Just wondering when this is required? When your batteries rest at a low voltage or?

Ideally you would make it a part of routine maintenance.

Depends on what type of battery, generally if its AGM and you notice it resting under 12.7v i would put it on an intelligent auto matic regulated for AGM charger as it will more fully charge your battery than your alt will or can. You want to push back against sulfation as much as you can and a more complete charge = less loss/potential loss to sulfation. For a wet flooded cell (normal battery) if it were down to 12.5ish I would use the same type of charger on it as it is safer and charges more fully and requires less guess work. If you find yourself having to do this often I would check your wiring and alternator/regulator.

Edited October 8, 201014 yr by audiolife