Sometimes we do things just for “the love of the game” and learn something along the way but I couldn’t help scratching my head the entire time while reading this
> I have a power inverter, meaning I can use appliances with normal/household plugs, but the inverter wastes some power in the conversion process, stepping up from 12V to 220V. To then plug in a power brick, which will again throw away some power in converting 220V back down to whatever voltage a device uses, means double wastage, and a mess of plugs and wires.
Is this... a joke? How much freaking amps are you pulling? Average Canadian electricity consumption is 1270 watts. 1270 / 12 = 100+ Amps for one hour.
I'm guessing this is more of a third world situation and that electricity usage is much lower, but still...I fail to see how you would get to a setup like this. If you're fully off-grid then your generator or solar system could give you much higher voltage. If not, how are you charging the battery bank?
EDIT: From your CV, you are from the UK. I'm very confused.