A hobby of mine is to find discarded 12 volt car batteries and rejuvenate them. I don’t do anything clever: if they show 12v then I shake them to move the acid around and then charge. I have an intelligent charger which tests the battery and goes through a vibration cycle to shake sulphation off the plates.
Why bother? In our household we have 5 cars, one tractor, two motorcycles, and two ride-on lawnmowers. The (heavy duty) batteries for my SUV and the tractor cost $300 each. It all adds up very quickly. Plus I like recycling.
Calcium batteries require a higher and longer charging rate than lead-acid. However if I mistakenly charge lead-acid at the calcium rate, that boils the battery and it dies. Regrettably a beautiful truck battery sits at the moment in my garage having been erroneously cooked.
Not many calcium batteries say “calcium” on the label. How can I check?
No-maintenance batteries with sealed tops are usually calcium batteries. However I have two with flush removable plugs which nevertheless claim to be a calcium.