I installed two of these on the Islander. One per battery. It is a self contained, waterproof, solid state 1.5 amp charger that also has a float mode. It has 6' AC and 6' DC leads so is easy to mount and LED status lights for power and battery status. I have used the same charger in the last 4 boats with great success. The only modification I made was to cut off the 3-prong plug and hard wire them directly to a circuit breaker on the AC panel. You can find a variation of this pretty much anywhere (Sears, Advance Auto, Overtons, Bass Pro, etc), the only difference is that the Attwood has the nice long leads. It happens that I was cruising through a local WalMart and found these up on the wall for less that $30 each. These are NOT suitable for a rapid recharge of a dead battery, but using one per battery has worked very well on all of our boats. They just quietly chug away and the batteries are always fully charged.