Adding a battery disconnect

[blubuckaroo]

I normally remove our batteries for the off season and keep them on a Battery Tender, but during other periods of non-use I've been disconnecting the the batteries from the post.
I'd like to add a battery disconnect, since our Passport didn't qualify for such an extravagance.
I've looked at some different types, and some require a hole cut into the chassis to mount the switch, and I won't do that.
What are my options?

[chuckster57]

This one is very popular and I have installed countless number of them.

https://www.walmart.com/ip/MARINCO-7...98a2a5054a4ce0

Argument is positive or negative lead...Manufacturer uses the positive.

[JRTJH]

If you want a "simple and easy to install" BCO switch, Harbor Freight sells a switch that mounts on either the positive or negative battery terminal with the switch built into it. Remove the battery cable, install the device, attach the battery cable to the device and operate the switch. It's $6.99 at HF https://www.harborfreight.com/batter...tch-97853.html

If you get into the argument of "positive or negative" and where to install it, just buy two ($14) and install one on each terminal on the battery.....

HF also sells the "red key type" BCO switch for $7. If you decide to go that route, you'll also need to buy a "gray plastic utility box" and an extra battery cable (or cut your current one and solder/crimp terminals on the cut ends). Then you'll need to locate a place to install the box with the BCO switch in it. That location could be "on the battery box lid" or close to the battery location.

It's easier to just install the "battery terminal device", then as you use it, determine if it is "fancy enough for you" or whether you want to indulge in a more elaborate BCO switch system. The total investment is $7 and about 10 minutes.

[Weldon]

Thank you for this. I've been disconnecting our cables after every use. Didn't realize there were options on the market.

[rhagfo]

Originally Posted by chuckster57

This one is very popular and I have installed countless number of them.

https://www.walmart.com/ip/MARINCO-7...98a2a5054a4ce0

Argument is positive or negative lead...Manufacturer uses the positive.

X2
This is the switch I installed on our 5er, and loved it would flip to off when we got home from a trip, and two months later batteries still showed a full charge.

[Javi]

The reasoning behind using the negative post for the cutoff is simple... no ground / no power flow...

If you choose the positive post just be sure to put the switch before any connection to a terminal. This is why there are parasitic draws even with the factory installed cutoff switches.. by law they cannot completely disconnect power from some safety features.

[LewisB]

Also, obviously, if you use the "battery terminal post" type switch and you have multiple batteries, you will need to install the post switch at every battery.

[chuckster57]

Originally Posted by LewisB

Also, obviously, if you use the "battery terminal post" type switch and you have multiple batteries, you will need to install the post switch at every battery.

Not really, just the lead to the trailer if all your doing is disconnecting the "trailer".

[travelin texans]

Originally Posted by LewisB

Also, obviously, if you use the "battery terminal post" type switch and you have multiple batteries, you will need to install the post switch at every battery.

NOPE! Just the primary positive to the trailer or the negative cable going to ground.

[travelin texans]

Originally Posted by LewisB

Also, obviously, if you use the "battery terminal post" type switch and you have multiple batteries, you will need to install the post switch at every battery.

NOPE! Just the primary positive to the trailer or the negative cable going to ground.
If you use the disconnect that separates in the middle & install it on the positive cable you will have sparks, on negative you shouldn't.

[LewisB]

Right. No need to install one on the tow vehicle or the DW's car. Batteries for a residential fridge need special consideration - there's probably other scenarios where separate batteries are used for boondocking or starting the generator. I assumed that we were talking about standard trailer batteries connected to the trailer.

It is fairly common to find 2 or more batteries in a bank that can not be fully interrupted with the OE "disconnect" system. If you have a trailer with more than one battery connected as a bank that you want to disconnect and you choose to use the battery post connection/switch shown by John in his post, then you will need to install a switch on each trailer battery. Sorry if that wasn't clear.

[chuckster57]

Originally Posted by LewisB

Right. No need to install one on the tow vehicle or the DW's car. Batteries for a residential fridge need special consideration - there's probably other scenarios where separate batteries are used for boondocking or starting the generator. I assumed that we were talking about standard trailer batteries connected to the trailer.

It is fairly common to find 2 or more batteries in a bank that can not be fully interrupted with the OE "disconnect" system. If you have a trailer with more than one battery connected as a bank that you want to disconnect and you choose to use the battery post connection/switch shown by John in his post, then you will need to install a switch on each trailer battery. Sorry if that wasn't clear.

Unless you have separate battery(s) for a residential fridge, then again you only need one disconnect at the power FEED TO THE TRAILER no matter how many batteries are in that "bank"

[LewisB]

Originally Posted by chuckster57

Unless you have separate battery(s) for a residential fridge, then again you only need one disconnect at the power FEED TO THE TRAILER no matter how many batteries are in that "bank"

Ok, didn't mean to highjack the thread over the issue. Since you seem determined to ignore what I actually say I'll just hope that others will actually read what I wrote and capture what I was saying. This was not a recommendation on my part. I too would choose a single switch to interrupt the negative side of the entire power feed. My point was simply that you can't use a "post switch" and interrupt only one battery in a bank and expect that to accomplish a complete disconnect. With that, I'm done.

[blubuckaroo]

Thanks everyone. I’m going with the post style. The funny thing is, I first went to NAPA and they wanted $46 for one that looked just like the one at Horror Freight for $7. So I bought two from HF. The other I’ll use on my smaller hunting trailer.I figure these are probably made to handle a starter load. My little travel trailer won have near that load.

[JRTJH]

Originally Posted by blubuckaroo

Thanks everyone. I’m going with the post style. The funny thing is, I first went to NAPA and they wanted $46 for one that looked just like the one at Horror Freight for $7. So I bought two from HF. The other I’ll use on my smaller hunting trailer.I figure these are probably made to handle a starter load. My little travel trailer won have near that load.

According to the HF website, the "terminal mounted BCO switch is rated @12 volts, 500 peak/125 continuous amps. A 6 gauge battery cable 2' long will burn up (or melt the insulation) at around 150-200 amps. If you think about the two mini-breakers on the bulkhead crossmember on your trailer, one is 40 amps and the other is 30 amps, so the max that could ever go through the battery cable (and the BCO switch) is 70 amps. That is, unless you wind up with a direct short on the battery cable, and then, you'd be better off if that switch "burned up quicker than the trailer.....

[Urbish]

A simple reminder for all involved that your RV battery is likely providing power to your trailer brakes in the event of a trailer separation that involves pulling your emergency cable. If your battery is manually disconnected when you are towing (by switch, terminal removal, whatever), your brakes won't set in a separation. So make sure that battery is connected before you tow!

[Customer1]

The reason to switch the positive in any towable is to avoid disabling the breakaway braking system. The breakaway switch is connected to power prior to the disconnect allowing the breakaway to operate regardless of switch position.

[travelin texans]

Originally Posted by Customer1

The reason to switch the positive in any towable is to avoid disabling the breakaway braking system. The breakaway switch is connected to power prior to the disconnect allowing the breakaway to operate regardless of switch position.

But to totally disconnect ALL parasitic drains you need to disconnect a battery cable, by doing this you disconnect the breakaway power.

[skids]

Originally Posted by travelin texans

But to totally disconnect ALL parasitic drains you need to disconnect a battery cable, by doing this you disconnect the breakaway power.

Fortunately, a lot of campers will want to keep the contents of the refrigerator cold, thereby switching on the battery (and the propane).

[rhagfo]

Originally Posted by Customer1

The reason to switch the positive in any towable is to avoid disabling the breakaway braking system. The breakaway switch is connected to power prior to the disconnect allowing the breakaway to operate regardless of switch position.

Well if the disconnect is on the negative cable the breakaway will not work as the battery is not grounded, therefore no voltage.

If you really worry about the breakaway, take the positive wire and attach directly to the battery positive post, the breakaway switch is normally open and will NOT create parasitic draw on the battery.