Battery Disconnect Switch

[re-pete]

Hi, I'm new to the forum and a new owner of a 2019 Bullet Ultralite, bunkhouse model.

I'm looking for some advice on connecting a battery master disconnect switch and the best place to do it. What's prompting this is that we keep missing something when we shut up the trailer and thus find the battery drained when we come back. One time is was a mood light inside the dinette awning, another time it was the refrigerator, this last time it was the radio. We know how to shut all of these things off, but invariably we miss something. I was thinking it would just be easier to install a master disconnect switch. It would also come in handy for quickly killing power to work on the 12V system. I've checked my trailer and my owners manual and I haven't found any indication that there already is one.

I'm also thinking I might look into operating it remotely for convenience.

I'm pretty sure I can certainly figure this out, but rather than reinvent the wheel I thought I'd see if anyone with a Bullet Ultralite, or anyone else who monitors the forum, has confronted this already?

Regards,
Pete

[chuckster57]

Battery disconnect can go between the battery and the first connection. Manufacturers will put it on the positive side which is fine, but it seems like there are those that say it is supposed to be on the negative side.

[skids]

I noticed that there were a few negative cables on my Bullet. I opted to connect those to a point on the battery tray (or frame?) and run the cable from there to the disconnect and then to the battery lug.

[LHaven]

There's a battery positive wire that goes to your factory battery disconnect switch (if you have one) and then to your fusebox; then another one that goes to the safety stuff (e.g., CO/propane sensors) that Code says shouldn't get shut off by the factory disconnect switch; then another one goes to your tongue jack; another one goes directly to your breakaway brakes; etc., etc.

Conversely, almost all these devices go to frame ground somewhere and there's typically only ONE cable that goes from frame to battery negative. So that's usually the handiest place to put the One Switch That Controls Them All.

There are a lot of disconnect switches sold for that location. In my opinion, the best are the knife switches, which I don't have room for in my outdoor box -- they have really limited failure modes and they're not rocket science. The disc-shaped rotary ones are popular, but I was dissuaded from buying one of this type due to all the negative reviews in the categories "I can't get it to turn off," "I can't get it to turn on," and (my favorite) "It falls apart and won't go back together."

There's one that's way more expensive than the others because it's "made in USA." I asked the manufacturer what his warranty was, and he said, "It's operational when it leaves the factory." Not only is that the lamest warranty I've ever seen, I haven't found anyone else with a better one.

[re-pete]

Thank for sharing your suggestions, personal experience, technical information and humor. It's all very helpful. I wasn't even thinking about stuff like the electric brakes, and sensors. From a safety stand point and because I definitely could see myself trying to tow it without remembering to reconnect the battery I'll want wire in my disconnect so as to not disconnect the sensors and brakes. With that in mind I'm open to any more information to that end.

Regards,
Pete

[LHaven]

Originally Posted by re-pete

From a safety stand point and because I definitely could see myself trying to tow it without remembering to reconnect the battery I'll want wire in my disconnect so as to not disconnect the sensors and brakes.

It all depends how you envision yourself using it. I'd never tow with any battery disconnect in the disconnect position.

There are two big reasons I'd install a battery mounted disconnect: 1, for safety/reset purposes when I'm working on the coach DC, or 2, for when I leave it for "24 hours" at the dealer for them to do work, which always turns into two+ weeks and a dead battery.

[re-pete]

Originally Posted by LHaven

It all depends how you envision yourself using it. I'd never tow with any battery disconnect in the disconnect position.

There are two big reasons I'd install a battery mounted disconnect: 1, for safety/reset purposes when I'm working on the coach DC, or 2, for when I leave it for "24 hours" at the dealer for them to do work, which always turns into two+ weeks and a dead battery.

Naturally, you're absolutely right about the towing part. And I agree with 1 and 2 as well. However, concerning #2, because I've never owned a brand new RV, I've never had a dealer work on them. I also own an Airstream and master switches are standard in an Airstream and to be honest I never actually paid attention to how mine was wired. If I needed to work on the 12v, I just flipped it off and then back on again when I was finished. Also, different is that my Airstream owners manual has a detailed wiring schematic which comes in handy. I contacted Keystone about getting the wiring schematic for my Bullet and was told that it was proprietary. So, Whan, whaa. ��

Regards,
Pete

[LHaven]

Originally Posted by re-pete

Also, different is that my Airstream owners manual has a detailed wiring schematic which comes in handy. I contacted Keystone about getting the wiring schematic for my Bullet and was told that it was proprietary.

Was there a long pause while they had the phone muted and were rolling on the floor laughing?

Henry Ford would plotz to see certain modern RV factories. No two "identical" units are ever built entirely the same way.

[Texas Steve]

I use one of these type rotary disconnects between the battery negative and the frame ground. It totally disconnects all power from the trailer. When we go to hook up to the trailer its the first thing to turn on and all the safety items and tongue jack is ready to go.

Paid about $30 for the switch and a 2' battery cable from the jungle website.

[re-pete]

Originally Posted by LHaven

Was there a long pause while they had the phone muted and were rolling on the floor laughing?

Hahaha, No, I was speaking to what sounded like a young girl. I'm sure she just reads her answers from a notebook.

Originally Posted by LHaven

Henry Ford would plotz to see certain modern RV factories. No two "identical" units are ever built entirely the same way.

No doubt.

[re-pete]

Originally Posted by Texas Steve

I use one of these type rotary disconnects between the battery negative and the frame ground. It totally disconnects all power from the trailer. When we go to hook up to the trailer its the first thing to turn on and all the safety items and tongue jack is ready to go.

Paid about $30 for the switch and a 2' battery cable from the jungle website.

Thank you. From your picture it looks like you just installed it in the front compartment right behind the battery. Is that about right?

Oops! I just took another look at your picture and realized that it's probably mounted on the exterior above the battery.

Regards,
Pete

[paklein58]

Here's a decent video of a common way to install/mount the battery disconnect switch.

https://www.youtube.com/watch?v=FkPzbRvUctc

[RVPP]

KISS, I mounted my disconnect switch on the outside of my battery box. KISS

Regards, Paul

[harris71]

I encountered a "low-voltage" error trying to raise the Lippert landing gear after the rig sat in storage for about two months, so after charging the battery at home, I added a marine-grade battery disconnect on the positive battery cable. I had the same thing happen a month later so I added a disconnect to the negative battery cable as well. It still didn't solve the problem, so I now pull the battery when it goes into storage for more than a week and keep it on a battery tender. The battery tested fine once it was recharged. I eventually purchased a new battery from an Interstate Battery shop, and in talking with the dealer, he indicated batteries will slowly discharge on their own just sitting on a bench not connected to anything. Based on my experiences, I tend to believe him. If the rig will be sitting for more than a week or two, pull the battery and/or connect it to a Battery Tender.

[Steve d]

Originally Posted by re-pete

Thank for sharing your suggestions, personal experience, technical information and humor. It's all very helpful. I wasn't even thinking about stuff like the electric brakes, and sensors. From a safety stand point and because I definitely could see myself trying to tow it without remembering to reconnect the battery I'll want wire in my disconnect so as to not disconnect the sensors and brakes. With that in mind I'm open to any more information to that end.

Regards,
Pete

if you cant remember to turn on the 12V disconnect switch when hooling up for towing that is a problem. Do you not use anything electric when hooking up your trailer,? ie interior lights wheel jacks ect ?
The only way to 100% disconnect batteries is between neg. battery post and frame period.

[re-pete]

Originally Posted by paklein58

Here's a decent video of a common way to install/mount the battery disconnect switch.

Good video. Of course it sent me down the rabbit hole and I watched about 6 more on installing a battery disconnect switch. I only saw one that used a knife switch, the rest all used the rotary switch. While, I know and like the the infallibility of a good knife switch I also know that space is a real consideration. For that reason, and because I have a 30 plus year old trailer that had a rotary switch (On / Off), that never failed, I'm going to go with that. I also agree with a following post that it should be done on the negative /ground wire to the battery. Something I learned a while back concerning electricity is that electrons actually flow opposite of conventional belief. Conventional belief is that a DC current flows from the positive side of the battery to the load and then back to the negative side of the battery.
In reality negatively charged particles always flow to positively charged particles. Electrons are negatively charged so they actually flow toward the positive side of the battery through a circuit and not the other way around. Regardless, disconnecting the negative terminal is actually safer and definitely effective.
That said, as harris71 pointed out if the battery will be disconnected for an extended period of time then it should be placed on a trickle charger to maintain it's charge and extend it's life. I'm attaching a pretty good video about this.

Save Your RV's Batteries CHEAP & EASY!!

Originally Posted by RVPP

KISS, I mounted my disconnect switch on the outside of my battery box. KISS

Regards, Paul

I totally agree with the KISS principle. In almost all of the "multiple" videos I watched the RV owners did the same thing. While it is definitely the simplest way, the battery box on my Ultralite is tucked up under the front of the trailer. So, I'm I'm going to need to check that out before I make a commitment as to placement. Unfortunately, it's 2.5 to 3 hours from where I live, so that will have to wait until I get there. Probably a couple of weeks from now.

Regards,
Pete

[re-pete]

Originally Posted by harris71

I encountered a "low-voltage" error trying to raise the Lippert landing gear after the rig sat in storage for about two months, so after charging the battery at home, I added a marine-grade battery disconnect on the positive battery cable. I had the same thing happen a month later so I added a disconnect to the negative battery cable as well. It still didn't solve the problem, so I now pull the battery when it goes into storage for more than a week and keep it on a battery tender. The battery tested fine once it was recharged. I eventually purchased a new battery from an Interstate Battery shop, and in talking with the dealer, he indicated batteries will slowly discharge on their own just sitting on a bench not connected to anything. Based on my experiences, I tend to believe him. If the rig will be sitting for more than a week or two, pull the battery and/or connect it to a Battery Tender.

I appreciate that sir. I posted a pretty good video link above concerning this very problem. Thanks for highlighting it.

Originally Posted by Steve d

if you cant remember to turn on the 12V disconnect switch when hooling up for towing that is a problem. Do you not use anything electric when hooking up your trailer,? ie interior lights wheel jacks ect ?
The only way to 100% disconnect batteries is between neg. battery post and frame period.

Yup, no argument. Much different from this new to me trailer my old trailer also had solar. I never bothered to disconnect my battery when it was idle because it was continually being charged when the sun was out. Not so with the Bullet and since it's pretty much going to sit right where it is a very tree covered location. Solar would be of little advantage. So, I momentarily was not thinking about several things. Most correctly, as you pointed out, that if I disconnect the 12vdc power then nothing, including the electric jack operates until I reconnect the power. So, forgetfulness or not, that alone would remind me.

Also, you point out, using the negative side for the disconnect is absolutely the best way.

Regards,
Pete