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HP 67 battery charger - Printable Version

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HP 67 battery charger - Paul Davis - 04-18-1999

Can anyone provide a specification or circuit diagram for building a battery charger for the HP67?

Many thanks,


Re: HP 67 battery charger - DaveC - 04-18-1999

I'd actually buy an existing stabalised supplyand change that. The only additional component you need is a current limit resistor and a power diode. The important operating voltage is that that runs the calculator which needs to be set accurately at 3.75 to 4 volts. The additional diode and resistor can be used to form a charging circuit direct from the secondary of the transformer. I'd choose the resistor to pass C/10 to C/15. (C=Capacity of cell).

Re: HP 67 battery charger - DaveC - 04-18-1999

Also see http://www.hpmuseum.org/batts/battery.htm