oh the irony....i have a load of spare 12v lead acids left from my ebike....which im using in what ive come up with instead of the initial idea.
tbh Pb batteries last quite a while if you make sure they dont go dry or over sulphate.....i always find it weird that batteries used to be a maintainable automotive item but now they're suddenly disposable
add proper distilled water when dry and use a good desulfating charger/device every now n then and they should be fine.
ive half given up on the battery grid tie inverter.....its non nessesative to my current setup/arrangement after actually increasing my power usage via profitable bitcoin mining.
using some junk i had about ive done something similar.
ive invested in extra smaller panels (6x20w flexibles) and cheapy boost converter (mpt7210a) its charges a 24v (2x12v 22ah) battery bank using one of those lead acid balancers. this battery bank powers a 1000w computer uninteruptable power supply/inverter.. on a full charge itll run an (all in one) pc i have for over 4 hours.,probably longer but i havnt left it on.
im still testing at the moment but its has the scope to last even longer when i add a the extra batteries.
so far its been £30 for the mpt boost charger, £14 for the lead balancer, £40 for the pc UPS off a mate, and 120 quid for the panels. the batteries were mostly from a charity shop from years ago but i think it worked out at like £20 for 8 of them. so £224 so far.
at 15p a kwh cost.....it would need to run 1493kw through it to break even.... thats 1kw for 62days worth of hours at the inverters maximum output.
honestly for the power output/input it kinda doesn't seem worth it. The current ROI seems more like 3-5 years....but i suppose i have nearly all the building blocks i need to progress. i can always change/add more panels, batteries....or even get a grid tie inverter in the future.