These initials stand for starting, lighting and ignition, which are the three basic functions which a battery has to perform on all normal vehicles.
RANGER Dry-Charge Battery
Ranger Batteries have been specifically designed for service on European trucks within a voltage controlled electrical system. Those SLI batteries which are intended for heavy haulage vehicles fitted with large diesel motors may often be called COMMERCIAL batteries. They have to be much more powerful and more robust than batteries intended for cars.
RANGER Maintenance Free
Valve regulated lead acid battery, these type of battery is sealed, Maintenance Free with a hole Valves in the top of them that opens when a preset pressure is realized inside the battery and lets the excess gas pressure out, then the valve resets itself.