Which batteries for 41CV?

[HP67]

I never had the chance to use one of these and I have been wanting one for a while... so I finally bought one on fleabay. It has not arrived yet.

Do these work with regular batteries? It looks from the pics on TAS people are using standard AA or AAA (didn't see which) but sites seem to say N Alkaline.

Thanks.

[Maximilian Hohmann]

Hello1

(10-16-2018 07:06 PM)HP67 Wrote:  Do these work with regular batteries? It looks from the pics on TAS people are using standard AA or AAA (didn't see which) but sites seem to say N Alkaline.

The only cells that fit physically are „N“ cells. There are alkaline or rechargeable (NiCd I guess) types, the latter ones very, very difficult to find. And you will need a charger for them as well.

Regards
Max

[HP67]

Thanks. Ok, looks affordable on TAS. How long does a set last in a 41CV used for an hour or two a day desk duty and programming? Ballpark number just to give me a general idea would be appreciated. Thank you!

[KF6GPE]

It's been a while since I used mine in any real capacity (I've switched to a DM41L) but if memory serves at least a handful of weeks, unless you've gone nuts and gotten a card reader or HP-IL peripherals or something.

Have fun with that calculator. It's a great machine.

[Maximilian Hohmann]

(10-16-2018 07:20 PM)HP67 Wrote:  How long does a set last in a 41CV used for an hour or two a day desk duty and programming?

Could be up to a year I guess.

[HP67]

Thanks a lot for the help.

[Massimo Gnerucci]

(10-16-2018 07:12 PM)Maximilian Hohmann Wrote:  The only cells that fit physically are „N“ cells. There are alkaline or rechargeable (NiCd I guess) types, the latter ones very, very difficult to find. And you will need a charger for them as well.

Also NiMh are available, and not so difficult to find, Maximilian.
You can use a common charger (usual recommendations for a BC-700 apply here too) with adapters.

[Garth Wilson]

(10-16-2018 07:20 PM)HP67 Wrote:  Thanks. Ok, looks affordable on TAS. How long does a set last in a 41CV used for an hour or two a day desk duty and programming? Ballpark number just to give me a general idea would be appreciated. Thank you!

I originally got my 41cx in 1986 for controlling equipment on the workbench at work through HPIL and the HP82169A HPIL-to-IEEE488 interface converter. It actually ran an automated test setup for production for the first year or so, getting used many hours each day, and a set of alkaline batteries lasted a couple of months IIRC. I suspect the calculator is basically idling when it's waiting for readings to come back from the equipment. After the control was transferred to a 68000-based HP9000-series computer, I kept using the HP-41cx daily, but not constantly, and a set of batteries lasted a couple of years. After eBay came into being, I got a double extended memory module, and battery life dropped to six months. A year ago I got a Clonix-D module and put several ROM module images in it, and battery life now is down to ten weeks. I get 20 N cells at a time on eBay for $0.85 each, including shipping, which is a lot cheaper than Radio Shack used to be!

[Maximilian Hohmann]

Hello!

(10-16-2018 07:44 PM)Massimo Gnerucci Wrote:  Also NiMh are available, and not so difficult to find, Maximilian.

Yes, you are right. It's been some time since I last shopped for N cells... I usually get them by buying calculators which already have some inside ;-) This is also how I got my 4 rechargeable ones.

I did a quick research and if one looks for either "Lady" or "LR1" batteries instead of "N cell" there are far more search results. The recharcheable ones seem to be commonly used in LED bicycle tail lights (and also sex toys, that's maybe why they call them "Lady" cells around here...) so they might even be on store in a nearby bicycle shop.

Regards
Max

[HP67]

Thank you guys for the additional info on time and also about the rechargeables. I didn't know what to search for, I'll look for LR1. Seems like these are used as alarm batteries so maybe there is a charger available too.

[burkhard]

(10-17-2018 05:15 PM)HP67 Wrote:  Thank you guys for the additional info on time and also about the rechargeables. I didn't know what to search for, I'll look for LR1. Seems like these are used as alarm batteries so maybe there is a charger available too.

Let us know if you find a dedicated charger. It baffles me that the rechargeable N / LR1 are not impossible to find, but in order to charge them you have to jury-rig something to put them in a AAA charger. I'll probably just do this, though. It does concern me that the minimum 200mA charging rate in my ubiquitous BC-700 charger is probably too high for the smaller N, but "oh well".

[John Keith]

If you live in North America this is a good source:

https://www.digikey.com/product-detail/e...-ND/704824

Unfortunately they do not list any rechargeable N cells.

[ijabbott]

The phrase "lr1 rechargeable" gets some hits on Amazon.com and Amazon.co.uk.

[Steve Simpkin]

Also be aware that there is an "A23" battery that is about the same size as an "N" battery but puts out 12V instead of 1.5V. Obviously do NOT use an A23 battery in your HP-28. There have been several cases where someone has destroyed their HP-28/HP-19 Clamshell calculator by using these instead of "N" cells.
https://en.wikipedia.org/wiki/N_battery

[Zaphod]

(10-17-2018 06:53 PM)Steve Simpkin Wrote:  Also be aware that there is an "A23" battery that is about the same size as an "N" battery but puts out 12V instead of 1.5V. Obviously do NOT use an A23 battery in your HP-28. There have been several cases where someone has destroyed their HP-28/HP-19 Clamshell calculator by using these instead of "N" cells.
https://en.wikipedia.org/wiki/N_battery

It’ll rattle in the holder (hopefully... 10.3mm vs 12mm dia) and a tiny bit shorter (~2mm)
But never underestimate the ability for a human to force something in

[HP67]

Thanks guys, apparently the LR1 is an alkaline rather than rechargeable. I have a 12 pack of Duracell E90s coming which ought to be good to start with.

I am in Europe but I think we have digikey or mouser local sites. The only problem is they usually have a minimum purchase of 50 Euros. I've been meaning to get some other goodies, so...!

Horrible about destroying calculators with the wrong batteries.. I will certainly read the fine print before I put anything in the battery holder.

I didn't find a dedicated charger after all but I'll keep an eye open for sources of rechargeables and chargers. I guess it wouldn't be too difficult to put together a charger for cheap using a 4xAA battery holder with long springs or shims of some kind.

Thank you!

[Zaphod]

Quote:in europe

https://www.batteriesplus.co.uk/acatalog...gJYBPD_BwE

[Didier Lachieze]

In Europe you can buy the rechargeable batteries, the AA adapters and the appropriate charger here

[burkhard]

(10-17-2018 07:42 PM)Didier Lachieze Wrote:  In Europe you can buy the rechargeable batteries, the AA adapters and the appropriate charger here

That's excellent. I need to find some of those adapters on the US eBay. I'm sure somebody in Red China sells a set of 4 for $1.50 postage paid, but I don't see them.

In your link from Akkushop, it does show the rechargeable N cells have a 500 mA·hr capacity, but the BC700 style charger has a minimum setting of 200 mA charging current. Isn't the rule-of-thumb that the charging current (in mA) should be limited to about 1/10 the nominal battery capacity (in mA·hr)? If so, it's about 4× higher than optimal. Has anyone had any "troubles" from charging the N cells this hard? The page directs you to use 200 mA and not the 500 or 700 mA settings, but even 200 seems pretty high to me for these little cells.

[John Keith]

(10-17-2018 08:23 PM)burkhard Wrote:  Isn't the rule-of-thumb that the charging current (in mA) should be limited to about 1/10 the nominal battery capacity (in mA·hr)? If so, it's about 4× higher than optimal. Has anyone had any "troubles" from charging the N cells this hard? The page directs you to use 200 mA and not the 500 or 700 mA settings, but even 200 seems pretty high to me for these little cells.

That rule of thumb applies to constant current charging of NiCd cells. "Smart" NiMH chargers typically use higher current initially, then taper down to a trickle charge once the circuit detects that the cell is fully charged.