Battery Tender works great.

I have been using the Schumacher INC-406A (4) bank charger for a while and it has never failed me. It can charge lead-acid and AGM batteries. What I like about it is it puts a battery through multiple stages (desulfation, charging, maintain). The unit is all metal and can be mounted to a wall. I purchased the extension leads which gives me about 25 feet of range per lead. It does take 8 to 24 hours to charge a 12V - 1000 CA battery and there is some fan noise when the unit is in desulfation/charge mode (maintain mode is silent). Best charger I have used and I have used a lot of them!

Here is the amazon link:
https://www.amazon.com/Schumacher-IN.../dp/B00396JEP4