Here's a tip on lawn mower battery maintenance that will save you from buying a lot of them. Don't let them run down by setting around! For $15 or $20 you can buy a good quality "trickle charger" at Walmart or wherever. The point, however, is that "trickle charge" means nothing. It is the fact that, correctly designed, these devices will float the battery charge at exactly 13.7 volts, no more, no less. This is a critical design element of any lead-acid battery. Floated like this, they will last for years and always maintain full charge. Stay tuned.