Recommendations for storing calculators


Hi all,

After having used a variety of HP calculators for the last 30 years I have just started collecting a few I really liked such as the 41CV & CX, 48GX etc. but as I mainly use my 50G in day to day I was wondering what your recommendations were for storage? I've read some conflicting comments about whether to take the batteries out or leave them :( but any comments/suggestions would be appreciated.




Just use them! :)


I do as much as I can but only 2 hands & eyes available ;).


I'm a school Physics teacher; I bring a different one to work each day! Today it's the 48G+, a late model with a high contrast screen. Tomorrow - who knows?


Remove the batteries, depending on the brand, they will start to leak sooner or later, probably sooner.
Once they have leaked, take care of proper cleaning up the mess - the fluids are highly corrosive and will damage the calculator.


The recommendation to remove the batteries is completely correct. The reason they begin to leak has to do with each of the individual batteries never actually having exactly the electrochemical composition as the others, and so, never have exactly the same amount of stored power. They also all drain at different rates due to the same reason, as well as having been charged at the factory at different times and on different equipment, all which cause ever so slight variances, but enough to cause a problem.

The result is that one or more of the batteries connected in series will eventually drain completely before the others in series, and then that battery will begin to take a negative charge due to being in series with the others which still have some current left. The effect causes the chemicals to become imbalanced and begin to expand and eventually seep out of the vents built into the batteries at the top (+ terminal). Those vents are there to prevent the battery from bursting while being charged or discharged, but they normally only release a gas. Unfortunately when the battery is reverse charged, even ever so slightly, the gas comes off the opposite end of the battery instead, causing reverse pressure in the closed end battery can and forcing the liquid chemical out of the vents at the top. This chemical is usually an Alkaline composition (hence the name Alkaline batteries). It will be highly detrimental to the terminals and can also cause substantial, permanent damage to the circuit board.

The same effect can be caused by accidentally inserting one or more batteries in backwards. ALWAYS observe polarity (+ to - to + to -).

ALWAYS remove batteries if the unit is sitting for more than a few months.

Also, NEVER run on batteries from different appliances. ALWAYS use a BRAND NEW set of batteries from the SAME RETAIL PACKAGE. NEVER MIX USED AND NEW BATTERIES. Finally, when the low battery indicator appears, REPLACE ALL BATTERIES AT THE SAME TIME, AND PROMPTLY, don't wait until they are completely dead, or you may find corrosive chemicals have already leaked out.


Edited: 23 Mar 2009, 12:27 p.m.


To this (leaky batteries) I say you cannot be too careful. I have an HP 49G (yes rubber buttons) that had a cell leak. These batteries were all on the new side and the interesting thing is that the unit still ran without any Lo-Bat indicator active. I believe I checked the stack and found all 3 cells operating within nominal voltage range.



Randy Sloyer from has developed a way to actually repair a calculator that has had leaking battery damage.


There was a discussion on the forum 6 or 8 years ago about my use of AA lithium batteries to power my Classics and Woodstocks and other calculators.

Results to date: All of my calculators still appear to function perfectly when I take them out of the display cases to use them or show them off. To date, no cells have failed or leaked. To date, none of the calculators seemed to be bothered by the little extra voltage.

I will update this again in another 5 years or so...

Has anyone yet seen one of these AA cells leak?


I too have replaced all the nicads in virtually all my HP and non-HP calculators with AAA or AA lithium cells several years ago For the HP calculators that use 3 AA nicad cells in a pack I used a modified 3xAAA plastic holder and loaded it with primary lithium cells. Similarly for those that have 4 sub-C nicad cells in a pack I used a modified 4xAAA plastic holder and loaded it with primary lithium cells. I have around 250 calculators that I've done this for using various AA and AAA cell holders with Energizer lithium cells. None and leaked and no calculator has been damaged (by the higher voltage).


Dr Meyer; Your calculators might appear to function normally and may not seem to be bothered by the excess voltage. However; they could be sublimating their desires or repressing their emotions. How do they really feel?

But seriously: what a great idea. I looked them up and not only aa and aaa sizes are available but 9v and N cells too. That would take care of my 48 & 41 series, a couple of Novus/Nat Semis and their clones, the Corvus & it's clones, a few of the Ruskies and the Privilegs. Most of my toys really. The only problem is that i have already invested in rechargeables and the chargers for those - and i'm cheap. BTW: the charger and deep cycler for the N cells work because Katie told me how to build them.


Are you talking about 1.5V Lithium N cells? Where did you find them? I've only seen lithium iron disulfide (1.5V) in AA and AAA.

The lithium 9V batteries I've seen contained three 3V cells, most likely lithium manganese dioxide.

I'm tempted to make a rechargeable lithium-polymer battery pack for my 41. It would require either a boost regulator (for one cell) or a buck regulator (for two cells). A buck regulator with burst mode should be very efficient. Without a card reader, it should power the 41 for quite a long time between charges (much better than the 82120A).

Has anyone measured the peak current draw of the card reader?


Eric; These are all i found.

BTW:Since people were talking about historic lithium cells, here's my "golden age of batteries" memory. Back in about '78 a climbing buddy who we had nicknamed "REI" got a new toy. It was an MSR headlamp, with a twist. The designer, Larry Penburthy, supplied it with Lithium cells and 4 bulbs of increasing sensitivity that were easily changed. Since the batteries had such a flat discharge rate; when your lamp got dim you'd just pop in the next bulb in the series. One set of batteries would last an incredible (but now forgotten) amount of time and that weight one saved by not carrying multiple sets of cheap alkalins mattered when you were dragging it, and all your wet clothing & gear, up 8000 feet in the Seattle rain. That man had the best toys.
I still have my MSR G type stove, bivi sack, locking beaner and Thunderbird ice axe. They'll outlive me.



This ad is mistaken, they are alkaline N cells. Energizer doesn't make lithium N cells and as far as I know no one else does either.


I've searched "high & low" but can't finf Lithium N size batteries for my HP41C's. Do any of you have a link or recommended supplier you have come across?




What voltage rating AA's are you using? Certainly if you use the 1.5 V ones, you won't have any problems with potential harm to your calculators. The calculator voltage rating is a minimum value under load for proper functioning of the calculator and the maximum safe value is much higher. The no-load DC voltage output of a classic charger on the calculator adapter side is over 5 V, whereas a charged NiCad pack will be between 4 V and 4.5 V, and the rating on the calculator back label is only 3.75 V. So, assuming that a new AA Lithium will show maybe 1.7 V no load voltage, 3 x 1.7 = 5.1 V will not hurt your calculator. I've experimented with an old beat up HP-45 (I have 7 of these suckers so I can afford to torture one of them) by hooking it up to my DC power supply, and ran it for a week non-stop with all LEDs lit with a constant 6 Vdc input, and nothing burned up. I do like your idea of using Lithium AA's for calcs that normally would use alkalines, but still like to use traditional NiCad battery packs in my classics and other LED models that normally use them. I never leave the packs installed, except when I'm actively using them.



to my knowledge, these are usually marketed with "10 years lifetime", so one could assume they are built to last that long :)
Btw. I have one calculator (Datamath), that still has the original NiCd-cells installed - they still look like new, no signs of leakage at all. I assume they have never been charged.


My own personal experience with NiCads is that the have an almost indefinite shelf life if they remain new and uncharged. I have several National Semiconductor LED caculators which I bought completely new and unused in the box with built-in NiCads, and I was able to initially charge all of them fully. However, they only lasted a very few charge cycles, and then went bad. Two of them then began to leak badly. It was at that point that I removed them and replaced them with new NiCads. Also, I have seen several very old (over 20 years) HP battery packs that seemed to work perfectly and were not leaking even after many charging cycles. So I think maybe not all NiCads are created equal.


My own personal experience with NiCads is that the have an almost indefinite shelf life if they remain new and uncharged ... I think maybe not all NiCads are created equal.

I agree with the last statement, but my experience is not the same as indicated in the first. I have collected and used Nikon F2 series cameras for about 28 years. Nikon is arguably Japan's most respected camera manufacturer. In seeking out various pieces years ago, I found that brand new NiCads that had been on the dealers shelves for 10+ years simply would not hold a charge. Once I figured this out, I just had my own new ones built up, or in some cases adapted cordless phone batteries myself. (Of course Nikon did not make their own NiCads, usually obtaining them from Yuasa).

I have also purchased NOS EverReady NiCad C cells that would not hold a charge.


Where would HP calcs fall on this timeline?? Just before RC Planes?


XKCD is one of my guilty pleasures too. I don't know if the writer reads us but i found this on the KXCD forum:

The HP50g is absolutely godlike and I take comfort in the complete superiority it represents. It is the pinnacle of engineering, art, Western thought and human kind. The engineers at HP plucked it and its included faux-leather carrying case from the realm of the gods, and in so doing gave physical form to the Platonic ideal of the calculator. Its 9.5 megabyte, 887 page user's guide was penned by monks and inspired by a choir of heavenly muses. All hail the glorious HP50g.

Imagine how he would gush if he used a 41.


Surely Cyrille has also read this glowing (perhaps overly so) review of the 50g. Not that I disagree, but perhaps the XKCD author could humor us with a comic on HP calculators :-) (since as the XKCD Warning states: this HP museum forum occasionally contains strong language (which may be unsuitable for children), unusual humor (which may be unsuitable for adults), and advanced mathematics (which may be unsuitable for liberal-arts majors)


Chuck, were all these batteries installed from a fresh pack and all at the same time? If not, even if all the batteries appear to be "in the normal range", if they are not nearly identical in voltage, the increased current through the on lowest voltage battery will cause it to heat up and if it does heat beyond the normal "gas leak" range, some of the Alkaline fluids can leak causing the problem you had.

As far as Lithium batteries, I have never seen one leak, nor heard of one leaking. I believe it is because they are essentially "dry cells", where the Lithium between the Anode and Cathode (Negative & Positive), is of a dry solid composition (actually a Lithium salt disolved in an organic solvent, but drier than an Alkaline battery). Also, if it did leak, I believe the PH of the solvent would not be Alkaline and so would not cause corrosion, but I could be wrong.

See below;
"The latest non-rechargeable lithium batteries utilize an even newer chemistry, that delivers dramatically higher energy capacity than even the very best of alkaline batteries. The operating lives (run times) of lithium batteries will often be two to six times that of the same sizes of alkaline batteries, depending upon the drain rate and usage cycling of the application. And the disposable lithium batteries provide amazing typical initial
shelf lives of ten years (and up to fifteen years for certain types), depending on quality.

Lithium batteries also weigh less and tolerate temperature extremes better than most other types, but they usually cost much more, and can become hazardous if damaged. Because of their extraordinary storage lifespans, and because most have a built-in vent to relieve any buildup of gasses, leakages of disposable lithium batteries are relatively rare, unless they are mishandled or improperly installed. So the remainder of this article will address the lower cost carbon and alkaline battery types, which will leak very readily.

When carbon or alkaline batteries have become discharged, the chemistry of the cells will degrade and some hydrogen gas will be generated. This out-gassing will result in increasing pressure within the battery. Eventually, the excess pressure will either rupture the insulating seals at the end of the battery, or bulge and rupture the outer metal canister, or both. When this happens, an acidic (for carbon cells) or caustic (for alkaline cells) electrolyte gel will ooze from the battery. In addition, as the battery ages, its zinc (for carbon cells) or steel (for alkaline cells) outer canister may gradually corrode or rust, and this can further contribute to leakage failure. Extremely high temperatures,
such as those in the vehicle glove box during the summer, can also cause batteries to rupture and leak, even when they are relatively new.

The leaking electrolyte can corrode the metal housing and battery contacts of a simple flashlight, and it can damage or destroy the delicate circuitry of an expensive electronic flashlight. Furthermore, swelling of the battery canisters can render one or more of the batteries hopelessly jammed within the flashlight body. One leaking battery can cause a chain failure, when its leaking goo corrodes the adjacent ones so that they then leak.
A five dollar set of dead batteries can and will destroy a five hundred dollar instrument if you let them. Countless numbers of otherwise perfectly fine flashlights are discarded every year due to battery leaks. Only you can prevent the tragedy of death by leakage.

The most important thing to remember is this: dead batteries will eventually leak. And all batteries will gradually self-discharge (even if they are not operating the device they are installed in, and even when they not installed at all but just sitting on a shelf or in a drawer, they will slowly lose energy capacity over the passing of time). So, no matter how good the brand name, your batteries will eventually go dead even if you don't use them, and when they go dead they will eventually leak. These simple facts lead to just three easy rules, which must be followed without exception to protect your investment in flashlights and other battery-operated equipment.

Always remove dead batteries immediately - All dead batteries are subject to very rapid leakage. When the batteries can no longer
effectively power the device, remove them at once and take them to a recycling center. If the device has several batteries, always replace every one of them at the same time.

Remove batteries when equipment is stored - Whenever a given device will not be used for any extended period of time (one month or more), remove and properly store its batteries. In extreme conditions, such as the car glove box in the summer in hotter climates, install the batteries only when needed.

Properly store and dispose of your batteries - Store uninstalled batteries in resealable plastic bags or battery carrier boxes, so that if they leak they will not damage nearby items. Check them every month or so for any swelling or leakage. Do not throw away weak or aging batteries, and do not just toss them into a drawer, but instead take them to a nearby battery store or recycling center
for proper disposal. Note that some states and municipalities now mandate recycling for all consumer battery types. Please help to reduce the environmental impact of the billions of batteries that expire each year, recycle them as if your future depends on it.

So what do you do if some batteries have already leaked and ruined your flashlight or other device? Some technicians will tell you that you can wet a toothbrush or a cotton swab with a solution of baking soda, and scrub away the acidic goo and crust from a
leakage caused by carbon / zinc batteries. Or similarly, apply a solution of household vinegar to scrub away the residues from a leakage caused by alkaline batteries.

This may actually work in some instances, but the cleaning solution could damage the delicate electronics in sophisticated flashlights or items such as radios and tape players. And while you may be able to open both ends on some flashlights to push out swollen batteries, some flashlights can only be opened from one end such that you cannot dislodge batteries that have become jammed due to swelling."



I wanted to add a note to this fine post on energy cells.

Some suggest dissolving baking soda in, or adding vinegar to, water for the purpose of cleaning up spilled electrolyte. I have found that this is rarely, if ever, the best course of action.

Pure water, distilled if you have it handy, works best. Vinegar is an acid, and baking soda is alkaline, so the 'clean-up' that you do could further damage the device you are cleaning. Whereas 'a bit of the hair of the dog' might work for your Sunday morning hangover, it won't help your precious calculator.

All electrolyte spills I have cleaned up are readily dissolvable in pure water. A good cleaning with water will remove all acid and alkali from the device. And in the absence of an electric potential (i.e. batteries and power supply removed), pure water is not corrosive (unlike vinegar and baking soda). Just make sure it is completely dry before adding batteries or power to the device after cleaning.



Thanks for the question, these batteries were all from the same pack, and as I said the unit was still operating. These batteries were all fairly new, I believe I had installed them a few months earlier and it is in a calculator I don't use on a regular basis.



Hi all,

Thanks for the excellent responses. Simplest solution seems to be to switch over to Lithium batteries so I will try & locate the size N, AAA's etc. I need.



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