> Solar panels and batteries are both DC so you don’t need an inverter, the charge discharge efficiency of lithium ion can be over 90%. You'll still need a DC-

> Solar panels and batteries are both DC so you don’t need an inverter, the charge discharge efficiency of lithium ion can be over 90%. You'll still need a DC-DC converter, which is just an inverter with a rectification step. The 81% number is low, but there is a loss here.