Just in case you’re wondering what a Battery Tender looks like. The original Battery Tender is a little expensive, but can be left hooked up to the battery for the entire time. I use mine about once a month on one of my older cars to keep the battery topped off. Check out the original Battery Tender or Battery Tender Jr. here.
You could also purchase a less expensive trickle charger. In my opinion, the Battery Tender is worth the extra cost. It’s still cheaper than a new battery.
Ed B.