HP-33E batteries


I have an HP-33E that is missing the battery pack. What can I replace it with and is there something that bridges the two batteries on the side opposite the contacts?




You can use two AA rechargable batteries (or even alcaline). Of course you have to bridge the oposite contacts (3V aprox. are needed). Take care with the polarity. The (-) is the contact closest to the keyboard side. You can get more detailed information about batteries and chargers in the main page.



Minus (-) is closest to the top edge of the calculator.


Sorry for the wrong information. David is right. Minus (-) is closest to the top edge of the calculator.

I have repaired four spices. I use the metalic structure of the original battery pack. Then I place two new rechargable batteries. I can charge them externally (with an standar charger) or even inside the calculator with the original charger.

I all of them the plastic connector was corroded and I had to replace it with wires. I had also to rebuilt the contacts (the most difficult thig is opening the calculator)





Describing the battery polarity this way is worrisome:

"Take care with the polarity. The (-) is the contact closest to the keyboard side."

Due to the various angles & things, it seems somewhat vague.

I would suggest:

"The + contact is the contact closest to the central part of the calculator".

ALSO, about bridging the AA batteries at the far end ?
I have been really wanting some .003" thickness nickel foil for that purpose. It would be nicely corrosion resistant, and very thin.

Not having my first choice, I have been using a piece of "solder wick". It's the very finely braided, flattish copper mesh material. You can use many different things so long as they are THIN.

I have used aluminum foil, BUT, it tends to start shredding apart and leaving little pieces around.


Which is to hardwire a AAA battery holder to the circuit board. Then, you can use alkalines, Ni-MH rechargables, Ni-Cad rechargables, etc. and you don't even need to have the HP charger or equivalent. It seems to me that the risk of blowing up the calculator because of a simple mistake of plugging the charger in w/o a good battery pack in place is an accident waiting to happen. Going from AA to AAA you do lose some battery life, but you never have to jerk around with the charger again unless you want to...

Do you have the charger? If I had the charger, I would:

1. Buy a battery pack for a cordless phone that is made of 2 AA Ni-MH cells. (again, at Radio Shack or equivalent)

2. Cut the wires of this battery pack right next to the connector and throw that connector out.

3. Neatly solder a 9V battery connector to the leads you just exposed. (you guessed it, the 9V connectors are available at Radio Shack for < $2 for a pack)

4. Hardwire another 9V battery connector to the points on the HP circuitboard where the battery terminals are wired to. (Make sure you attach it with the polarity reversed. Since you're hooking two of them together, it will switch to polarity when you plug them together)

5. Run that connector into the battery compartment.

Now, when you want to replace the battery pack again, (10 years from now?) all you have to do is buy a cordless phone battery pack, and replace its connector with a 9V connector and you're ready to rock. Of course, that ruins the originality of the calculator, but it is more practical and lets you get 50% more life out of each battery charge, since they didn't have Ni-MH batteries in the 70s.

If you ever want to sell the calculator on eBay, you won't get a collector's sum for it, but you might get more bidders, since they won't have to also look for the !@#$ HP battery pack.



With using a standard 9 V connector for a 3 V connection down the road when someone replaces the batteries. Granted, the person who makes the modificaion is not likely to accidently attach a 9 V battery, but if the calculator is sold or being used by someone else, who knows.

Just a thought...



when you sell it, you include directions and a good battery pack, you've done all you can do.

If I were to sell such a modified machine, I would detail exactly what I did, and the buyer would be made aware of it from the getgo. If he/she is not smart enough to heed my warnings, then he deserves to hear his newly purchased calculator go BZZZT! (with the whisp of smoke soon following)

Still, maybe it would be a good idea to put a label inside the battery compartment giving a warning not to attach a 9V battery... I'll think about it more if I ever decide to sell an HP, hehehe.



The easiest thing to do is go down to your local Batteries Plus or Batteries Etc and get them to spot weld two AA batteries together. I like to use 1800 maH NiMH cells. They will give you a 15+ hour run time on a full charge.

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