8x 18650 batteries 2600 mAh and a DIY powerbank case from Aliexpress(3$) is all you need.(but you can use others batteries,important is: not depassing the limit of internal circuit).
Complete charge need 30 hours(in my project) but is possible to add many circuit of charge on external case
like this https://www.amazon.fr/gp/product/B078R5HBMV/ref=o... and not depassing 1A charge for every battery(8 ampères max on charge for save batteries integrity).
And many many energy for all outdoor moments.....
Thank you to watch.