How to open the 82033A battery packs?

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How to open the 82033A battery packs?

Postby Drulli » Thu Dec 25, 2014 10:02 pm

Hi all,
Merry Christmas to all hp enthusiast! :mrgreen:

I have bought a 82143A printer and a 82161A digital cassette drive recently. Both devices use the same type of battery packs, the 82033A. The batteries are from the original supply and thus they are dead more or less.

I guess I have found proper NiMH replacements, Akku Battery NiMH 1,2 V / 3,0 Ah 3000 mAh Sub C single cell (amazon).

Now I need to open the battery compartment and want to know, whether anyone has experience how to do it.
What is the best way? Where exactly the two halves are glued or clicked together? At the entire contact surface or somewhere particular? That would mean I have to cut the two have into to parts, cutting all around the pack!?
Does anyone has a photo how the packs looks inside?

Any hint, advice or info is very welcome.

best regards,
Drulli
Drulli
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Re: How to open the 82033A battery packs?

Postby Garth » Thu Dec 25, 2014 10:42 pm

I don't know how to get it apart neatly; but do you have a suitable way to charge the NiMH batteries? Charging works differently from that of NiCd. I looked into it for a product at work a few years back, but I still don't know enough about it to know if you can do the job with the existing HP non-intelligent charger. I expect that you'd at least have to keep an eye on the temperature and stop charging when the batteries are fully charged and begin to warm up. For the work project, I ended up going with a small lead-acid battery which is much easier to deal with. We had a situation where the device the battery was going into would keep getting moved in and out of the sun while on the charger on a vehicle, so we couldn't go by temperature or the corresponding voltage dip.
http://WilsonMinesCo.com (60 HP-41 links on the links page)
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Re: How to open the 82033A battery packs?

Postby Drulli » Sun Dec 28, 2014 1:40 pm

Good point, Garth.

My assumption was that the printer and cassette drive use the same power regulator circuit as it is in the rechargeable battery pack for the hp-41.

I looked for the printer service manual (or cassette drive) but unfortunately I could not find it in the web. (I know it is existent, in a post in the hp-museum someone stated he has it. I will send him a request but there is no valid email available. If you or anybody else can give me a hint where to find it, would be great.)

What I found is a hand drawn schematic of the printer modules, incl. PSU (power supply unit).
If it is complete or correct I don't know. But it looks reasonable.

It shows that the normal hp charger AC voltage is bridge-rectified (without load it should be around 22Vdc) and smoothed by a 100uF Elko. After that a pull down resistor (8.2 Ohm, really so small, or kOhms?) provides around 6.5Vdc to the positive batteries contact(I measured it on my printer. There is quite a AC ripple on the dc voltage, I don't know how the NiMH handle that, I assume it is ok.)

In the data sheet of the NiMH subC batteries the max. charge voltage is 1.5V. Thus 1.625V (6.5V/4 batteries) is a bit too much, especially if it is provided permanently. For single NiMH I measure a charging voltage of 1.32V on a standard battery charger.

Furthermore there is no kind of current regulation / limitation, it is difficult to predict how high the charging current of the NiMH will be. Trickle charging current is 30..150, max overcharging is 300mA. Comparable NiCd can handle the same amount of current or even more. The old NiCd suck about 10mA.

Conclusion:
Most easiest way to solve that issue would be to modify the pull down resistor in a way that only 5, 5.5 V is provided to the battery contacts.
Most elegant way would be to put a little 78L05 power regulator circuit (like the one in the rechargeable calculator battery packs) into the PSU which provide the right voltage for the NiMH.

I will think about it and put it on my project list.

Ok, the post is far too long. But anyhow, may helpful in some kind.

Kind regards,
Ulrich
Drulli
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Re: How to open the 82033A battery packs?

Postby Garth » Mon Dec 29, 2014 1:03 am

I hate to post the obvious, but sometimes I have needed the recommendation myself, to do a web search. I typed "charge NiMH batteries" into ixquick.com (I don't use google) and immediately got two million results, starting with:

http://www.powerstream.com/NiMH.htm NiMH Battery Charging Basics
http://www.greenbatteries.com/nimh-battery-charger-faq/ NiMH Battery Charger FAQ
http://batteryuniversity.com/learn/arti ... al_hydride BU-408: Charging Nickel-metal-hydride
http://WilsonMinesCo.com (60 HP-41 links on the links page)
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Re: How to open the 82033A battery packs?

Postby Drulli » Mon Dec 29, 2014 8:09 pm

Yes, there is a lot of know how available in the net about charging NiMH. And I admit I don't know enough about it to be very sure how to deal with the Printer battery.

I have looked at it from a more practical angle.
1. In my hp-41 rechargeable battery pack I replaced the NiCd against NiMH once. That works fine. Most likely not the best treatment for the batteries, but that is a minor issue. The NiHM are charged via a Voltage regulator over a zener diode. Thus this solution should work for larger batteries as well, in principle.

2. Just replacing the NiCd or the printer battery pack seems to work as well, even though it might be even worse for the batteries. I found on ebay a shop that sells a 1:1 replacement for the printer standard battery pack. I contacted them and they stated it works ok, but the printer should not be connected permanently to the standard hp AC charger , means not permanently connected to the main power supply.
http://www.ebay.de/itm/SUPER-Akku-HP-97-97S-82143A-82161A-82162A-NiMH-bestuckt-/320527047205?pt=LH_DefaultDomain_77&hash=item4aa0e69a25

My conclusion is: either solution 1, if it really works (I need to simulate it on a breadboard first).
Or solution 2, build your own NiMH based battery pack with the possible to open the pack to take discharged NiMHs out and charge each of them separately. Assuming that a fully charged NiMH battery pack has really no problems to work in the printer, as claimed by that company.
Drulli
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Re: How to open the 82033A battery packs?

Postby Drulli » Thu May 07, 2015 7:38 pm

Follow up:
I refurbished the Battery Pack 82033A.
With a knife and a little saw I cut the pack into pieces.
From Amazon I bought NiMH rechargeable batteries. Type SubC, 1,2V, 3,0Ah.
After I arranged the new batteries properly in the battery housing, I glued the two halves together. Not very difficult.

For charging the packs I use the standard HP charger. Even after a heavy discharge of the battery the charging current was not larger than 200mA.
That's absolutely ok for this type of batteries.
The temperature of the device during charging (inside the device) was not hotter than a little warm, if even.
Maximum voltage I measured after an overnight charging session was 5.4 Volts. Excellent!

My Printer and Cassette Drive work now very reliable and with the new much higher capacity of the batteries "Low Power" is not an issue any longer.
I posted a bit more detailed description including photos on my homepage. (best occasion to improve your German) :mrgreen:
http://www.schwalvenberg.com/de/hp-41cx/111-hp-82033a-battery-packs-akku

UPDATE:
I invested some time to translate the article about the battery pack refurbishment (and others) into English and put it online. Just in case someone wants to see some details.
http://www.schwalvenberg.com/en/hp-41cx/115-hp-82033a-battery-pack-refurbishment
Drulli
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