If the batteries are not already fully charged, this can be an indication of sulfated batteries which may be causing a higher-than-normal internal resistance. Capacity of the bank will be reduced and can be confirmed by running a load test. An increase in bulk charge voltage and/or absorption time may be necessary to de-sulfate the battery bank. Increase bulk/absorption charge voltage in 0.05 volt per cell increments or increase absorption time in 15 – 30 minute increments as necessary. If the battery bank is heavily sulfated, an equalization may be necessary. Perform an equalization charge if specific gravity readings are <1.250 or vary by more than 0.015 volts between cells. Sulfated batteries may heat up more than usual. Follow the guidelines for controlling maximum charging temperatures.