Charging Lead-Acid Batts with Very Small Charger

[Maine Sail]

You can always take your good batteries off-line and insert an inexpensive buffer battery such as a low price auto or lawn and garden battery. So long as the charger can support the loads, and keep the small battery charged, you'll be ok. If something hiccups you're only out a few dollars for the cheap battery.

A customer of mine does this with a U1 lawn & garden battery. I think it cost him all of $23.00 at Wal*Mart. He works on his boat quite a bit in the winter, and had previously ruined a 1.6K bank of AGM's by leaving it unattended and charging and power was interrupted....