How long is it driven when it is driven? Starting the engine ang pinakamalakas maka-drain ng baterya. Kung short trips ka pa lagi, hindi na narerecover yung nawalang charge from starting up the car. So you end up with a battery that is always partially charged. Pag partially charged ang battery, nagkakaroon ng crystallization sa charging plates. In other words, nagde-degrade. Pag hindi na maayos ang plates, hindi na magho-hold ng charge ang baterya mo.
Covered garage ba? Kung mainit dahil parating bilad sa araw, may negative effect din sa battery.