Restore ni-cd battery pack (2)

How to repair or enhance the HP three cell battery pack* (see disclaimer below).

	Calculators as the HP-35, HP-80, HP-67 (and other) with three ni-cd cell battery pack usually stop working when pack lose the ability to take the charge due to age. The battery act as current stabilizer so is necessary also when the power adapter is connected.
	Our idea is to use the original battery enclosure in order to install any standard AA ni-cd battery or alcaline cell. Start disassembling the pack. Break carefully the plastic; save the metal fingers as long as possible; clean-it very well.
	Restore the battery metal fingers using two side adesive film. Use two copper strip to build a series connection between the battery elements. Use double side adesive to take in place the copper strips.
	Install the battery elements and reassemble the pack using adesive film. Check carefully the polarity (+ should be to the upper right contact see photo; remember: if you made mistake you can easily destroy both your calculator and the battery) insert the battery and test. If you're using ni-cd connect the charger. After few minutes switch-on the calculator and check: if you see unstable blinking display switch-off and check the battery and the battery springs. If ok recharge your battery overnight. The charging time proportionally increase if your battery have more than the 450/500 mA original capacity. Don't use the adapter/charger with non-rechargeable battery: they could leak or explode!

(*) Disclaimer: We offer this repair experience as it is, without any warranty about contents or results (results depends by your personal ability, electronic knowledge and also lucky). Use this information at your risk: we are not responsable for injury or damages eventually caused.

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