When it is fully charged (after each use).
A high enough voltage with a long enough charging period.
If the battery is not charged the sulfate becomes hardened and may be extremely difficult to remove--it might take an extremely high voltage to do so--perhaps even as high as 17 volts.
This all refers to the negative plates. The positive plates do erode (slightly) with each and every cycle.
red31 wrote:
When is a battery not sulfated?
What does it take to get all the sulfate back to it prior states?
When does it become irreversible?
