HP 29c power requirements


does anyone have power requirement stats for a 29C?? specifically, can it be powered by AA or AAA batteries or is the rechargeable pack required. and if so, what are the specs of that pack??? i sold one on ebay that was in questionable condition (stated so in the ad) and now the guy that bought has informed me that it doesn't work. i just wanna make sure that he is using a battery with the correct voltage etc.

thank you for any help you can offer.



Two AA alkalines will power a 29C without issue and is by far the safest way to test and otherwise use it.

*Never* attach the charger of a twenty series unit to the calculator without a known good rechargeable battery in place. A bad battery, bad contact or doing so without a battery in place will destroy the unit.


thanks for your help.
I am certain that the unit has been on AC power with a crappy battery in it, and is probably toasted. is the unit repairable??? i have sold it and did not mean to mislead the buyer. I want to make good on the deal whatever that means, whether that is a repair or refund.

thanks again...


If it has internal damage, and it most likely does, repair isn't practical since the required parts must come from a good 29C.

You'd be ahead of the game by getting it back and giving a refund. Then resell it as a parts machine, not working, as-is, no returns. Somebody will buy it for the battery tray and the keyboard, especially if it is in decent cosmetic condition.


Thanks again Randy,
the thing is in excellent cosmetic condition, the keyboard and display are perfect, and the battery comp is too except for a spec of corrosion on one of the contacts.....do you have any idea what a unit sold for parts is worth??


IMO, I'd say at least $50. Might go for double that, just no way to know. Good photos = better bids.


thanks for the info....
youve been a great help.



The power requirements of all 20 series (Woodstock) calculators are stated on the label on the back of the unit, located between the 2 bottom rubber feet, and are 2.5V, 500 mW. The source of the power does not matter, provided it is applied at the battery terminals inside the calculator, it is DC, and proper polarity is observed (the positive terminal is on the left side of the calculator, same side as OFF/ON switch). As stated by Randy, NEVER operate the calculator with the AC battery charger, unless a good NiCad battery is installed. This also applies to the 30 series (Spice) calculators.

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