Lead batteries can be rejuvenated, with a device mostly called "A pulser/desulfator/refresher" Short story: I had a completely dead 12V car battery. It was at 0V and would not accept a charge at all. Connected it to a bench power supply and slowly cranked the voltage up until it charged with a couple mA @ 30V. Slowly it accepted more amps so I constantly dialed the voltage down until it was charging at 14volts. Then hooked up the desulfator and left it for couple of weeks. Every other day checked voltage and hooked it up to a charger for couple hours. After that it was perfectly able to start my car(oldtimer) again.
This kind of work requires a supply of power though, which is something of a catch 22 if the battery you are rejuvenating is your power source.
That said, this thread has descended from a comment about apocalyptic scenario planning and this general principle of maintaining batteries makes sense. Learning how to build and repair lead acid batteries doesn't seem to be beyond the realms of possibility.
I believe desulfating is based on trickle charging, so doing it via just solar might work. And if we're talking apocalypse, it'd be good to have a secondary source of power like something that can run off of organic material such as wood gas.
The desulfator i speak about is powered by the 12V battery itself. It's a small box with just get hooked up to positive and negative. Technology differs but basically it charges a capacitor and produces very short high voltage charging pulses that break the formed sulfur crystals.
Yes, this will deplete the battery if it's not charged otherwise.
