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recycleseedeez (8622)- Feedback left by buyer.
More than a year ago
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Reviews (1)
Feb 09, 2016
An ingenious solution
0 of 1 found this helpful Let's face it, the HP35, 45, et. al., pocket calculators, revolutionary when first introduced in 1972, have long since outlived their indispensability. Still, those of us who bought one at the time like to get them out every once in a while.
If you're like me, your original battery has leaked and you've lost your plug-in charger. I had a calculator I couldn't use. I found a vendor selling batteries (and bought one), but when the batteries run down, what do I do?
That's when I stumbled on this USB charger assembly. Truly an ingenious and simple solution. Whoever designed it has married a standard USB 1.0 A connector to the special-purpose battery connector for the HPxx calculators. It uses the power connections (and only the power connections; the computer does not recognize the calculator as an attached device) to provide power to the HPxx (and to charge its battery, if you have one).
My only reservation is the voltage. Standard USB power specs center around a nominal 5.0VDC. The calculator is specified at 3.75 volts. I don't know if the calculator can withstand 5.0VDC at all/for an extended period/??? Nor can I find any documentation about supply voltage tolerances for the HP-45. There is no documentation with the cable to indicate what (if any) limitations this places on its use. Since there is no documentation, it also can't be determined if the developer put some sort of dropping resistance in the path to get the target voltage to 3.75. This would be unlikely, as it would not only waste USB power in the form of heat, but it would require knowledge of the specific load of each HP calculator.