HP Forum Archive 01

[ Return to Index | Top of Index ]

HP 67 battery charger Message #1 Posted by Paul Davis on 18 Apr 1999, 9:28 a.m. Can anyone provide a specification or circuit diagram for building a battery charger for the HP67? Many thanks, -Paul

Re: HP 67 battery charger Message #2 Posted by DaveC on 18 Apr 1999, 5:13 p.m., in response to message #1 by Paul Davis 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 Message #3 Posted by DaveC on 18 Apr 1999, 5:14 p.m., in response to message #2 by DaveC Also see http://www.hpmuseum.org/batts/battery.htm

[ Return to Index | Top of Index ]

Go back to the main exhibit hall