I have an HP25 calculator that is in excellent working order. I have misplaced the charger. I need to be able to charge the batteries and I am wondering if I can use a charger for cell phones. I have determined the polarity of the charger connections and have used pieces of bent stainless steel wire inserted into the leads to serve as connection points for clip on leads. What I don't know is what voltage to look for in a cell phone charger? I can easily determine the polarity of the charger and solder on spring loaded clips to the leads of the cell phone charger to attach to the stainless wire clips I have rig up. Does anyone know what voltage I should be looking for in the discarded cell phone chargers that would work. I don't want to arbitrarily use any charger for fear of damaging the calculator. The two rechargeable batteries only need 2.5 to 3.0 volts but the calculator needs more to operate. I have determined this by using an adjustable DC power supply. I understand that the original chargers were unregulated and I am not sure if the cell phone chargers will work. Does anyone have any info that would help me out??
Edited: 4 Jan 2006, 5:37 p.m.