I have a 85-640 Napa batter charger. Can I use this charger as a trickle charger to maintain a charge on a standard 12 volt auto battery. I have had to purchase new batteries every year for my lawn mower and am thinking it would be better to purchase a good quality battery (auto) and use jumper cables to start the mower, assuming I can keep the auto battery maintained for several years with a trickle charger.