.
The other thing I do is to take 3 AA Alkaline cells and put them into a HP battery pack again after cutting around the joint to separate the two halves.
This is a solution I have used very succesfully in my HP25, just take 2AA's and place them in the battery pack from your HP25,21,27,29 etc.
I have some pictures to show you what I have done.
RS Components has a place in the USA called "Allied Electronics in Texas, their web address is, I found this from the RS catalogue I receive regularly.
I hope this is of some help, let me know if it's helpful or makes sense, please feel free to let others know and call me if you want more info if I can provide it.
Regards Richard.


My local battery store will do the same thing using 1800 maH metal hydride cells for $16.50 plus tax. Any Batteries Plus, Batteries, Etc., or similar stores will do it for a similar price.

If you just need a workable pack, you can get a heat shrinked three cell Nicad portable phone battery on sale for $2.00, strip the leads about an inch and trim the length. Align the leads along the gaps between the cells and tape them down so they do not flop around. Insert pack in the calculator. Enjoy das blinkinlights.


I was in Boston last year, looking around stores, when I joined my family in a doll store. They had rolls of adhesive copper strips used to wire doll houses.

I've used lots of this to rebuild battery packs with flat wires (it solders great), as well as to adhere in the two notches between phone packs and Lithium AA packs I've built. It works great as a classic series pack.

You never know where you'll find useful stuff....


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