Any boat that is moored where there is shore power available will benefit by having a battery charger that converts AC power to DC power which can be stored in the batteries. Battery chargers are one of the most common devices installed as part of the DC electrical system and are used to maintain and replenish the batteries. Battery chargers are often installed as stock equipment by most major boat manufacturers.
Battery chargers have evolved from ferro-resonant style transformers that charged at a set output, and were only regulated by the resistance of the battery bank they were charging, to modern day switch-mode electronic chargers that charge in modern three stage charging protocol. Many boat owners have taken advantage of the changes in charging technology and have upgraded their battery charger or installed a battery charger as additional equipment. There are some installation criteria that are common amongst all battery charger installations, and some of the detailed points are sometimes missed.
The most common installation criteria missed is the addition of a chassis ground. All power generating devices, including transformers, converters and inverters, should have a ground cable that is the same size or no more than one gauge smaller than the largest cable used for power cables.
Battery chargers should be directly cabled to the battery bank so they can charge even when the battery disconnect switch is in the off position. As such, they require over-current as stipulated in the installation instructions from the manufacturer, and as recommended by electrical standards and good installation practices.
It is also important to maintain good sized DC cabling to minimize voltage drop on the line, and AC wiring should be adequate to support full load, with a dedicated AC GFI circuit and breaker to power the device.