electric battery/lead-acid

About
A lead-acid battery is a type of rechargeable electric battery commonly used in automobiles and marine craft.

Sulfation
Lead-acid batteries are subject to gradual sulfation, which hinders the battery's performance and eventually makes the battery unusable. Sulfation occurs most rapidly when a battery is left in a low-charge condition for extended time. Sulfation appears to be the primary cause of natural mortality in lead-acid batteries.

There is an electrical process which can substantially reverse sulfation, though it is not clear how completely it can do so. It can, nonetheless, restore an otherwise "dead" battery to useful life, and there are both inexpensive commerical devices and publicly-available circuit diagrams for accomplishing this.
 * Desulfator for 12V Car Batteries, in an Altoids Tin: circuit and project plan
 * Schumacher 75/20/10/2 Amp Car Battery Charger: battery charger with desulfation capability