HP-41 Batteries
11-25-2014, 11:51 PM
Post: #1
 klacombe Junior Member Posts: 12 Joined: Nov 2014
HP-41 Batteries
I have been searching the forum and elsewhere for a concensus on what people are using for batteries in the HP-41. I have a few dead rechargeables that I would like to rebuild and am in the process of doing that to one pack with 1/3AAA NiMH cells. I found a link on ***** for rebuilding with 2/3AAA cells and using a DC adapter to charge the pack. Any one have experience rebuilding packs in any fashion? and if so what were the results? Any other setups used? I have some rechargeable N cells that I can get charged in a charger but I can't seem to get to work in the 41. The button is very small on the positive side. Outside of that, I'm just using Energizer alkalines. Is there any chance there is a "rebuilding batteries" chapter or appendix in the upcoming book Geoff? -Kevin
11-26-2014, 07:37 AM
Post: #2
 Geoff Quickfall Senior Member Posts: 733 Joined: Dec 2013
RE: HP-41 Batteries
Hi Kevin

There are some eBay sales involving the 1/3 AAA and I have some raw batteries on the way. They are the correct length and diameter to be a natural direct replacement but I will let you know in about a week.

Yes, there is an appendix dedicated to all batterie pack rebuilds.

Cheers, Geoff
11-26-2014, 04:17 PM
Post: #3
 klacombe Junior Member Posts: 12 Joined: Nov 2014
RE: HP-41 Batteries
Thanks Geoff, I'm sure I'm one of many (im)patiently waiting for your book release. One of the sources for cells (both 1/3AAA and 2/3AAA) that I found is Pololu. They sell pre-soldered packs for use in things like RC vehicles. Much cheaper than buying individual tabbed cells and most of the work is already done for you. They do not have the set of 4 1/3AAA in stock so I went with 2 sets of 6 cells and was able to create 2 sets of 4. Connected, mine charge in the pack with the standard AC adapter but I'm not happy with the fit so I am looking at other options. They are a hair longer than the original 1/2N cells which makes for a tight fit with the two spring loaded contacts!
11-26-2014, 09:32 PM
Post: #4
 Garth Wilson Senior Member Posts: 387 Joined: Dec 2013
RE: HP-41 Batteries
I'm not quick to recommend rechargeable batteries for the 41 unless you're using the card reader or the bar-code reader wand a lot. My own 41cx went two years on each set of alkalines even with everyday use, until I got a double extended memory module which seems to have more leakage current and took the battery life down to around six months on a set of alkalines, again with everyday use. If you use rechargeables, you'll have to have two sets if you have to remove one set to put it in the charger, using the second set to preserve the memory while the other set is getting charged. The price of two sets of rechargeables plus charger will buy many, many years' worth of alkalines, and the rechargeables need more-frequent attention because of their self-discharge rate. Yet another point is that if the rechargeables are 1.2V, my own 41 would show the low-battery annunciator all the time, because it comes on at 1.2V. Again, I don't recommend rechargeables unless you often use the card reader or the bar-code wand. I have the tape drive, but I have enough memory in my 41 to perpetually keep everything I need in it, so I virtually never have to access any kind of external storage.

11-26-2014, 09:36 PM
Post: #5
 Geoff Quickfall Senior Member Posts: 733 Joined: Dec 2013
RE: HP-41 Batteries
I agree Garth,

However, repurposing the rechargeable 41c pack is the purpose. It then takes the standard HP double pronged adapter which recharges it saving the cost of an external charger.

Besides, if can be done and look original, then why not?

The rechargeable 41c battery pack contains all the electronics and plugs for charging, in a neat battery pack. Quite exquisite. Also, with NiMH you get a good mah capacity.

Cheers, Geoff
11-26-2014, 11:12 PM
Post: #6
 Garth Wilson Senior Member Posts: 387 Joined: Dec 2013
RE: HP-41 Batteries
Quote:then why not?

Perhaps with the exception of Enlode batteries which have a very low self-discharge rate, you have to keep charging it, even if you hardly use it. You cannot go months or years without paying any attention to the batteries like you can with alkalines. Obviously it's each user's choice, but for myself, I don't want to be bothered with it.

11-27-2014, 12:47 AM
Post: #7
 klacombe Junior Member Posts: 12 Joined: Nov 2014
RE: HP-41 Batteries
Yes, I am venturing into card reading and barcoding. I just paid less than a $1 a piece for energizers but I guess it's more about seeing if I can than cost. I agree that the voltage is an issue but still the same issue as with the original rechargeable pack. With the use of NiMH batteries it gets a little better and repeated charging is less of a problem. I am very interested in trying the use of 2/3AAA rechargeable batteries as documented on Warren Furlow's site with a DC adapter. I was actually curious if anyone had tried that size directly in the normal battery carrier. I suspect you would need to fatten them up a little (10mm dia compared to 11.68mm). I would consider using those because you can readily get those in NiMH with the standard ends. Easily charged in a standard charger as well. 11-30-2014, 01:17 AM (This post was last modified: 11-30-2014 01:18 AM by Joe Horn.) Post: #8  Joe Horn Senior Member Posts: 1,612 Joined: Dec 2013 RE: HP-41 Batteries Although too long to fit the HP 41 rechargeable battery pack, I use full-size NiMH N cells with great success. For some obscure reason they last longer than alkalines in my CX. Here's one source for them... a real bargain at just two bucks each. One of the reviewers there even mentions the HP-41! EDIT: Here's another source, at$1.75 each.

<0|ɸ|0>
-Joe-
11-30-2014, 02:04 AM
Post: #9
 klacombe Junior Member Posts: 12 Joined: Nov 2014
RE: HP-41 Batteries
Thanks Joe,

I also found these:

http://ogazent.com/cscart/index.php?disp...duct_id=13

They list some adapters for charging but are out of stock:

http://ogazent.com/cscart/index.php?disp...duct_id=14

What do you do to charge the cells? I have a nice Panasonic charger that came with envelop AA and AAA and it seems like they would charge N cells. Just not sure what to use to adapt for the size and how long to charge. -Kevin
11-30-2014, 02:21 AM (This post was last modified: 12-01-2014 01:00 PM by RMollov.)
Post: #10
 RMollov Member Posts: 245 Joined: Dec 2013
RE: HP-41 Batteries
(11-25-2014 11:51 PM)klacombe Wrote:  I have been searching the forum and elsewhere for a concensus on what people are using for batteries in the HP-41. I have a few dead rechargeables that I would like to rebuild and am in the process of doing that to one pack with 1/3AAA NiMH cells. I found a link on ***** for rebuilding with 2/3AAA cells and using a DC adapter to charge the pack. Any one have experience rebuilding packs in any fashion? and if so what were the results? Any other setups used? I have some rechargeable N cells that I can get charged in a charger but I can't seem to get to work in the 41. The button is very small on the positive side. Outside of that, I'm just using Energizer alkalines. Is there any chance there is a "rebuilding batteries" chapter or appendix in the upcoming book Geoff? -Kevin

I use alkaline 'N' size - overpriced, but (still) readily available. Calculator only (no peripherals) gets more than a year life out of them. In my experience rechargeables are waste of time and money.
11-30-2014, 05:38 AM
Post: #11
 Dave Frederickson Senior Member Posts: 1,749 Joined: Dec 2013
RE: HP-41 Batteries
(11-30-2014 02:04 AM)klacombe Wrote:  Thanks Joe,

I also found these:

http://ogazent.com/cscart/index.php?disp...duct_id=13

They list some adapters for charging but are out of stock:

http://ogazent.com/cscart/index.php?disp...duct_id=14

What do you do to charge the cells? I have a nice Panasonic charger that came with envelop AA and AAA and it seems like they would charge N cells. Just not sure what to use to adapt for the size and how long to charge. -Kevin

I bought some of these N-cell adapters earlier this year. Email customer service and ask them to make some more. I use a BC-700 charger.
11-30-2014, 01:44 PM
Post: #12
 Joe Horn Senior Member Posts: 1,612 Joined: Dec 2013
RE: HP-41 Batteries
(11-30-2014 02:04 AM)klacombe Wrote:  What do you do to charge the cells? I have a nice Panasonic charger that came with envelop AA and AAA and it seems like they would charge N cells. Just not sure what to use to adapt for the size and how long to charge. -Kevin

Any "smart" recharger works fine, using magnets to provide contact. Obvious but I'll say it anyway: Do NOT use "trickle" rechargers which either never turn off, or merely time out. Spend the few extra bucks for a smart charger. Then you'll never have to worry about how long to recharge.

<0|ɸ|0>
-Joe-
11-30-2014, 03:14 PM (This post was last modified: 12-04-2014 07:50 PM by Dieter.)
Post: #13
 Dieter Senior Member Posts: 2,397 Joined: Dec 2013
RE: HP-41 Batteries
(11-30-2014 01:44 PM)Joe Horn Wrote:  Any "smart" recharger works fine, using magnets to provide contact.

I agree that an intelligent charger is mandatory since it works fast and protects the batteries against overcharge and other problems. On the other hand not "any smart recharger" can be recommended. Assuming a typical NiMH N-size cell capacity of 400-500 mAh and a limit of 0.5 CA, the charging current should not exceed 200 mA, preferably 150 mA. Most intelligent chargers are designed for AA and AAA batteries with much higher capacity and thus they provide much higher charging currents. Some better chargers can be set to suitable lower currents, e.g. the well-know BC700 with a default setting of 200 mA. So an empty 400 mAh N-cell will be charged in about 2.5 hours.

Regarding the other option of replacing the old cells in a HP 82120A battery pack with current NiMHs, using the original HP charger (82066A, 82059A etc.): I asked my local battery supplier and ordererd a custom made pack of four 1/3 AAA (or 1/2 N) cells, professionally welded and ready to be used in the original (empty) battery pack. Most battery refurbishment/rebuilding services should be able to do this.

However, using regular N-size NiMHs in a standard HP41 battery holder and charging these in a decent processor controlled external charger technically is the better option. It provides much more capacity, decent charge control – and it requires no soldering or other inconveniences. ;-)

Dieter
11-30-2014, 05:54 PM (This post was last modified: 11-30-2014 05:55 PM by Geoff Quickfall.)
Post: #14
 Geoff Quickfall Senior Member Posts: 733 Joined: Dec 2013
RE: HP-41 Batteries
All great ideas,

Let's sum up:

-Alkaline N cells are readily available, last a really long time ( my goto battery),

-NiCd N cells harder to find but we're my choice 30 years ago for the 41c. Had a charger with bracket holders for N cells. Joes magnet idea, great!

-NiMH N cells better option then NiCd.

-From a collectors standpoint, a rechargeable battery pack with 1/3 AAA * 4 is a nice option, again, from a collectable standpoint. Saves the need to find a separate recharger and allows for the use of the HP adapter.

IN reality, for the office I have a 41cl with two battery packs contains alkaline N cells. One ready to go for the quick swap!

Cheers, geoff
12-02-2014, 07:35 PM
Post: #15
 klacombe Junior Member Posts: 12 Joined: Nov 2014
RE: HP-41 Batteries
Thanks Dave, I got a response from Ogaz and was able to order 4 of the adapters and 12 batteries. They are out of the adapters but are making more if anyone's interested. -Kevin
12-02-2014, 08:00 PM (This post was last modified: 12-02-2014 08:05 PM by Dieter.)
Post: #16
 Dieter Senior Member Posts: 2,397 Joined: Dec 2013
RE: HP-41 Batteries
(12-02-2014 07:35 PM)klacombe Wrote:  Thanks Dave, I got a response from Ogaz and was able to order 4 of the adapters and 12 batteries. They are out of the adapters but are making more if anyone's interested.

Real cowboys make their own adapters: Take a look at the picture in this message in the old forum. ;-)
That thread also contains some other useful information.

Dieter
12-02-2014, 08:40 PM
Post: #17
 Dave Frederickson Senior Member Posts: 1,749 Joined: Dec 2013
RE: HP-41 Batteries
(12-02-2014 08:00 PM)Dieter Wrote:
(12-02-2014 07:35 PM)klacombe Wrote:  Thanks Dave, I got a response from Ogaz and was able to order 4 of the adapters and 12 batteries. They are out of the adapters but are making more if anyone's interested.

Real cowboys make their own adapters

Aww, man, that's harsh. There wasn't room for a lathe on my horsie as the space was taken up by my soldering iron.
12-02-2014, 10:02 PM
Post: #18
 klacombe Junior Member Posts: 12 Joined: Nov 2014
RE: HP-41 Batteries
Thanks Dieter,

I agree, I'm just not sure I could even buy the aluminum for what the adapters cost. I had been looking through the forum archive but hadn't gotten to #20 yet. Learning as I go I guess? Thanks again for the link. -Kevin
03-01-2015, 04:06 AM
Post: #19
 TASP Senior Member Posts: 401 Joined: Mar 2015
RE: HP-41 Batteries
I'm anticipating using a card reader on a 41CX soon. I have an old NiCd era stand alone N-cell charger.

Do the NiMH batteries have the same 'knee' effect on the voltage the NiCds had ?

It can mess up the card reader if the 'knee' occurs during an operation, for those who recall such minutiae.

2speed HP41CX,int2XMEM+ZEN, HPIL+DEVEL, HPIL+X/IO, I/R, 82143, 82163, 82162 -25,35,45,55,65,67,70,80
03-01-2015, 01:37 PM
Post: #20
 Dieter Senior Member Posts: 2,397 Joined: Dec 2013
RE: HP-41 Batteries
(03-01-2015 04:06 AM)TASP Wrote:  Do the NiMH batteries have the same 'knee' effect on the voltage the NiCds had ?

I am not sure what you mean here. If you refer to a more or less sudden voltage drop before the batteries are exhausted: yes, that's essentially the same with NiNHs.

(03-01-2015 04:06 AM)TASP Wrote:  It can mess up the card reader if the 'knee' occurs during an operation, for those who recall such minutiae.

You may want to take a look at the manual. The 82104A card reader has several means to handle low batteries. If the voltage drops while a card is read, the motor switches to intermittent operation. It is turned off and on for fractions of a second until the card has passed through the reader. A low battery message appears in the display (not just the usual BAT annunciator). If the batteries are completely exhausted and the card gets stuck in the reader, simply disconnect it, install a fresh set of batteries and re-attach the reader. The card will then complete its travel.

BTW, what kind of dedicated N-Charger are you planning to use? What is its charging current and what kind of charge control does it use?

Dieter
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