I got a really good battery charger/maintainer that would run on a programmed setting, and would once in a while actually overcharge the battery bank to keep it in good shape. I had a Heart Interface Inverter/Charger set up too, and that worked well, except the batteries didn't seem to like it very much.
I now have a good 3-bank charging system From Xantrex Truecharge 40 and it's worked beautifully. The payback of getting a good system, is the fact that the batteries will last a lot longer.
This is what I'm running now and I really like the brand, and would recommend it to anyone (sold at West Marine, and other outlets).
Here's the scoop:
For boats with large battery banks, the Truecharge 20 and 40 pack more features than any other comparable chargers and supports multiple battery types. The TC-20 is intended for boats with up to two 4D or 8D batteries, while the TC-40 will work well on boats with 4 or 8D batteries or multiples in parallel. Both are bulkhead-mount and intended for permanent installations with hard-wired connections. In addition to the basic Truecharge features, these more powerful chargers include: Three position selector switch for AGM, gel or flooded batteries. Three position temp switch (Hot/Warm/Cold), Optional external temperature/voltage sensor for precise voltage control. LED bar graph shows current output plus "Fully Charged" LED. Automatic 21-day refresh timer runs the batteries though all 3 stages for peak state of charge. Equalization stage allows you to reduce sulfating of battery plates, equalize specific gravity between cells & charge battery to highest capacity. Ignition Protection (Meets FCC Class A & UL standards 1236M, 458, 1564).
Number of Outputs: 3
Automatic Functions: 21-Day refresh timer
User Selectable Functions: Temp. compensation, battery type, equalization
Status Indicators: LED
Temp Compensation: Manual or Automatic
Input Wiring: AC Hardwire
Output Wiring: 3 output terminals
Safety Features: Including reverse polarity protection, AC circuit fuses, over-temperature shutdown, short-circuit protection
Mounting Hardware: Cabling required
Remote Available: Yes (see models 333438 & 333446)
Approvals: FCC, UL
Warranty: One Year
Optional remote panels display charge current, battery voltage to 0.3 volts and charge state on small LED bar graphs
Optional Battery Temperature Sensor (see model 333420)
TC-20 & TC-40 dimensions: 15" x 6" x 2.25"
This is a beautifully functioning piece of equipment, and I have had zero problems with it, and have not changed one battey in what seems like three years. I need to check the fluid level again, but this system will NOT boil out fluid and it does a superb job keeping batteries hot and ready.