What is the best way to charge and use bad lead acid batteries so that they are useful for something as long as possible?
Lots of us have old batteries that are no longer good enough for our primary chair, but might serve ok for a backup chair, pathway lighting, emergency backup power, hoist batteries, 2nd vehicle battery, water pump, whatever. The use case boils down to discharge duration @ current draw.
They may be gel, AGM, SLA (maintenance free), even flooded vented batteries requiring added water. Battery type and original nominal capacity (Ah).
They might have died from deep discharge, overcharge, frequent short cycles, long time between charges unused, overheat, freeze. Cause of death.
There are a few different reasons batteries go bad, shorted cells, sulphated cells, low electrolyte. Condition of death.
Assuming we have a good hobby charger and can customize a profile for a particular battery, what are some best practices for extending the useful life of "bad" batteries?
For example, if we suspect a battery has one or more shorted cells because it's voltage is down an exact multiple of single cell voltage, can we set our hobby charger to lead profile of fewer cells to power lower voltage devices.
Desulphating charge profile. Is it complete BS, or are there specific combination of conditions where it sometimes helps? Conditions where it never helps?
If a battery is already sulphated, is it better to push a lot of amps into it fast, or trickle charge for a long time? What kind of load can draw the most energy from a sulphated battery? Low discharge current over a long time? Or high discharge over a short time?
Is there anything we can learn about a bad battery by comparing its original nominal Ah to its present Ah measured by a hobby charger?
Do specific causes of battery death lead to specific conditions of death?