42 AH refers to the amp-hour (Ah) capacity of the battery. Amp-hour capacity indicates the amount of current that the battery can continuously supply for a specified period of time. In simple terms, it the energy stored in the battery. In this case, 42Ah means that the battery can continuously supply 42 amps of current for one hour or a smaller constant amperage for a correspondingly longer period before being discharged
Maintenance-free refers to a type of battery that does not require periodic maintenance such as the addition of water to the battery . Maintenance-free batteries commonly use Valve regulated lead -acid (VRLA) technology where internal gas recombination occurs , eliminating the need to add water to the the cells
