Load time for HP41 accu pack?

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Load time for HP41 accu pack?

Postby floppy_stuttgart » Fri Jan 14, 2022 6:42 pm

Hello,
how much time should I keep the accumulator charging? 6h? 12h? Last time when I kept it 6h, it was quite quick empty (1 month) despite low use time (in HP41CX).
I was just wondering why it was so short: perhaps it was not charged long enough.
Any advice is welcome.
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Re: Load time for HP41 accu pack?

Postby Garth » Fri Jan 14, 2022 9:13 pm

Note to Americans, or maybe to native English speakers in general: "Accumulator" is apparently what Germans say when they mean "rechargeable battery."

Floppy: I'm not familiar with the "accu pack." Is there some danger of overcharging if you just leave it overnight?
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Re: Load time for HP41 accu pack?

Postby floppy_stuttgart » Sun Jan 16, 2022 12:57 pm

I made following:
- loading 12h the chargeable batteries
- testing with https://calc.fjk.ch/hp-41-akkutest/
Result: 3.1333
So, the runtime on an HP41CX (connected to a PC via Pilbox; Nov64d and double-X-Memory in it) with full charged batteries is 3h 13min 33s.
Personally, I am not so impressed. I would have expected a bit longer.

What is your experience with the running time with rechargeable and/or not rechargeable batteries? (no magnet card reader; because I remember few time ago, this kill quick the batteries).
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Re: Load time for HP41 accu pack?

Postby dlachieze » Sun Jan 16, 2022 1:46 pm

Here is the original instruction card for the HP 82120A battery pack, it says 12 to 16 hours to fully charge the pack:

IMG_20220116_143721_edit_849256533861557.jpg
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Re: Load time for HP41 accu pack?

Postby Garth » Sun Jan 16, 2022 5:17 pm

In the late 1980's at work, I did battery-life testing on different kinds of 9V batteries for one of our products, and got, very approximately:

  • 80 hours for lithium (primary, ie, non-rechargeable, rather new on the market, and very expensive)
  • 40 hours for alkaline
  • 20 hours for zinc-chloride
  • 10 hours for carbon-zinc
  • 7 hours for nickle-cadmium for one charge. The NiCd battery was not totally brand new, but relatively new and in good condition.
I repeated the test many times and got pretty consistent results. I might have tried different brands of each too, but I don't remember.
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Re: Load time for HP41 accu pack?

Postby floppy_stuttgart » Mon Jan 17, 2022 11:19 pm

dlachieze wrote:Here is the original instruction card for the HP 82120A battery pack, it says 12 to 16 hours to fully charge the pack:

IMG_20220116_143721_edit_849256533861557.jpg

Thanks.
And then how many hours the battery should hold?
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