Been caught out twice this winter when my main Victron MultiPlus setup threw a wobbly and I had nothing sensible to fall back on — proper embarrassing when you're supposedly "off-grid ready."
Currently eyeing up a beefy Fogstar Drift 12V 100Ah as a standalone emergency bank, just sitting there on a trickle charge doing nothing until needed. Reckon that plus a cheap 300W inverter would cover the basics (lighting, phone charging, small pump) without bankrupting me.
The bit I can't work out: do you keep your backup completely isolated from the main system, or loosely coupled so it tops up passively from the solar? Feels like every way I wire it introduces some new failure point, which rather defeats the purpose.
Anyone actually tested theirs under proper stress conditions rather than just assuming it'll work when the main bank dies?