A battery cutoff switch, as the name says, "cuts
off" your battery to isolate it from any loads. There are many possible
reasons to do this, here are three of them.
1. Safety When working on your electrical
system it's a good safety precaution to remove all power. This is
especially true when working on high current components. DC voltage arcs
and burns, it can cause fire, and can burn your flesh easily.
2. Storage In storage, your RV batteries
will discharge quickly if they remain connected to any load at all. In
fact, if stored for a month or more they may still discharge even if
disconnected (that's why many people use a small solar panel to keep them topped
3. Secondary battery bank Say you have
two batteries and you want to add 2 more, but the existing batteries are 2 years
old. Adding 2 new batteries to them (total of 4) isn't a good idea because
the old batteries would drag down the new ones and shorten their life. The
solution is a dual battery switch like the PERKO switch further down the page.
Types of switches
There are basically two types of cutoff switches.
Manual and electric.
Electric switches are cool, but more expensive than
manual ones. Installation of an electric switch is more involved. Most motor homes have an electrically operated
battery cutoff switch. Ours is over the side exit door. Other RV's
may have these, but often a travel trailer has no switch of either type.
Here's a photo of a battery disconnect switch kit.
This one handles up to 250amps continuous (which is plenty).
Manual Switches can be further broken down
into rotary and blade switches. The majority will fall into one of these
two categories. Blade switches are inexpensive, and can be very
functional. Rotary switches are available in more configurations and give
you more flexibility. They will cost from $25 to $90. Here are
photos of several switches.
The first two above are PERCO brand marine grade switches.
These are rated from 250 to 380 amps continuous, and even higher capacities are
available. The switch on the left is a simple
on/off switch, the one on the right allows you to select from one of two battery banks, or
to combine them both. Many boat owners will be familiar with the PERKO switch,
they are very good products. We have one between our batteries and
inverter. You can find them at most boating supply stores, but you'll get
a better price if you "Google" for them. Other good brands are "Guest"
and "Blue Sea".
These two photos are blade switches.
Again the first is a simple on/off, the second allows you to select between two