HP 33E Programable Calculator


I have discovered an HP 33E Programable Calculator in my store room. It is complete with Owners Manual and power supply for recharging the batteries I assume but it seems to be defective. Unfortunately the battery pack is also missing. I would dearly love to get this calculator operational again as I prefer working in RPN and really loved the HP RPN calculators. Can anyone please tel me what the 33E Battery voltage was and in the battery compartment which terminal is +ve. There is no indication in the battery compartment. I assume that the battery pack was so designed that it could only be inserted with terminals in the correct position. Are there any of these batteries still available? Assistence in getting this fine calculator operational will be sincerely appreciated.
Willem 13 May 2005


Original HP batteries are no longer available. They were very similar to a standard AA nicad, just a bit shorter. Any regular AA nicads (600-1200mah) work fine. It is best to buy a fabricated pack - two cells with a strap welded on the right side to connect the two.

The topmost left terminal is (-), the bottom (+).

If you're in the US, see http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=335 for a source for fabricated packs.


Hi, Randy;

just to make sure about battery polarity: when you mention the topmost, you mean the battery that's closer to the one that's handling the calculator, right? When I first read your post, I thought it was the opposite, because when you are looking at the terminals from the back of the calculator, the topmost may also mean the one in the upper position, closer to the LED display, that is, in this case, the negative pole.

Maybe this is because I'm no native English speaker, so please, forgive me if I confused your explanation. I was mainly affraid of having the batteries installed with the wrong polarity.

Best regards.

Luiz (Brazil)

Edited: 12 May 2005, 8:16 p.m.


Don't worry Luiz, we all speak the same language, RPN don't we? LOL




Just use 2 x 1.5v alkaline batteries. I'm using the same thing as I write this. A nice unit if you have it. The positive terminal is right top and bottom left if you have the calc facing you mormally and you turn it backwards with the battery compartment at the top. Just make sure you connect the right side of the batteries with something metallic. I used aluminium foil and it works like a charm
I'm sure there are better ways but I use the unit for around 1 hr a day and they last about 4-5 months. Not bad I think

Good luck



Hi, Paul;

I use a pair of rechargeables, and a small, flat piece of metal to connect them both. In fact, it's a cut from old 9V alkaline batterie...

The rechargeables avoid having to open the battery door to replace the batteries (I'm always affraid of breaking it when openning...), and the new rechargeables do not leak as easy as it used to happen to some of the eariler ones.

I tested a few different brands, either NiCad or NiMH, from 700mAh (currently in two HP38C) to 1700mAh (currently in my HP34C), and despite of the different discharging time, they work pretty fine, no complaints at all. I tested Panasonic NiCads of 850mAh, 1100mAh and NiMH 1600mAh, GP (Gamma Power) NiCad 700 and NiMH 1700mAh, all of them worked fine. I know that based on current consumption and estimated discharging time, one can 'predict' how long will a fully charged battery maintain a Spice working with a running program or simply with "led's on" stand by, but I'm not sure about how to use this information. I just wait till the 'low power' dot to come up so I plug the charger in. What I'd actualy like to know is how long should I wait till the more powerfull batteries are fully charged.

I once posted about this here, and I am aware of the fact that a battery with more miliamps (capacity) needs more time or a higher constant current to be fully charged. I also know (at least I think so) that the recomended charging current in most cases is about 10% the nominal battery current, so the Spices have their mains supply designed to charge their orignal rechargeables that are, IIRC, about 500mAh. If we take proportionaly, the 1600 mAh would need about 30 to 36 hours for a full-charge operation if charged by the original Spice circuits. I myself prefer using external chargers for two reasons:

1 - I don't like to think of having a Spice connected to the AC mains supply for that long;
2 - I take the recomended 10% charging current as the one to be used, and the charging Spice circuit is design to something closed to 50mAh (if I am wrong, guys, plase place the correct figures...), that is 1/3 the recomended for a 1500mAh. Would that be a good choice?

Yeap, I know, this way I'd be openning the battery compartment too often as well, and that's the main reason I choose using rechargeables with current capacity that's closer to the originals and, by doing so, I use them (the two HP38C) as I'd use with the original battery pack, no worries about excessive time plugged in the AC mains.

Wow! Too much words... It's been some time I don't write that much in here. And as this computer has no spell checker, there's a lot of typos, for sure...

Best regards, Paul.

Luiz (Brazil)


1.5V "AA" non-rechargable cells will apparently not damage the internal circuitry of Spices, even though they are designed to run on rechargable cells rated at 1.2V.

However, the full-length cells with protruding positive terminals (rechargable or not) are a bit too long. Even bridged by a thin sheet of aluminum foil, these replacements will put stress on the fragile battery terminals, fracturing them at their crease.

This kind of damage is common, as people didn't want to pay $12 in 1980's money to replace the HP battery packs.

-- KS

Edited: 13 May 2005, 3:52 a.m.


...and when you do break those terminals, or corroded ones up and fall off, I've had great success with Katie Wasserman's fix:


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