The marine battery switch is an excellent addition to any boat, allowing the use of two batteries.
With a battery switch you can alternate between both batteries, or use both at the same time. This
also allows you to charge the batteries independently or both together. You can turn the switch
off to keep the batteries from discharging from accidentally leaving something on when boat is not in use.
The best setup would be to wire the automatic float switch for the bilge pump direct to one of the
batteries, thus allowing to turn the battery switch off when the boat is not in use. If staying overnight
on the boat, this would allow the use of a deep cycle battery for lighting and other 12v cabin use and
be able to isolate it from the engine starting battery. When it is in need of charging the battery
switch can be set to recharge the battery from the engine.
This is the most common wire installation of a battery switch for a single engine boat. There are
different ways to have a switch configured as well as using more than one switch in a dual engine
install. With this configuration both batteries are grounded to the engine block. The use of one
ground wire to the block from a battery and having a short cable tieing the grounds together between
the two batteries is common practice. The positive leads from each battery connect to the number 1
and 2 posts on back of the switch with the common post attaching to the starter.
There are several different manufacturers of battery switches. The switches are also available with just
an on and off for a one battery setup. Locking battery switches can be had also to help fend off theft or
tampering. Some very common names in battery switches include Guest, Blue Sea, Perko, and Tempo
Note: Blue Water Marine is not liable for damages caused by improper installations or
repairs. The information on these pages are for "information only", not to replace manufacturers
instructions. These pages are meant for helpful knowledge for the do-it-yourself, if you are not
confident in what you are doing please leave the work for the experienced.