Miscellaneous Electrical Topics

Read This First: Disclaimer. I've written what I personally did, and my opinions. Don't assume what I did was safe, and don't assume it will work for you. Do more research, and make your own choices. I am not responsible for your outcomes! :-)

After writing RV Electric Power for Dry Camping, I realized that there were a few topics I hadn't covered. As I browsed online forums answering questions several things continued to come up, so I decided to start including answers here for the frequent ones. I'll add them as we go.

Battery Cutoff Switches

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 off).

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 battery banks.