I'm bringing my '18 in for a battery test next week. About 6 months ago it was low, but it charged up and passed the test so it wasn't replaced. Hopefully it'll fail and I'll get a new one.
I got a CTek charger, I'm going to use it once a month in hopes the battery will last longer.
You can test voltage with any multimeter that can test dc voltage. Here's a link to what the voltage means:
https://www.google.com/search?q=car+...algw5asHwsoycM