As long as there is still active material in the battery and the plates aren't shorted, any battery that fails due to lead sulfate crystallization has a chance of being revived and reused. This is not only limited to car batteries, but to ALL lead acid batteries! There are already battery clinics in New Zealand now that revive and recondition batteries, which are later sold back to customers at about 1/3 the retail value of a new battery. These batteries are given 6 month replacement warranties!

The graph below shows a typical revival process of a 45 Ah Ca-Ca battery that had failed 2 years ago due to shelf sulfation. Note how the impedance and CCA (Cold Cranking Amperes) are inversely related. The CCA of the battery, initially at 112 increased gradually up to 321. The battery was originally rated at 360 CCA, and it takes about 180 CCA to crank a car.

In this particular example, the battery was revived in approximately 6 hours or so. Do note that not all batteries can be revived in such short periods of time. The speed of revival depends on the degree of sulfation the battery suffers from. Revival can take up to weeks if a battery is badly sulfated as more time is needed to break the lead sulfate crystals.

As Good As Almost New
With diagnostics tools you will know how well a reconditioned or revived battery works. Measurements such as cold cranking amps and internal impedance can be taken to diagnose the battery's health.

Reviving Maintenance-Free Calcium Batteries
Over the years, calcium has been added to lead plates to improve grid strength and conductivity, and reduce gassing and its self-discharge rate. With this, the low-maintenance or maintenance-free battery was introduced. However, the alloy plate is still consists of more than 99% lead. Whether the battery is calcium-calcium, calcium-silver, lead-calcium, or lead-antimony, it is still essentially a lead acid battery.