Battery charger question


Looking at the bottom of my HP-65 battery charger, it lists the input voltage ranges as being 86 - 127 volts and 48 - 66 hertz.

Would it damage either this charger or the calculator to plug it into the A/C socket on an airliner where the voltage is 115 volts and the frequency is 400 hertz? I've seen people do it with cell phones and computers, but would hate to damage my older equipment.

Matt Riehl


The charger is probably just a simple transformer, possibly rectified (I'm not sure about this model).

The change in frequency will not damage the transformer (it will probably make it more efficient though).

My recomendation is to get a resistor of appropriate resistance to simulate the load the calculator will place on it. Measure the voltage across the resistor (if it's simple rectified AC, then a capacitor in parellel may be a good idea). Then do the same thing for the 400Hz aircraft supply. A difference of more than (say) +20% would worry me.

Are you air-crew? if not, they might not like you pulling out a multimeter etc... :-) If you are, then I'm sure you could ask engineering staff the same question. In fact you could probably ask them anyway. If you can find an older engineer that had (has!) an old HP calculator you may have found someone who would care enough to answer.

The other (and maybe better) alternative is to go to (Professional Pilot's RUmor NEtwork), register yourself, and ask the same question in the technical forum. (While you're at it, maybe you could say where you came from and we might find some more HP calculator users :-)


Classic chargers are most certainly _not_ simple transformers. They contain electronic circuitry to provide both regulated voltage that is used to operate the calculator, and regulated current for charging the batteries.

Personally, I don't see why the charger wouldn't run off 400Hz. The only problem I can think of is that its transformer will run more efficiently, yielding excessive voltage. However, I don't think that the difference will be such that it would damage the calculator.


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