This refers to the battery size that will best fit the physical dimensions, terminal. Group size is typically based on your vehicle's make, model and engine type.
A guide to understanding various types of batteries & identifying your best fit: SLIs
In general, these more-common battery group sizes are 24, 24F, 25, 34, 35, 51, 51R, 52, 58, 58R, 59, and 65.
Car Battery Specification charts showing Dimensions, Sizes, Cranking Amps, Voltages, Terminal, Weights and Ampere hours.
Today it's standard to recreational vehicle batteries powering inverters up to 4000 watts.. Safety; Battery types, Deep Cycle and Starting; Wet Cell, Gel-Cell and. . Of course the physical size, cable hook up and terminal type must be a .