Keep the batteries in the calc


I am beginning to have a sizeable collection and for the moment I was playing with all my calculators so they all have batteries in. However, I am starting to strugle and it regularly takes me one month to go around all of them.

So now I fear that I may get battery leakage and was wondering if it wouldn't be better to remove all the batteries. Then I realised it may not be a good idea as I may damage some fragile battery covers (28s, Xpander...)

So my question to the user of this museum is: Do you keep the batteries inside your calculators? Why? Why not?




No-no-no, take the batteries off, they will leak

unless, ofcourse, you actually use the calc frequently



What about the capacitors in the calculator? Some capacitors will deteriorate if they don't have voltage applied to them on a regular basis.

I recently saw an example of this. I took a television set out of storage. It hadn't been used for about a year. When I plugged it in, and turned it on, it went berserk. It randomly changed channels on its own, and ignored all of the controls on the front panel and IR commands from the remote control. After about 15 minutes, it settled down and started operating normally.


It *might* also have been a problem of codensation, which, after the TV set became slightly warm, evapourated, or a problem of some components which might have absorbed some humidity... It can happen if some dielcetric material were hygroscopic.
On my side, I would anyway put the batteries out of the calcs...


Did you let settle for overnight first?

Never-ever put on any electric device that has been in cold environment



The television set was stored in an area with regulated temperature and humidity, so temperature changes and condensation were not an issue.

I used to have similar problems with vacuum tube based electronics equipment, like high-fidelity audio amplifiers and FM tuners, that were stored in somebody's attic for years before being sold or given away as junk.

I'm curious about the shelf-life of HP calculators. I have some that are still in their original sealed retail packaging. Will they still work in 10 or 20 years? I know that some plastics out-gas, become brittle, or turn to goo with time. On the other hand, I have a slide rule manufactured in 1935 with no obvious signs of deterioration on its plastic components.


> I'm curious about the shelf-life of HP calculators. I have some that are still in their original sealed retail packaging. Will they still work in 10 or 20 years?

I managed to get an HP-71 for $25 from a surplus store about 15 years after HP quit making the 71. It was absolutely brand-new. Even the lexan overlay around the keys still smelled new. This thing apparently had never had batteries in it except maybe for initial testing at the factory. Everything works perfectly.

Now if I could just get the same insanely low price for duplicates of all the modules I have in my main HP-71, to outfit the second one!


Electrolytic capacitors do deteriorate over time if they are not used. This is particularly true for those with large capacitance values and for those that were manufactured many years ago.

The electrolytics in handheld calculators don't have this problem too often because they're usually quite small in value and not that old (by definition). However this is a common problem in large desktop calculators that use large power supply capacitors. The HP-46 is one calculator in particular that this occurs in. (see:

I try to avoid this problem by running the old desktop calculators in my collect for several hours a month at least.


The small values of electrolytic capacitors generally have much higher voltage ratings than the calculator would need. For example, you'll seldom find a 1µF electrolytic with a WVDC of less than 50V. These will last longer than you will.

OTOH, I worked at TEAC in the early 1980's, repairing semi-professional tape recorders. I found quickly that TEAC had a habit of cutting corners on the larger power supply capacitors, using for example a 16V capacitor for a 16V application, such that they didn't last nearly as long as they should. If they'd go for at least a 25V if not a 35V for the same application, it would never need replacement. A larger capacitance value would also reduce the ripple voltage. All of this means a larger capacitor too, which generally means a lower ESR, which results in less heating and longer life. I guess they didn't care though, as long as it made it through the warranty period.

I have a quarter million parts here in the office for electronic prototyping. As you can guess, some of those are electrolytic capacitors, and most of them have been sitting in the parts bins for 15 years. I use them regularly in prototyping and never have any trouble.

On those rare occasions when I need to use an older, large power supply capacitor, I restore it first by bringing the voltage up on it very slowly, discharging periodically in the process.


Hi Arnaud,

What a nice problem to have - too many calculators - not enough time to play with them all. :)

I'm like you - I really enjoy playing with the calculators much more than just letting them sit on display - actually none of mine are on display.

As to batteries. I'm fortunate to have at least two of each calculator I have. The set of calculators that are in the best condition, I keep the batteries out of them. The set of calculators that are in worst condition I keep batteries in them and they are usually just sitting out where I can easily get my hands on them.

I'm not really concerned if the batteries leak or not. It's more important to me to enjoy them while I can.

So have fun with them, enjoy them, and don't sweat over the small stuff such as battery leakage.



I'm like you - I really enjoy playing with the calculators much more than just letting them sit on display - actually none of mine are on display.

As to batteries. I'm fortunate to have at least two of each calculator I have.

Nearly all my calculators are in my desk drawer at work. Somebody stealing in there could get themselves nice holidays. Unfortunately, I only have one of each (except for a bunch of 45s). So I believe I will just store a few that I don't really use (hp-38g or 28s for instance) and keep a few working that I can check regularly.

I also saw that I store my pioneer and voyager the wrong way up as I read somewhere on this forum that upsise down will avoid dust problem. I will be tidying up on monday. Thank you for your answers.


PS: my only desktop is a 97 which I use regularly so I am not too worried about capacitors.


I believe you should replace all alkalines with silver oxide. Ag batteries last a really long time. Also, if you keep a pioneer face up, but slanted down slightly towards the LCD, tehn if there is a leak, it will drain away from the innards. same goes for the voyagers.

I only buy silver oxide batteries now. The only down side to them is that when they run out of juice, it is very little warning time, relative to an alkaline.

Does anyone know whether Silver Ocide are less (or more) lilely to leak than alkalines?




With the notable exception of the early desktops, none of the capacitors in common hand-held HP calculators are subjected to high ripple currents. In other words, they're not power supply filter caps - they are used to lower supply (battery) impedance and provide continuous memory backup. The real point here is that they never get hot which is what kills aluminum electrolytics. The difference in the two applications (filter vrs bypass) is huge.

The majority of 1uf and larger capacitors in HP calculators are not aluminum electrolytic, they are the more expensive tantalum varieties. The classics with the exception of the 400uf cap in the wall wart are hermetically sealed tantalums - those will no doubt out-live us. Yes, there are some regular old aluminums in our calcs but they are not problematic due to a lack of applied battery voltage.

IMO, the far bigger evil is leaving batteries in units that don't get regular use. Just about all common batteries can and will leak when discharged. I NEVER put cheesy batteries in an HP, why ask for trouble? I've seen plenty of 48's killed by junk dollar store AAA cells. How dumb is that? On the topic of watch cells in the Voyagers and Pioneers - the only cells I've ever seen leak are the el-cheap-o Chinese cells - no doubt alkaline.

Bill's comment is on the money - a calculator stored face up is far less likely to be damaged by leaking electrolyte. But the best way to avoid leaking cells is to just change them on a regular basis - a sticky label with an installation date inside the battery box is very cheap insurance.

Just my two bits worth.

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