Just been to a caravan centre were they had a solar panel for motor homes+caravans 65 squid or bigger one 145 squid ,thought it may be of interest to you fellow wfpolers diy whose using battery boost packs,charge up as your working.
IT SAYS:THEY DONT NEED SUNLIGHT TO WORK,
IF you lose time cus of lack of power[go home early] you may get enough power to see you through the day+ it will save electricity at home when you have to recharge.