Quote:
Originally Posted by JSWolf
It's not that it's out of spec. The problem could be too low power and that could cause a problem.
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Low voltage is almost never a problem with a modern device. Lithium batteries are usually 3.7V, and any modern design has a diode and a fuse in series with the charging circuit. If you apply a low voltage, or even short that port (i.e. 0V), it simply does not do anything as the diode does not turn on. In other words, you cannot discharge the battery externally.
If you apply a high voltage, several things can happen:
1) If the charging system has a regulator between the battery and the port, it charges ok.
2) If there is sufficient series resistance, the battery will charge fast. Note that this will wear out the battery faster.
3) If the series resistance is low, but there is still a fuse, you'll burn the fuse. A simple fuse exchange can fix this though albeit with some soldering.
4) If none of the above apply, most probably you will damage some IC and/or battery. However, I have not seen any device which does apply to this category in the last 5 years.