Battery Pack for HP 21


My apologies for the lengthy link.

I recently bought an HP 21 with a 'repaired battery case'. In fact, the battery case was busted in order to accommodate 2 AA cells. It is not pretty and I have to use a screwdriver to 'pry' open the case to access the batteries. I can barely put the cover back on afterwards and it is in fact in two separate pieces. What a shame since the calculator works perfectly. I bought it because I needed a non-programmable for an upcoming test, and only an HP will do!! The charger that came with unit may be functional but I have not yet been able to test it.

My question concerns the ebay link above. Will this battery pack, stated as being a Sanyo NBP-25 battery pack for a HP 27 Scientific Calculator, work in my HP-21? If so, do you think the HP 21 charger would work with it, assuming it is functional?


Jeff Kearns

P.S. I also bought a 32E, so I am covered no matter what!

Edited: 24 Feb 2008, 4:33 p.m.



all Woodstocks had identical batteries. I do not have any specific info about this particular type of pack, but IF it works with a HP27 as the vendor claims, it shall work with your HP21 as well - with and without a charger. Since the 21 has no continuous memory, it won't be as critical to try this pack. I'd suggest you ask the vendor a bit, e.g.: Do the batteries hold a charge still? When where they bought? etc.

HTH, Walter


it don't look good.
ask for a better picture.


Hi Jeff,
From the picture, the thing doesn't look like a woodstock battery pack. Would need to see the ends of it to tell for sure.

Also, for what it's worth, I took a CET (certified electronic technician) exam last year where programmables were banned also...but I convinced the instructor to let me use an hp67, as it has a volital memory :) regards, Hal



Thanks for your input. I asked the question suggested above and received the following reply:

"The battery pack, which is a single 2.4 volt unit, has never been used or recharged. It current-ly, no pun intended, is at 1.53 volts dc, just checked it. I bought it in 1981 as a spare for my HP 27 Scientific Calculator. I never had a need to replace the original battery pack in the calculator. The calculator had an internal recharger. What is a Woodstock Charger??, some kind of cop at a musical event ?? I no longer have the hp27."

I decided not to bid on this particular unit... I will keep looking!

Thanks again,

Jeff in Gatineau, QC


Expected something like this. That was the reason for writing "if" in capitals above :)

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP 21 - How to troubleshoot? Adam Vaughn 13 1,465 10-02-2013, 09:40 AM
Last Post: Adam Vaughn
  HP 50G Multi Lingual Pack – Polski Software49g 3 721 04-10-2013, 10:40 AM
Last Post: Massimo Gnerucci (Italy)
  HP 41 Battery Pack Rebuild John Ratard 0 1,473 09-29-2012, 01:37 PM
Last Post: John Ratard
  HP-41 Quiz: How to pack 100k in ROM? (on-line) Ángel Martin 10 1,301 09-02-2012, 10:35 PM
Last Post: Luiz C. Vieira (Brazil)
  Unknown battery pack Nick R 4 811 05-27-2012, 01:32 AM
Last Post: Nick R
  Disassemble Battery Pack 82028B (woodstock) Jacques Karensky 0 482 05-19-2012, 03:39 AM
Last Post: Jacques Karensky
  aOT--Battery/battery contact care advice needed Matt Agajanian 0 483 04-24-2012, 07:35 PM
Last Post: Matt Agajanian
  HP-35A/21 D.MS<-->Decimal degrees routines Matt Agajanian 9 1,268 03-29-2012, 11:03 AM
Last Post: Matt Agajanian
  21, 45, 32E--which should be next? Matt Agajanian 14 1,606 03-25-2012, 02:48 AM
Last Post: Thomas Radtke
  If the 21 came after the 45...? Matt Agajanian 5 784 03-24-2012, 05:45 PM
Last Post: Matt Agajanian

Forum Jump: