The specific gravity of battery electrolyte changes with temperature. An increase in temperature leads to a decrease in specific gravity and vice versa.
The specific gravity of the electrolyte of a fully charged battery should be between 1.260 and 1.280, at a temperature of 26.7°C.
Specific gravity adjustments should be made by adding 0.04 points for every 5.56°C above 26.7°C or subtracting 0.04 points for every 5.56°C below 26.7°C.
Measure the electrolyte density in each jar. A difference in density of 0.04 or greater between any two banks indicates loss of electrolyte or sulfation of the plates.
If the electrolyte density is lower than required. but the same in all banks, the battery needs to be charged.
If you are using a maintenance-free battery, the condition of the battery can only be checked with a voltmeter. In batteries with a built-in charge level indicator, the battery status is determined by the color of the indicator. The green color of the indicator indicates that the battery is fully charged. The black color of the indicator indicates the need to charge the battery. The blue color of the indicator indicates a low electrolyte level in the battery.