Battery Disconnect switch

Kiddydoc

I'm planning to install a battery disconnect switch on my 2014 T@B S Max before heading out for 2 weeks in coastal South Carolina in April from my home in RI.  Any advice/pictures/instructions from anyone who has done their own install?  I'd like to mount it on the battery box itself if possible.  

leenscottfl

I just put one on my battery but went simple and attached it to the negative side battery terminal. May move it eventually but will try it this way.

mawebb

I am planning to put mine inside, mounted between the carbon monoxide sensor and the 110 VAC outlet located under the passenger side seat. It will be installed on the main input lead into the converter as the converter is the distribution and fuse panel for the 12 Volt system. I will be using a marine grade battery switch which far exceeds the current requirements, but will be super reliable. The battery box would be easier but I would prefer to keep the switch out of the elements even though they are rated for wet locations. 

kybob

I'm still learning a lot on this form. What are the advantages of using a battery disconnect? Why do we need one? Thank you!

leenscottfl

I put mine in to totally disconnect the battery. The gas detector, tv and who knows what else uses power all the time, off as well as on. When you don't need any battery power at all you can switch off the battery to conserve power.

mawebb

Unless you disconnect the battery in some way, the carbon monoxide detector, bathroom light, USB charging outlet, radio and TV all draw minimal amounts of power that will drain the battery over time. The quickest way is to remove the fuse that is located on the positive cable off the battery. It is a black rectangular rubberized plastic holder.. You simply pull the top part off and remove the blade style fuse that's inside. As per this discussion, a battery switch is more convenient. 

leenscottfl

There is a youtube video that that explains why you should only put a cutoff switch on the negative terminal. You can pick up a switch like the one with the green knob in the video at Harbor Freight for about $6. It is really simple to do. For the video search youtube for "warning! Automotive battery disconnect switches".

mawebb

Agreeably, if mounting on or by the battery, the ground is the way to go. If installing inside, switching the positive lead going into the converter, is a good method, as long as you ensure the terminals on the switch are appropriately covered to avoid contact with anything that cause a connection to ground. Note that you will also have the protection of the 30 Amp inline fuse that connects to the battery.

TABaker

KarenNGeorge

I installed my first try on the outside nearest to the battery. After forgetting it while in storage, (out of sight, out of mind) I replaced it door side on the front storage box. Now after locking up, the switch is right nearby. Since you'll pass by me in "Low Country" you can see it yourself.

gooselady

TABaker, can you please tell me about the switch in the picture?  Excuse my ignorance.

TABaker

Gooselady, my hubby put that on.  He got the switch at NAPA, and made the diamond plate "shelf" it sits on.  

Mercator

I installed this master/breaker switch when I relocated the 12v battery to the compartment near my Attwood propane heater.  It has a built in 50 amp breaker.  It is located on the driver's (port) bench beside the 110 v outlet.  I started a thread about the battery installation.

Just got back from 8,000 + km trip to Key West FL and the battery (which is held in with wooden cleats) didn't budge. 

mawebb

Finally installed my switch today. I decided to mount it inside the driver side seat bench, on the floor, just next to the power converter. I was going to install it through the plywood face of the bench, but there are several large holes there already. (Power converter, 110 VAC outlet and carbon monoxide sensor. It sits in line on the 10 guage red wire that comes out of the converter as this is the wire that connects to the battery. In this case switching the positive lead makes sense. If you switch at the battery itself, there are safety reasons to switch the negative side.

It's easy to access as I only have to lift the cushion and plywood top to access the switch. The light on the carbon monoxide detector serves as a good indicator that the power is on. I did think about removing the 30 amp fuse from the converter as a means of disconnecting the power, but eventually the fuse holder will wear and possibly fail as they are not designed for that purpose. I will post some pictures when I get a chance. 

Michigan_Mike

leenscottfl said:

There is a youtube video that that explains why you should only put a cutoff switch on the negative terminal. You can pick up a switch like the one with the green knob in the video at Harbor Freight for about $6. It is really simple to do. For the video search youtube for "warning! Automotive battery disconnect switches".

It boils down to "the type of switch used" for this application and where the switch is physically located.  

If you are using a switch that has "exposed metallic parts" (like the switches shown below) and IF it were hooked to a positive terminal then the possibility DOES exist that if accidental or inadvertent contact were made with a grounded surface a fire and short-circuit condition could result.  For the safety reasons noted it is best to hook these style switches to the negative side of the battery.  

The switches shown below are made specifically to mount to the negative battery terminal as the hole diameter is smaller and are designed to mount to the negative terminal of the battery.   

   

mawebb

Here are the photos of my battery disconnect switch. I had to move the negative terminal strip (white wires) to allow room for the switch. I cut the spade lug connectors from the red wire connections and replaced them with captive terminals which are attached to the two posts on the rear of the battery switch. It required a bit of re-dressing the cables but was quite easy to do. I only managed to get three mounting screws to take, as the fourth didn't seem to grab anything and I did not want to use longer screws, without knowing the details of the floor construction.

Kiddydoc

Finally got around to installing the disconnect switch using the same switch noted in TABaker's March 10th post.  I used a different location though settling on the top of the battery box.  I enlarged the sealed vent towards the back of the cover with a dremel tool and top mounted the switch and then fastened it with stainless steel machine screws and washers.  Nice tight surface mount.  To be on the safe side I applied a liberal amount of marine grade clear silicone caulk around the perimeter of the switch for a good seal.  I used a ready made ground cable from walmart for the switch to battery connection and had to replace the terminals on the existing ground wires with larger terminals to fit the switch.  Hot leads were disconnected from the battery during the project.  Took about an hour and works just fine.  The removable key is on a rope fixed to the inside frame of the storage compartment.

jkjenn

I actually have switch from another project I never used, that is identical to Mawebb's. Mawebb, it looks lime you are running both positive and negative wires. From what I have read it is safer to run just the negative. Will that switch work with just the negative? I plan on mounting to the battery box and connecting directly to the battery.

mawebb

I am only switching the positive lead. It's the red wire that runs from the battery into the main input of the converter. Switching the positive is correct when done inside, as I have done mine. When switching at the battery, the negative is safer. This is due to the fact that the switch at the battery could be exposed to metal objects which could create a short to ground. When mounted inside, the switch is enclosed and secured, preventing any potential contact with ground. Also note that you can't disconnect the ground inside as is will stop the converter from being able to continue to supply power to the trailer circuits when the switch is off. The objective of the switch is to only isolate the battery from the trailer when open, not prevent the converter from powering the trailer when on shore power. 

Vjoyce

Would it be OK to just turn everything off in the breaker box?

mawebb

Unfortunately, that won't disconnect the DC (12 Volts), only the 110 V A/C.

There is a 30 amp fuse in the converter, that could be removed to accomplish the same thing, however, I am not sure the fuse socket will stand up well to continuous removal and replacement, resulting in a loose (poor) connection, that will be problematic. I would suggest pulling the 30 amp fuse at the battery instead, as the fuse holder there is inexpensive and easy to replace.

Marceline

I'm finally going to get around to installing a battery cut-off switch now that I've replaced the tub on the front of my trailer. I have a marine cut-off switch that I plan to install similar to how they are now being done in the stock T@Bs. What gauge wire should I use? 

ScottG

@Marceline, I used 10 gauge stranded wire to install my cutoff--that's what is used for the existing line from the battery on my 2015, and what is required to safely carry 30 amps.

Any auto parts store should carry small spools of the stuff.

Marceline

ScottG said:

@Marceline, I used 10 gauge stranded wire to install my cutoff--that's what is used for the existing line from the battery on my 2015, and what is required to safely carry 30 amps.

Any auto parts store should carry small spools of the stuff.

Did you use crimp-on ring connectors or something else?

ScottG

Yes, I used crimp-on ring connectors. They are also available from the auto parts store--make sure you get the ones for the gauge of wire you are using (IIRC the yellow connectors fit 10g). I recommend using a professional-type ratcheting crimper to ensure a solid connection between the connector and the wire.

TerryV6

I am using the same switch that Mawebb is showing.  I followed instructions found on this forum and I mounted it inside the camper.  I cut a hole near the electrical outlet below the drivers side bed.  That way it is easy to get at...

Oldcootcamper

I’m getting a bit of conflicting info regarding the factory installed battery shut off on my new Tab 400

the 2017 manual that came with the Tab says the battery will accept a charge when in the shut off is in the off position.  However I read somewhere else (don’t recall where) that this is not the case.  That the battery doesn’t accept a charge. I emailed NuCamp and they responded that the 2017 manual is wrong and that it won’t accept a charge from solar on the off position.  They recommended keeping the battery in the on position to enable the battery to charge if it’s sunny while outside but not in use. 

I just read read the unofficial manual by awca12 (awesome!) and that says you can charge the  battery with the switch to the off position.  

Anyone know which is correct, or could they both be depending on set up?  Ideally I’d like to fully disconnect the battery from the trailer components to prevent any drain from the Inverter, propane gas detector etc. but still keep the battery charged via solar or shore power. 

Am am I missing something?

thank you

Sharon_is_SAM

The battery cut off switch in the "Off" position isolates the battery from the converter/charger and from any 12 v appliance phantom drain.  It will also isolate the battery from your emergency break-away brakes.  So, if you wish to charge your battery while towing or while on shorepower, and have use of your emergency break-away brakes, leave your battery switch in the "On" position.

The solar charge controller is wired directly to the battery (essentially bypasses the cut off switch) and as a result is not impacted by the battery cut-off switch - so charging will continue regardless of the position of the cut off switch.  So, when it is time to store the trailer in between trips or for a longer duration, you simply fully charge your TaB battery and turn the battery cut  off switch to "Off" and your solar will trickle charge your battery if you wish.

Keep in mind also, that AGM batteries once fully charged and isolated from phantom drain will discharge at an extremely slow rate and may not require use of your solar.  We just picked up our TaB after 6 months of storage and it still read 100% state of charge.  

Also, depending on what kind of battery monitor you have and how it is wired, there may be a very small amperage draw with the battery switch turned off.

ScottG

If in doubt, trace the wires. If the positive wire to or from the device in question passes through the disconnect, then the the disconnect must be "ON" for the device to function. Simple and unequivocal.

There's been a lot of misinformation from various sources about battery cut-offs. Personally, before I believe anything regarding electrical wiring, I like to physically verify it for myself.

However, since I don't have a 400 to inspect, I'll buy what Sharon_is_SAM said above!  :-)

Oldcootcamper

Sharon_is_SAM great point about the break controller.  I would have missed that.  Scott I’ll trace the wires to validate when I install my battery monitor - although it may not be needed since I also have the victron solar charge controller which gives me voltage and that can approximate the SOC I guess