Restore ni-cd battery pack

How to repair and enhance the Texas Instruments BP-6 battery pack* (see disclaimer below).

Ni-cd battery lose the ability to take charge after 500/1000 charge/discharge cycles, but the battery pack life is usually shorter due to common misuse: total discharge (pack is damaged if not charged for months or years) or overcharging. With the original Texas Instruments BP-6 battery pack dead the calculator became unusable, also when the power adapter is connected. The reason is simple: dead battery short the charger or act as open circuit making the adapter current unstable and potentially dangerous for the electronics. The solutions is simple: you have to rebuild the pack with new ni-cd elements.

Disassemble the pack using small screw and cutter. Remove the old cell and clean the internal circuit. Usually you will find severe corrosion due to battery leckage. You can easily replace the dead cell with new ni-cd cell (use model with terminals for soldering iron). We tested a different 'definitive' solution with replaceable battery. We solded on the printed circuit two metal strip as battery contacts (take the maximum attention of short circuit!) and built a spring back connection. The internal BP space is not enough for standard AA cell, so we used two short 450mA ni-cd cell that's fit wery well. Close the pack using adesive film.

(*) 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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