Used this with the EXP48 battery on a backcountry canoeing trip. Left the panel open on top of our packs in the canoe, sunny days. Charged the battery from 2 bars to 3 bars all day. Meh...but about what was described. Enough charge provided that I was able to run my cpap for 4 nights vs my test of the battery at home which did not make it through the 3rd night. Son charged his phone camera 30% or so that got it through the trip as well. Seems robust. Lashed it (folded up) on top of one of the dry bags for the portages and it survived.