Rebuilt HP-67 Batteries Recharge Cycle

Hi all,

To play it safe, I purchased these

HP-67 1000 mAh Battery Pack

for my Classics & HP-67 instead of the 2000 mAh packs.

With the calculator turned off during the entire cycle, what is the length of time I should allow for the full charging session?



Hi Matt, how are you, hope with this new pack you will succed to keep the comparment door closed!
Have you found indeed where was the problem?


Thanks Aurelio.

Well, while my 67's card reader was being reconditioned, the tech found a replacement latch which provided the perfect fit & fix. Although it's a different coloured latch, that difference will serve as a good disciplinary reminder to be extra careful with this battery door.

As for what the glitch was, I'm not certain. But, now that the latch issue has been remedied, I shall endeavor to be a bit more attentive and cautious nonetheless. If I do find out what the issue was, I'll let you know.

Edited: 19 May 2012, 2:48 p.m.



for 1000 mAh, give it a 22 hrs. charge with the 82010A with calculator being switched off all the time.



WHOA! Is that from a battery's full discharge? What about when the BP's depletion in the 67 triggers the low battery dot on the 67? Surely not 22 hours for that recharge cycle?


There's no advantage to using lower capacity cells, unless you need to charge to full (but lower) capacity quickly.

Higher capacity cells won't harm the calculator; they operate at the same voltage as the lower capacity cells. The charge current will be the same with either, as that is determined by the charging circuitry, not the cell. Since the charging current is the same, the charging time is directly proportionate to the capacity.

Edited: 19 May 2012, 4:30 p.m.


WHOA! Is that from a battery's full discharge? What about when the BP's depletion in the 67 triggers the low battery dot on the 67? Surely not 22 hours for that recharge cycle?

I would have stated that the new pack is approximately 3x the capacity of the old pack, therefore the new pack will take approximately 3x the time to charge. ISTR the old pack was spec'd at 10 to 14 hours for a full charge, therefore the new pack will take 3x10 to 3x14 or 30 to 42 hours.

22 hours is probably a good refresher charge when the pack is not empty.

You can tell when the pack is full if all the cells are elevated in temperature. The '67 is such a slow charger that the only time the cells will heat is when the cell is full. So if all the cells are heating, all the cells are full.

It is good to charge the pack to "every cell is full", otherwise the weaker cell (that was more empty) gets less charge and will be even more empty next time. Eventually the weaker cell will be damaged, and it could happen the next time you discharge it if the weak cell reaches 0v and the other cells keep the system operating. Then the weaker cell will experience reverse current flow, and that kills it.

I rebuilt my own '67 pack and used 1400mAh cells. It takes 3-4 days to fully charge.


Pardon, but what does ISTR mean?


NiCad cells adapt to their usage. Unused or little used they conttinually lose capacity. I suggest rebuild with Eneloop Nimh cells that hold their charge up to a year and have no usage memory. I use them in all my devices using AA calls. Sam


ISTR means "I Seem To Recall"


Thanks. As I am very traditional and would rather spell out what I'm trying to say, I haven't kept up with all this shorthand which texting seems to have popularised.

Edited: 21 May 2012, 1:47 p.m.


So, from what you're saying, since I'm using the original/stock HP charger with these new 1000 mAh packs, even from the first appearance of the low battery warning, I'll need to set aside at least two days to recharge the 67, right?

I guess there's no such thing as a third party charger for classics and/or just the packs which would be safe for charging these new 67 battery packs more quickly. Is there?

Edited: 21 May 2012, 3:44 p.m.

Possibly Related Threads…
Thread Author Replies Views Last Post
  HP 50g : More on best rechargeable batteries Miguel Toro 1 1,768 12-12-2013, 05:31 PM
Last Post: David Hayden
  HP 50g : Best rechargeable batteries ? Miguel Toro 14 4,704 11-16-2013, 03:35 PM
Last Post: Dieter
  Storing HP-42S without batteries Yriarte 4 1,753 10-19-2013, 08:32 PM
Last Post: walter b
  HP-12C batteries Yriarte 4 1,894 10-12-2013, 10:39 PM
Last Post: Yriarte
  BATTERIES' SWAP ON HP 48GX aurelio 7 2,613 10-06-2013, 07:50 PM
Last Post: aurelio
  HP-67 won't run on batteries David Ramsey 5 1,965 04-18-2012, 12:15 AM
Last Post: David Ramsey
  N batteries for HP 41's WaltMaken 17 4,664 01-13-2012, 01:08 AM
Last Post: Håkan Thörngren
  HP-15c LE Batteries Michel Beaulieu 2 1,293 09-02-2011, 03:13 PM
Last Post: Kiyoshi Akima
  What is the celestial cycle for Red Dots on TAS? Michael de Estrada 10 2,560 06-05-2011, 09:15 PM
Last Post: aj04062
  HP 15C Batteries (Update) BrianDH 7 2,176 03-28-2011, 03:48 PM
Last Post: Bill (Smithville, NJ)

Forum Jump: