Can't OP using a cheap solar panel ?, I was try to modify Philips lamp that have built-in solar panel and use it for my laptop and its successfully only cost around $100, I forgot its model but its Philips lamp, and its have 24v DC output, so just add simple DC step down will do the job in my case I step it down to 18v DCBoth the generator set and the solar cells array cost quite a bit and take up a lot of space. Swapping charger and computer on one battery have zero additional cost.
like this
https://www.lighting.philips.com/pr...aire-floodlights-solar/LP_CF_BVP085_EU/family
