Installing a manual battery disconnect switch

Ericb760 · April 13, 2020, 05:22 PM

With the weather warming up here in the Cali desert my wife put her foot down by proclaiming that we were not going to spend the summer living in the RV. Ok, so we got a little place for the season as we go forward in building a house on our land, which is where the RV is parked. I had to meet with a grading contractor this weekend, so I opened up the RV to start it. I had installed a new chassis battery two months ago that solved a lot of my electrical problems. This time the battery was dead. Nor could I use the house batteries to start the engine. I realize that I must have a small drain on the battery. I just can't figure out what it is. Anyways, I want to install a battery disconnect switch so I can turn everything off while it is not being used. Anyone have any experience with adding this appliance? I am considering this one:

https://www.walmart.com/ip/ATV-RV-Waterproof-On-Off-Auto-Vehicle-Isolator-Disconnect-Marine-24V-12V-Battery-Truck-Kill-6V-Removable-200-1000-Switch-Key-Master-Switch-Car-Cutoff/116162091

Rickf1985 · April 13, 2020, 05:46 PM

Not much to it, you disconnect one of the battery cables, I use the ground side, and hook it to one side of that switch and then run another cable from the other side of the switch back to the battery terminal you took the cable off of. You can use the ground or positive side, I use the ground side for the main reason it you have two bare terminals open there and if you short them against something on the ground side nothing happens, it it is on the positive side you will let out a whole lot of the magic smoke!!!!! Most of those switches are designed to go through a hole and have the wires on one side and the switch on the other so pick a spot where you can drill the hole. Or, you can get something as simple as this.
https://www.harborfreight.com/battery-disconnect-switch-97853.html?cid=paid_google|*PLA+-+All+Products|All+Products|97853&utm_source=google&utm_medium=cpc&utm_campaign=*PLA+-+All+Products&utm_content=All+Products&gclid=Cj0KCQjwm9D0BRCMARIsAIfvfIbBjkfQfwupwnjrNboF5vgMDnPiL_YpNwLgPYDBKqIrRZ8mEMfPJbIaAg9tEALw_wcB

Ericb760 · April 13, 2020, 10:07 PM

Quote from: Rickf1985 on April 13, 2020, 05:46 PM
Not much to it, you disconnect one of the battery cables, I use the ground side, and hook it to one side of that switch and then run another cable from the other side of the switch back to the battery terminal you took the cable off of. You can use the ground or positive side, I use the ground side for the main reason it you have two bare terminals open there and if you short them against something on the ground side nothing happens, it it is on the positive side you will let out a whole lot of the magic smoke!!!!! Most of those switches are designed to go through a hole and have the wires on one side and the switch on the other so pick a spot where you can drill the hole. Or, you can get something as simple as this.
https://www.harborfreight.com/battery-disconnect-switch-97853.html?cid=paid_google|*PLA+-+All+Products|All+Products|97853&utm_source=google&utm_medium=cpc&utm_campaign=*PLA+-+All+Products&utm_content=All+Products&gclid=Cj0KCQjwm9D0BRCMARIsAIfvfIbBjkfQfwupwnjrNboF5vgMDnPiL_YpNwLgPYDBKqIrRZ8mEMfPJbIaAg9tEALw_wcB

I looked at the Amazon version of that one. People were reporting amperage leaking through it causing battery drain. Kind of defeats the purpose...I went ahead and ordered the Walmart version, which on Amazon was twice the price. My chassis battery sits exposed on a tray in front of the engine, probably much like yours does. I may end up buying some sort of battery box so that I have somewhere to mount it.

Rickf1985 · April 14, 2020, 08:26 AM

People were reporting amperage leaking through it causing battery drain

If you are talking about the one I showed with the green knob that would be impossible since with the knob off the wires are separated! No way power can travel across air to get back to the battery to cause a drain. But whatever, it is easy enough to check the one you are getting with a voltmeter to be sure it is dead when turned off. If I were going to buy a high amperage switch for an RV I would go with a brand name marine unit just because it is high quality and I know it is not going to fail on me at the worst time. Electrical failures in high amperage switches can be catastrophic.

Ericb760 · April 14, 2020, 05:24 PM

Quote from: Rickf1985 on April 14, 2020, 08:26 AM
People were reporting amperage leaking through it causing battery drain

If you are talking about the one I showed with the green knob that would be impossible since with the knob off the wires are separated! No way power can travel across air to get back to the battery to cause a drain. But whatever, it is easy enough to check the one you are getting with a voltmeter to be sure it is dead when turned off. If I were going to buy a high amperage switch for an RV I would go with a brand name marine unit just because it is high quality and I know it is not going to fail on me at the worst time. Electrical failures in high amperage switches can be catastrophic.

My construction costs are a bottomless pit at the moment so I'm going to go cheap for now. I will post my observations once I receive it.

Ericb760 · May 11, 2020, 08:44 PM

Quote from: Rickf1985 on April 14, 2020, 08:26 AM
People were reporting amperage leaking through it causing battery drain

If you are talking about the one I showed with the green knob that would be impossible since with the knob off the wires are separated! No way power can travel across air to get back to the battery to cause a drain. But whatever, it is easy enough to check the one you are getting with a voltmeter to be sure it is dead when turned off. If I were going to buy a high amperage switch for an RV I would go with a brand name marine unit just because it is high quality and I know it is not going to fail on me at the worst time. Electrical failures in high amperage switches can be catastrophic.

I ended up buying the one you recommended for the RV and installed the one I bought at Walmart on my wife's truck. The installation process required me to be on my back under the RV while hoisting the battery into the tray. Not fun. Then it was as simple as you described. FYI, I found out what was draining my battery. The PO had installed aftermarket LED lights on the front bumper, and they wired them to the neg side of the battery. That's fine except that the control button in the cockpit has a light in it. Red for off, green for on. While fiddling with my disconnect install I noticed that the red light was on even with the key out of the ignition. I made sure to move the power supply wire from the battery post to the other side of the disconnect. Voltage on the hot side read 12.6, and 0 on the other side with the switch disconnected. Hopefully this solves my problem.

Rickf1985 · May 12, 2020, 10:19 AM

So your battery is dead center in front behind the bumper? That is where mine is but they mad a custom tray fot it so I was not sure that was the original place for it. Yea, getting a battery in there is painful! And I have to do it again on mine.

Ericb760 · May 12, 2020, 11:59 AM

Quote from: Rickf1985 on May 12, 2020, 10:19 AM
So your battery is dead center in front behind the bumper? That is where mine is but they mad a custom tray fot it so I was not sure that was the original place for it. Yea, getting a battery in there is painful! And I have to do it again on mine.

It's slightly off dead center, but still a PIA to get in. I ended up using a ratchet strap to lower the battery down from the top. Use the hook on the strap to hook on to the battery handle. Much simpler than having to lift it in to place.