Originally Posted by Ken Maltby
Hmm... I'll have to see if I can rig a ground for the adapter's USB connection at pin 4.
(If there is not one there already.)
You wouldn't want to have the unregulated output of the solar panel go directly to
the power pins of the Libre's USB port. The power regulation of the charging circuits
are likely limited. Having a properly sized solar panel go directly to a battery is less of
an issue. Having even a number of small panels go to an adapter, designed to regulate
the power from the much greater amp capacity of an automotive electrical system, is
a simple and inexpensive measure to insure compatible power for your device.
The input to a USB port is certainly expected to be regulated and should not exceed 5.1 Volts, nominally 5.0 V.