Could someone explain to me the relationship between a solar panel's rated watts and its ability to charge 4xAA Eneloops?
I have 2 portable solar battery chargers - the Powerfilm 6 panel, 4xAA, 2.2 watt, 3.6V, (assume that's 600 mah); and the Goal Zero Guide 10 Plus Adventure Kit, which has the Nomad 7 panels which the specs say put out 6 watt, 6V, 1.0A to the 4xAA Guide 10 Plus charger.
Now I've been testing both units side-by-side charging 4 Eneloops. The Eneloops have been discharged in a Maha C9000 prior to the solar charge, and then again after the solar charge to measure the charge capacity. After several attempts in admittedly less than perfect condtions (Dec/Jan, double pane windows, tree branches, etc.) it surprises me that the 6 watt Goal Zero can only muster around 60-80% of the charge that 2.2 watt Powerfilm can for any given length of time. FWIW, the solar collecting surface area between both units appears to be about the same.
Shouldn't the GZ be at least as efficient as the PF in any given light situation? Do you think the GZ would pull away and leave the PF in the dust in perfect sunlight conditions? Is there something wrong with the GZ (I'm thinking about returning it)?