The awful truth about what summer does to your batteries
Battery sulfation begins as soon as a lead-acid battery discharges. This occurs as soon as the battery is no longer being charged whether or not the battery is being used:
Self Discharge is Accelerated by Temperature
For batteries that are over 25°C (77°F), the self-discharge rate doubles with every 10°C (18°F) rise in temperature.
Thus, sulfation can be a huge problem for lead-acid batteries which are:
What is Sulfation?
Sulfation is the formation of spongy lead sulfate within batteries during discharge which are converted back to lead and active material in the regular charge cycle.
How is that a problem?
As most batteries are charged only a fraction of the time than it is discharged, the formation of spongy lead sulfate accumulate more than it has a change to be converted back into usable lead.
Over time, the spongy lead sulfate harden, forming crystals and can no longer be converted back to lead even with constant charging.
What is the solution?
Using desulfators will shatter the hardened lead sulfate crystals and dissolve the active material back into the battery electrolyte (the liquid solution in the battery).