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Neve · (This post was last modified: 09-22-2017 09:21 PM by Neve.)

Hi,

Can anyone be so kind as to what NiMh battery cell to use to rebuild the battery packs of my HP82162A, HP82143A and HP82161A cassette drive? All I need is a reference and a supplier.
Please do not start an argument about NiCd vs NiMh, my mind is already set.

Thank you so much for your time.

Dieter · (This post was last modified: 09-22-2017 10:14 PM by Dieter.)

(09-22-2017 09:20 PM)Neve Wrote: Can anyone be so kind as to what NiMh battery cell to use to rebuild the battery packs of my HP82162A, HP82143A and HP82161A cassette drive? All I need is a reference and a supplier.

The battery pack for these devices uses four Sub-C (SC) batteries. I would recommend you contact a professional service that rebuilds battery packs (not only for calculators) because only this way the four cells can be adaequately welded together. If you want to do it yourself you would have to get flat-top batteries with soldering tabs – but this is not the preferred method.

Quality-wise most major brand batteries should be fine, especially Sanyo and Panasonic. AFAIK Sanyo now is a part of Panasonic, so this probably is the obvious choice. For the HP printers I'd pick a general use battery, not the one with the highest possible capacity. Special versions for high drain applications are not required, you won't need something that may supply 20 A or more. ;-) Maybe there also is a local service near you that can both provide the four cells as well as do a professional cell replacement for you.

Note 1: Complete replacement packs with current NiMH batteries are readily available, cf. here.
Note 2: If you want to change the cells yourself there are also welded packs of four SC batteries available, cf. here. You can even choose the battery type, and there also is a service to have the complete replacement done for a moderate fee.

Both examples are German suppliers, but you should be able to find similar offers in your region as well.

Dieter

Neve · 09-22-2017, 10:32 PM

(09-22-2017 09:53 PM)Dieter Wrote:
(09-22-2017 09:20 PM)Neve Wrote: Can anyone be so kind as to what NiMh battery cell to use to rebuild the battery packs of my HP82162A, HP82143A and HP82161A cassette drive? All I need is a reference and a supplier.

The battery pack for these devices uses four Sub-C (SC) batteries. I would recommend you contact a professional service that rebuilds battery packs (not only for calculators) because only this way the four cells can be adaequately welded together. If you want to do it yourself you would have to get flat-top batteries with soldering tabs – but this is not the preferred method.

Quality-wise most major brand batteries should be fine, especially Sanyo and Panasonic. AFAIK Sanyo now is a part of Panasonic, so this probably is the obvious choice. For the HP printers I'd pick a general use battery, not the one with the highest possible capacity. Special versions for high drain applications are not required, you won't need something that may supply 20 A or more. ;-) Maybe there also is a local service near you that can both provide the four cells as well as do a professional cell replacement for you.

Note 1: Complete replacement packs with current NiMH batteries are readily available, cf. here.
Note 2: If you want to change the cells yourself there are also welded packs of four SC batteries available, cf. here. You can even choose the battery type, and there also is a service to have the complete replacement done for a moderate fee.

Both examples are German suppliers, but you should be able to find similar offers in your region as well.

Dieter

Hi Dieter,

That is awesome, thank you!!!! I’ve been living in France for several years now, so Germany is not too far.

Dieter · 09-23-2017, 08:02 PM

(09-22-2017 10:32 PM)Neve Wrote: That is awesome, thank you!!!! I’ve been living in France for several years now, so Germany is not too far.

German Mail / DHL also ships to France. ;-)

For the record: akkuplus.de also seems to have solutions for the Classic's battery pack as well as the 41's 82120A pack (consisting of four 1/3 AAA cells). Some years ago I had a similar pack built by a local battery supplier who also offered this service.

Dieter

Neve · 09-24-2017, 12:37 AM

(09-23-2017 08:02 PM)Dieter Wrote:
(09-22-2017 10:32 PM)Neve Wrote: That is awesome, thank you!!!! I’ve been living in France for several years now, so Germany is not too far.

German Mail / DHL also ships to France. ;-)

For the record: akkuplus.de also seems to have solutions for the Classic's battery pack as well as the 41's 82120A pack (consisting of four 1/3 AAA cells). Some years ago I had a similar pack built by a local battery supplier who also offered this service.

Dieter

Yes, I know they do. I just bought cells from eBay, from them, to rebuild a (HP41) HP82120A accu-pack. It works but for some reason was charged at 5.8V when I got it. I think this one has been overcharged and/or is defective. This concerns me a bit, to be honest. I have no idea how long it’s gonna last before failing....

Dieter · 09-24-2017, 07:45 AM

(09-24-2017 12:37 AM)Neve Wrote: It works but for some reason was charged at 5.8V when I got it. I think this one has been overcharged and/or is defective.

Why do you think it is? That's 1,45 V per cell.
No, a charged pack should not read 4x1,2 = 4,8 Volts.

Dieter

Neve · 09-24-2017, 07:50 AM

(09-24-2017 07:45 AM)Dieter Wrote:
(09-24-2017 12:37 AM)Neve Wrote: It works but for some reason was charged at 5.8V when I got it. I think this one has been overcharged and/or is defective.

Why do you think it is? That's 1,45 V per cell.
No, a charged pack should not read 4x1,2 = 4,8 Volts.

Dieter

Ooh, I thought theses were the usual “normal” 1.2V/cell. My bad... Maybe I’m completely wrong about this. I may have been confused by the fact that rechargeable N-Cells are 1.2V.
If it helps, the one I got are black, not like the apple green shown on their website.

Cheers

Neve · (This post was last modified: 09-24-2017 08:01 AM by Neve.)

Dieter,

The link you provided earlier stipulates that the combined cells deliver 4.8v...

Dieter · (This post was last modified: 09-24-2017 11:29 AM by Dieter.)

(09-24-2017 08:01 AM)Neve Wrote: Dieter,

The link you provided earlier stipulates that the combined cells deliver 4.8v...

1,2 V is just the nominal (!) voltage of NiCd and NiMH cells. The actual voltage is different. Fully charged and without load it usually is higher than 1,4 V and when completely depleted it approaches 1,0 V (with load applied) or even drops slightly below this. Yes, these are "normal 1,2 V cells".

No NiCd or NiMH cell produces a constant voltage of 1,2 V. This is just a nominal value. Take a look at the charge/discharge curves in the various manufacturers' data sheets. For instance here (GP17AAAH, a typical 1/3AAA cell). Consider the "low rate discharge" graph. Without load (i.e. 0 mA) the voltage probably is even slightly higher.

Dieter

Sadsilence · (This post was last modified: 09-25-2017 10:03 AM by Sadsilence.)

(09-22-2017 09:20 PM)Neve Wrote: Hi,

Can anyone be so kind as to what NiMh battery cell to use to rebuild the battery packs of my HP82162A, HP82143A and HP82161A cassette drive? All I need is a reference and a supplier.
Please do not start an argument about NiCd vs NiMh, my mind is already set.

Thank you so much for your time.

Hello,

for HP82143A etc. packs I am using following cells with very good results:

https://www.reichelt.de/Industriezellen/...ANGUAGE=FR

Those are LSD cells, so self discharge rate is only around 15-20% each year where as default NiMH/NiCD cells are completely (self) discharged and ruined after such a period without recharging (collector items like old HP calculator stuff normally are not used on a daily base).

I feel there is also a version with solder tails around. Sorry, no link.

For classics and woodstock series I prefer

https://www.reichelt.de/Cellules-industr...xus%2B2100

or

https://www.reichelt.de/Cellules-industr...xus%2B2100

for same reason.

Of course, contrary to akkuplus (which I can recommend, too) you have to assemble, weld or solder packs by yourself.

Best regards,

for same reason

Neve · 09-24-2017, 06:43 PM

(09-24-2017 05:56 PM)Sadsilence Wrote:
(09-22-2017 09:20 PM)Neve Wrote: Hi,

Can anyone be so kind as to what NiMh battery cell to use to rebuild the battery packs of my HP82162A, HP82143A and HP82161A cassette drive? All I need is a reference and a supplier.
Please do not start an argument about NiCd vs NiMh, my mind is already set.

Thank you so much for your time.

Hello,

for HP82143A etc. packs I am using following cells with very good results:

https://www.reichelt.de/Industriezellen/...ANGUAGE=FR

Those are LSD cells, so self discharge rate is only around 15-20% each year where as default NiMH/NiCD cells are completely (self) discharged and ruined after such a period without recharging

These cells are Ni-Mh. That’s what it says.

Thank You

Massimo Gnerucci · 09-24-2017, 06:45 PM

(09-24-2017 06:43 PM)Neve Wrote: These cells are Ni-Mh. That’s what it says.

Thank You

NiMh LSD (Low Self-Discharge)

Nate Martin · 09-24-2017, 06:51 PM

You might also want to look through some of the past threads for ideas. My current favorite is using rechargeable NiMH N-cells in the standard battery holder for the 41C. I use a charging adapter to allow the cells to fit in a standard AA charger. There were also several persons looking into using LiPo batteries and 5v boost circuits.

Neve · 09-24-2017, 07:05 PM

(09-24-2017 06:51 PM)Nate Martin Wrote: You might also want to look through some of the past threads for ideas. My current favorite is using rechargeable NiMH N-cells in the standard battery holder for the 41C. I use a charging adapter to allow the cells to fit in a standard AA charger. There were also several persons looking into using LiPo batteries and 5v boost circuits.

Yes, I’ve been looking into that option as well. Do you know how they compare to a Ni-Mh power pack in terms of longevity? I use my 41 on a daily basis including the card reader (but less).

Thank You

Dieter · (This post was last modified: 09-24-2017 07:21 PM by Dieter.)

(09-24-2017 05:56 PM)Sadsilence Wrote: for HP82143A etc. packs I am using following cells with very good results:
https://www.reichelt.de/Industriezellen/...ANGUAGE=FR

I hope you have access to a device for welding solder tabs to these cells. Never solder directly to any kind of battery contact.
But you already said it:

(09-24-2017 05:56 PM)Sadsilence Wrote: I feel there is also a version with solder tails around. Sorry, no link.

Yes, there is. Here is a version with solder tabs. NiMH cells with low self discharge ("ready to use") and solder tabs generally seem hard to get.

(09-24-2017 05:56 PM)Sadsilence Wrote: Those are LSD cells,

Since not everyone seems to be familiar with this term: this stands for NiMH batteries with extremely Low Self Discharge. This means you can charge them now, put them in a drawer and when you want to use them on Halloween next year (!) they are ready to power your flashlight. Or your calculator. ;-)

(09-24-2017 05:56 PM)Sadsilence Wrote: Of course, contrary to akkuplus (which I can recommend, too) you have to assemble, weld or solder packs by yourself.

That's the essential point. ;-)

Dieter

Neve · 09-25-2017, 03:26 AM

Thank you all for your replies.
Now, I have rebuilt the HP41 battery pack a coupe of days ago.
It was originally delivering 5.8v. Now it shows 4.94v. Even after 10h or so (I guess...) of charging it doesn’t go back up to 5.8v. Is this normal? I guess it would be since the original charger was not designed to charge Ni-Mh batteries. But I just want to make sure.
What are the risks of damaging it if I overcharged? I’m not sure how long I left it charging as I just recently read that 10h was the max time.

On a side note, I also read that the charger is just a transformer. No electronics inside. The electronics inside the pack is what regulates the charging cycle. Do I understand this right?
If this is the case, can it be modified to charge faster and/or more efficiently? If so, how?

I know I may sound a bit confused... And I guess I am. I’m definitely not an EE!

Thank you.

Dieter · (This post was last modified: 09-25-2017 09:03 AM by Dieter.)

(09-25-2017 03:26 AM)Neve Wrote: It was originally delivering 5.8v. Now it shows 4.94v. Even after 10h or so (I guess...) of charging it doesn’t go back up to 5.8v. Is this normal? I guess it would be since the original charger was not designed to charge Ni-Mh batteries. But I just want to make sure.

Both NiCd and NiMH batteries are charged with constant current. And that's exactly what the circuitry in the 82120A pack provides. It should deliver something like 13...16 mA. I am not sure about the capacity of the original 1/2N cells, but if we assume 70 mA this would mean a charging time of 70/15*(1,2...1,4) ~ 6 hours (assuming the calculator is off). In general, the charging time is the battery capacity divided by the charging current, times an efficiency factor which for NiCd and NiMH is about 1,2 (a bit less for high currents and a bit more for lower ones, here often a 1,4x factor is stated).

Re. the 5,8 V 4,94 V thing: this is the first time I hear of a NiMH battery where charging substantially reduces the voltage. That's hard to believe, I'd say there was something wrong with the 5,8 V measurement. But you're the only one how can know. #-)

(09-25-2017 03:26 AM)Neve Wrote: What are the risks of damaging it if I overcharged? I’m not sure how long I left it charging as I just recently read that 10h was the max time.

Overcharge will heat up the batteries and finally damage them. However, the relative charging current with today's 170 mAh cells is merely 15/170 = 0,09 C so that a full charge would mean about 15 hours, and exceeding this time a bit should not harm the batteries.

Please note that the charging time refers to a completely empty battery pack. So for a halfway depleted battery it's only half that time!

(09-25-2017 03:26 AM)Neve Wrote: On a side note, I also read that the charger is just a transformer. No electronics inside.

Right. There is not even a rectifier, the output is AC.

(09-25-2017 03:26 AM)Neve Wrote: The electronics inside the pack is what regulates the charging cycle. Do I understand this right?

Yes. You should take a look at this site, also consider the links down the page. But note that there were different versions of the 82120A which may have different electronics inside. Early samples featured a 5 V regulator and other differences (e.g. here), so you have to check what you got!

(09-25-2017 03:26 AM)Neve Wrote: If this is the case, can it be modified to charge faster and/or more efficiently? If so, how?

Since I am not an EE either I will not suggest any modifications. But AFAIK the 78L12 can handle up to 100 mA and the AC-adapter also has plenty of power (it was also used to charge the Sub-C cells in the printer's battery pack), so this should not be much of a problem. But there still is no charge control, so you should not choose a higher charging current than, say, 20 mA which – for your new 170 mAh cells – means a max. charging time of 12 hours. If you got the version with a 78L12 and 365 Ω resistor I'd say the latter may simply be replaced with 250 Ω – but again: I am not an EE so let's hear what the experts have to say.

Dieter

Sadsilence · (This post was last modified: 09-25-2017 09:53 AM by Sadsilence.)

(09-24-2017 07:13 PM)Dieter Wrote:
(09-24-2017 05:56 PM)Sadsilence Wrote: for HP82143A etc. packs I am using following cells with very good results:
https://www.reichelt.de/Industriezellen/...ANGUAGE=FR

I hope you have access to a device for welding solder tabs to these cells. Never solder directly to any kind of battery contact.
But you already said it:

(09-24-2017 05:56 PM)Sadsilence Wrote: I feel there is also a version with solder tails around. Sorry, no link.

Yes, there is. Here is a version with solder tabs. NiMH cells with low self discharge ("ready to use") and solder tabs generally seem hard to get.

(09-24-2017 05:56 PM)Sadsilence Wrote: Those are LSD cells,

Since not everyone seems to be familiar with this term: this stands for NiMH batteries with extremely Low Self Discharge. This means you can charge them now, put them in a drawer and when you want to use them on Halloween next year (!) they are ready to power your flashlight. Or your calculator. ;-)

(09-24-2017 05:56 PM)Sadsilence Wrote: Of course, contrary to akkuplus (which I can recommend, too) you have to assemble, weld or solder packs by yourself.

That's the essential point. ;-)

Dieter

Hello Dieter,

thanks for additional hints.

Indeed, I have such a welding machine for solder tabs and still looking for 1/3 AAA NiMH LSD cells for my HP82120A packs ;-).

Details of charge curcuit within HP41 rechargeable battery pack are perfectly explained here.

There is a 1/3 AAA NiMH C=170 mAh datasheet from GP, that states an overcharge time of one year for 0.1C charging current (=17mA) does no harm to the cell. Normally, as already mentioned, from overcharging point with high current any energy put into cell is transformed into heat which finally destroys cell's chemistry. A charge current of 17 mA at 1.2V (or 1.4V-1.5V when fully loaded) cell voltage puts so little energy into cell that heating up is neglectable and little heat can easily be dissipated over cell surface.

Looking at HP82120A curcuit actual charging current Ic depends on voltage of cells.
Formula is ( 12V - 0.7V - battery voltage )/ 365 Ohm.

Empty pack @ 4*1V = 4V -> Ic = 12V - 0.7V - 4V / 365 Ohm = 20 mA
Loaded pack @ 4*1.4V = 5.6V -> Ic = 12V - 0.7V - 5.6V / 365 = 15.6 mA

That perfectly matches 17 mA standard charge current of mentioned 170 mAh 1/3 AAA cells.

To get a completely empty battery fully loaded you need around 16 hours (typical formula is 15-16h @ charge current C/10 as there are energy transforming losses). Even if you charge not completely discharged battery for 24 hours there will be no damage. By the way that is exactly the way I charge my rebuilt HP82120A batteries.

Theoratically you can speed up things by replacing 365 Ohm current limiting resistor of charging curcuit with one of lower value. For instance AC wall plug adapter can deliver up to 200 mA or voltage regulator can handle 100 mA or even more. Despite there is more than one reason NOT do it:

1. You can really destroy NiMH cells then.
2. Current limiting resistor gets too hot as power dissipation increases quadratic with current through resistor. Even an 100 Ohm resistor, allowing a current of 60...75 mA is cooked when using a default 0.25W type. Using a high current resistor is no solution due to limited space and capsuled enviroment of battery. There is no way to get heat outside.
3. Voltage limiting Z-Diode cannot deal such high currents in error case and will be blown, too.

Neve · 09-25-2017, 10:43 AM

Hi Dieter,

(09-25-2017 07:36 AM)Dieter Wrote: Re. the 5,8 V 4,94 V thing: this is the first time I hear of a NiMH battery where charging substantially reduces the voltage. That's hard to believe, I'd say there was something wrong with the 5,8 V measurement. But you're the only one how can know. #-)

Charging did not reduce the output, repeated use of the calculator and card reader did. I just can seem to bring it back to it’s original output value of 5.8v. I am positive it was 5.8v. I even checked the next day after extensive use of the card reader and the DVM read 5.0v or 5.1v.

(09-25-2017 07:36 AM)Dieter Wrote: Right. There is not even a rectifier, the output is AC.

Worthy to note that my power adapter specifies an output of 3VA/8V.
I have no way of measuring the current, but the AC output of mine is 12V!
It’s a 82066B Eurocharger.

(09-25-2017 07:36 AM)Dieter Wrote: Yes. You should take a look at this site, also consider the links down the page. But note that there were different versions of the 82120A which may have different electronics inside. Early samples featured a 5 V regulator and other differences (e.g. here), so you have to check what you got!

Although I can’t read German, I can tell you that my battery pack is the one from your first link with the 2-prong outlet. Not the 3-prong one seen on the second link.

Neve · 09-25-2017, 10:48 AM

(09-25-2017 09:50 AM)Sadsilence Wrote: Looking at HP82120A curcuit actual charging current Ic depends on voltage of cells.
Formula is ( 12V - 0.7V - battery voltage )/ 365 Ohm.

Empty pack @ 4*1V = 4V -> Ic = 12V - 0.7V - 4V / 365 Ohm = 20 mA
Loaded pack @ 4*1.4V = 5.6V -> Ic = 12V - 0.7V - 5.6V / 365 = 15.6 mA

That perfectly matches 17 mA standard charge current of mentioned 170 mAh 1/3 AAA cells.

Where do you get your 12V and your other figures? The charger is supposed to be delivering 8VAC (at least that’s what written on it). Although mine does deliver 12VAC!