Re: Can this actually work? Message #2 Posted by Katie Wasserman on 9 Apr 2011, 11:56 p.m., in response to message #1 by Michael de Estrada
This looks like a straight USB cable with no molded-in voltage conversion circuit, however.....
A USB port can supply at least 500ma, so powering the calculator is certainly possible. 5 volts is also fine, I power all my classic calculators from 3 x AAA Energizer lithium cells which works out to be 5.1 volts when they are new.
Charging the 3 nicad cells in a classic from a 5V DC source will work fine as well. Nicads are fully charged at 1.45 volts per cell, so 5 volts will do it.
The high voltage that you measure from the standard HP chargers/adapter is an open circuit voltage, it drops considerably when loaded. Also as long as the voltage across the nicads cells being charged is greater than 1.45 per cell they will fully charge. The current flowing determines how fast they charge.
-Katie
|