Given the saying "The crux of the matter is that silly people are always sure, yet the smart people are so doubtful." (haphazard translation), i would check the product or campaign description on how carefully the wording is crafted to not have a legal problem. If the creator of that project really believes to have reinvented the chemical solution dynamics in galvanic lead acid reactions and tries to sell a product with that claim... i doubt he will be able to write a text that circumvents legal trouble (he dubbed it "self recharging", as in relevant, measureable and usable raise of contained charge).
OTOH any contract based on impossible claims would be contrary to public policy/immoral (therefore imho illegal, based on the legal situation as in germany), and with knowledge of said impossibility it could be seen as an outright fraud.