For the weed trimmer and lawn mower I purchased at U. S. chain Lowes, the magic number of batteries is 3. The mower came with 2, and the trimmer with 1. The cha

For the weed trimmer and lawn mower I purchased at U. S. chain Lowes, the magic number of batteries is 3. The mower came with 2, and the trimmer with 1. The charger can charge a battery almost as fast as the mower can consume them, so the third is needed for a little slack. You could get by with only two if you're content to get a beverage between batteries. Theoretically, anyway; with our tiny yard this is seldom tested. Which why I'm annoyed by neighbors that buy a new gas-powered mower. There is not a yard within at least a 3 mile radius of me that can't be mowed by a modern, lithium-battery push mower.