Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Thanked 31 Times in 31 Posts
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I don't have a trickle charger, I use a 80w panel and a 3 stage regulator specifically for that panel in everyday usage.
I have a 3 battery house bank and 1 starter charged by that, all AGM's, all the same battery (Spiral Blue tops). I set my monitor in the winter to 99% of total capacity (meaning it THINKS that is full) and my batteries just stay there. No chance of over charge that way.
Temperature and battery type matter, if you have any reasonable expectation of your batteries freezing, you are better off taking them home and putting a regular 110v charger on them monthly for a couple of hours.
Wet cell batteries can, IIRC can degrade / discharge far faster than AGM's, and my AGM's are rated at 2% per month. You need to dig into the spec's of your batteries, figure the unloaded discharge rate, add in the expected bilge pump drain, other current drain's (co2 detector whatever) etc - and then get a trickle charger capable of overcoming all of that - and never trust a solar panel's maker of giving your the real average output of his panel - go with 80% because of dust, dirt, leaves, shade etc.
If you are just doing a starter battery, just take it home and trickle it off a 110v charger every couple of weeks, it'll be cheaper.