What actually happened to your car battery to cause you to replace it? Did you do anything to fix it? Did you ever maintain it? Did you replace the fluid? Or did you just drive your car every day and then replaced the battery when the mechanic told you it was broken? It is normally cheaper to replace a standard car battery than attempt to maintain and fix it (100-200$) but in an off-grid situation many thousands of dollars are at stake, which makes maintenance and repair more practical than replacement.
Car batteries these days are sealed, so you don't really have much opportunity to replace their acid. A regularly-driven car isn't deep-cycling its battery, so I'm not sure what else you'd do to maintain it.
You test it regularly and hook it up to a good desulfator/maintainer when needed. A sealed battery might be acceptable for a car, if the owner has the money to replace it regularly, but not in an off-grid/residential situation.
https://www.jdpower.com/cars/shopping-guides/how-to-recondit...
https://www.totalcardiagnostics.com/learn/recondition-car-ba...