The 12-volt battery is one of the important and overlooked parts of your vehicle. It not only starts your vehicle but with the help of the alternator charging system keeps your vehicle running. Many off-road and overlanding vehicles use a two-battery system, one for the main and one or auxiliary accessories.If you have the answer to the following question(s) please email them to: info@aftermarketbuildersguide.com – What is the factory battery size?