What is Battery Deficit Cycling?

When Batteries Cannot Be Fully Charged Being Discharged Again i.e. Renewable Energy Applications

Information from RollsBattery

A batteries long life is dependent on the correct charging regime.
To fully charge a lead acid battery, more ampere hours must be returned to it than have been drawn from it. This is not always possible in Renewable Energy applications as systems may rely solely on the Sun and Wind without backup power (generator/charger). In these instances the battery may not receive a full charge before it is discharged again. If this deficit is not corrected the battery will eventually sulphate and its capacity will deteriorate. To lessen these symptoms it is essential the battery is returned to a fully charged state at least once a month. The battery’s state of charge (SOC) can be checked using a combination of its voltage and specific gravity.
If the batteries do not respond to normal charging, a course of equalization* will be required. This is in essence controlled overcharging in order to return the acid back into the electrolyte. Given that the acid is more dense than the water, no noticeable increase in the specific gravity will be noted until the gassing voltage has been reached (2.4VPC) and the two start to diffuse.