Need batteries for HP-31E

[Danby74]

my HP-31E has the metal battery clip. i understand i need flat-top batteries.
i've heard people say they use regular aa eneloop batteries.
i've heard people say they use flat top nimh batteries.
i've heard people say they use flat top nicad batteries.

can someone recommend an actual battery listing on amazon or ebay?
i want to recharge them myself.

[John Garza (3665)]

Battery

[Danby74]

thanks!!

[isanchez]

may I recommend you this AAA battery holder...it is amazing! and you will be able to use any AAA type (disposable or rechargeable) and the calculator does not suffer the press of "big" modern AA batteries...for me it is a "must have" to enjoy HP spice series again.

https://www.thecalculatorstore.com/epage...ts/Spice3D

regards

Ignacio

[vaklaff]

+1 to Ignacio

In spite having a rebuilt NiCD pack I prefer using that holder (with disposable AAAs). More convenient and I believe safer too.

[John Garza (3665)]

A good point to bring up here is corrosive gasses emitted by NiCds.

Alkalines last much longer before they emit, whereas NiCd will emit even before they are dead.

SO... if you plan use use your Spice as a 'daily driver' - meaning that you keep batteries installed in the machine even when it's not in use, then the triple A alkaline batt pack is ideal.

I NEVER keep NiCd batteries installed in my calcs when not in use. I have a separate sealed battery box with the various packs charged and ready to install when needed.

Luckily though, the Classics and Woodstocks have plenty of room to install Double A Alkaline battery packs. The Spice has a smaller battery well that won't accept Alkaline Double A's without mods (or cracking the case!)

-J

[ctrclckws]

Never had any of these devices. My HP journey started with the Voyager series

But, seeing all of these battery cautions reminds me of why I am leery of buying an electric car.

Amazing that the HP devices continue to work 40 plus years after they were designed and built, as long as people respect the safety concerns.

[Maximilian Hohmann]

Hello!

(10-30-2023 04:12 PM)ctrclckws Wrote:  But, seeing all of these battery cautions reminds me of why I am leery of buying an electric car.

Electric cars use a completely different kind of batteries than those 40+ year old calculators! Most importantly, the batteries have integrated battery management systems (https://en.wikipedia.org/wiki/Battery_management_system) which protect the battery cells against overcharging, overvoltage, overcurrent and deep discharging. The cells are balanced, i.e. regulated individually to the same voltage, so that stronger cells can not reverse charge weaker ones (which is one of the main chauses of battery failure in calculator battery packs).
Thereby all the factors that cause the batteries inside calculators to eventually leak are eliminated. Additionally, the battery housings in cars are made from plastic which can not be corroded through by the electrolyte like the thin sheet metal housings of our calculator batteries. And, contrary to some common belief and urban legends, the battery type used by most car manufacures is Lithium-Iron-Phosphate (LiFePO4) which, other than the Lithium-Polymer ("LiPo") batteries used in small devices like smartphones, does not suffer from the "thermal runaway" phenomenon which can cause battery fires and explosions.

The short version of my long offtopic blabla: Our electric car is one of the three best things I ever bought. I will never return to petrol driven cars. Statistically, only 5 percent of car fires occur with electric vehicles - a figure already corrected for their smaller number. Maybe one of the reasons that the insurance for our electric car costs less than for the previous petrol one. And for peace of mind, the manufacturer gives 8 years warranty for the battery. By the way: the same type of battery is used for power storage in photovoltaic home electricity generation. The manufacturers - at least here in Germany - give 20 years warranty for the batteries. One wishes that HP had done the same with their calculators ;-)

Regards
Max

[ctrclckws]

Thank you, Max, for your comments on the battery types and your experience with them in cars.
It will still take some time before I will be ready to make such a switch. I do hope my current old school manual shift car lasts until I see many more reports like yours.

Perhaps I am still hoping for Robert Heinlein's 95% efficient solar screens and this shipstone storage technology to come to pass.

Dreaming, I know.