I have written but not heard back (maybe because it's the weekend), but I'm running out of time- just bought tickets for Bonnaroo where I"m going with my son (camping out basically) for 4 days starting June 6. I will have a car next to me during the evening so can charge some off the car battery (also have an inverter), but would like to get this right w/ the solar charger before I leave.
I think you're right- charge one battery at a time- wonder if I could do 2 18350's for the VV Woodvil with two of those single bay Xtars? The solar charger we have has 2 USB outs so that's nice, but maybe it can't handle two batteries at once.