Today, quality marine battery chargers use multi-stage charging including the monitoring of the voltage in the batteries. In fact, they may be left on continuously if they are installed correctly.
However, before you start you will need to determine where to locate the marine battery charger which should be as close to the batteries - but not too close.
One common mistake is to locate the battery charger directly above the batteries.
Whilst it's important to keep the DC cables between your boat's battery charger and the batteries short; it's important to realize that batteries give off gasses and promote corrosion during charging. If you place the charger too close to the batteries, it will be exposed to these gasses, thereby shortening the charger's life.
Adequate ventilation is required so that it has breathing room and remains cool. Always mount your marine battery charger in a compartment area that can be properly ventilated during use. Do not mix battery types on-board. All batteries should be of the same age and in good operating condition.
Do not make any electrical connections to your battery charger or batteries until the following steps are completed:
Select a mounting location that allows for free air ventilation with a minimum of 8 inches of clear unobstructed space around and in front of the Marine Battery Charger. Open all battery and engine compartments and ventilate for at least 15 minutes before starting the installation of the marine battery charger. Confirm all battery cables can reach each of the batteries and, do not install charger on carpeted, upholstered, vinyl, or varnished areas. Be sure to place the marine charger in an accessible area where all indicators are viewable. Install the unit on a hard surface.
Mark the position of each mounting hole and insure the mounting screws will not puncture or protrude into a live well, a fuel or oil tank or the bottom of the boat. Then apply a silicon sealer in each of the mounting locations to waterproof the screw holes.
Confirm the surface you will be mounting the charger to is adequate in strength and thickness to hold the marine battery charger in place with the mounting screws you have selected. Maintain an obstruction free area of 8 inches around the Marine Battery Charger.
[The following video outlines how to install a Minn Kota Onboard Marine Battery Charger with two battery banks on a boat. Also, he details how to lengthen the wire leads to each battery to extend the reach of the onboard marine charger. This charger will replenish you deep cycle marine batteries and maintain them with a maintenance cycle.]
If you have a small boat like a sport boat, fishing boat or personal watercraft then it's bound to get wet, so you'll want to purchase a sealed or fully encapsulated marine battery charger which are designed for use in demanding environments.
Boats with gasoline engines must use chargers that are ignition protected and conform to the appropriate UL specifications, which include testing in an explosive environment.
Once the location for the charger has been selected, it may be fastened in place. If the charger weighs more than a few pounds it should probably be through-bolted. If it is of modest weight, and the bulkhead or structure it is to be fastened to is sufficiently thick, then screws may be used. Be sure to use stainless steel fasteners.
Prepare each battery in advance by cleaning each terminal post with a wire brush until a shiny surface can be seen. Run cables free from sharp objects and hold each in place with cable ties. Coil excess cable, do not cut or shorten the length of the cables. We recommend the use of wire ties or cable clamps to provide strain relief for the cables and to reduce the risk of damage to the cables or connections.
Your battery charger will not operate properly if it is not connected properly to each battery. Make sure all connections are correct, tight, and free from corrosion.
Ensure you wire your marine battery charger correctly. Your charger will not operate properly if it is not connected properly to each battery
Before starting up the system, check all connections for tightness. Check the battery voltage for a reference. Select the appropriate charging regime, so it will follow the right charging sequence and use the correct voltages for your flooded, gel, AGM or other compatible battery chemistry, per the manufacturer’s instructions
You should also check to see whether the charger lives up to its rating.