My battery died back in 2013, so I bought the Ctek charger below. $$$ but it completely recharged the battery and has a winter storage mode for extended storage. The original battery was still going strong when I recently switched to a Braille battery, but I keep it hooked up (under the hood) whenever I don't drive it.
https://www.amazon.com/CTEK-56-353-1...&keywords=ctek