Battery Cut Off Switch - are they necessary???

fayliaa · 06-23-2015, 10:04 AM

My trailer sits for several weeks between uses and I usually leave it plugged into shore power. Do I need a battery cut off switch or should I just leave well enough alone? If I do use a cut off, can I unplug it from shore power? I've heard that keeping it plugged in can damage the

. Not very mechanical when it comes to electricity, so I would appreciate your help.

oldmanAZ · 06-23-2015, 10:23 AM

If you have shore power, you will not need a battery cut off switch to disconnect the battery. Your converter will keep the battery charged, your 12v CO alarm, and other 12v stuff (radio) powered up. You should check the battery water periodically to be sure it does not get too low.

If you do install a battery cut off switch, yes you can unplug the shore power.

mike837go · 06-23-2015, 10:24 AM

If you are leaving it plugged in, the a cutoff switch puts you in the "belt and suspenders" class.

The converter's battery charger will keep your battery on Float Charge and keep the parasite loads powered separately.

If the power grid goes down, then your battery will be called upon for the duration of the blackout.

I keep my trailer plugged in while not camping. No cutoff switch.

Old Blue · 06-23-2015, 10:24 AM

I dont have a battery cut off switch as I leave mine pluged into shore power when not in use . If I could not plug into power I would have a battery cut off switch.

gcloss · 06-23-2015, 10:40 AM

In between trips I don't have access to power, so I installed a cut off switch. A simple and inexpensive modification.

cekkk · 06-24-2015, 10:43 AM

Not meaning to hj, but doesn't disconnecting the neg. accomplish the same thing the disconnect switch does?

mike837go · 06-24-2015, 10:53 AM

Quote:

Originally Posted by cekkk

Not meaning to hj, but doesn't disconnecting the neg. accomplish the same thing the disconnect switch does?

It's the other way around. Disconnecting 1 wire disconnects the battery from the RV. Exactly what you want to do when shore power is unavailable and you are not using the RV.

A disconnect switch accomplishes the same thing in a no tools, no mess fashion. And reconnection faster and easier as well.

cekkk · 06-24-2015, 10:56 AM

Thanks, Mike. That's what I meant.

oldmanAZ · 06-24-2015, 11:00 AM

Yes. But, removing and reattaching the battery cable is not as 'quick and clean' usually. Some electronics don't like the intermittent connection when messing with the cables.

cekkk · 06-24-2015, 11:03 AM

I have a disconnect switch but for those who don't and don't want to spend the money, I was thinking that removing a cable would help and it's free.

**Mustang65** · 06-24-2015, 12:21 PM

Quote:

Originally Posted by oldmanAZ

Yes. But, removing and reattaching the battery cable is not as 'quick and clean' usually. Some electronics don't like the intermittent connection when messing with the cables.

He is correct, the low voltage electronics do not like disconnecting the cable as it is not a CLEAN disconnect. While removing the cable, it could have made and brake contact 3 or 4 times for a split second, low voltage circuits do not really like that. Another issue is you may eventually oxidize the connections (if you do not clean them each time) or not tighten them properly and cause additional future issues.

Not sure as to what your reason for disconnecting the battery ground cable is, but to accomplish disconnecting the battery from the TT electronics just pull the main 30 amp fuse by the battery, this isolates the battery from the TT circuits (except the "Break-away" switch which will not drain the battery if it is not activated).

If you intend on doing electrical projects on the TT (like I do), I would recommend a cut off switch, other wise if you are just parking it with out shore power, pull the main 30 amp fuse.

Don

cekkk · 06-24-2015, 12:34 PM

So it's best to first use my disconnect switch and then remove cables to store or replace the battery? I've got a new battery to install. I'd never thought of messing up electronics.

**Mustang65** · 06-24-2015, 12:57 PM

Quote:

Originally Posted by cekkk

So it's best to first use my disconnect switch and then remove cables to store or replace the battery? I've got a new battery to install. I'd never thought of messing up electronics.

If you have a disconnect switch shut that off before disconnecting the battery. If you do not have a disconnect switch pull the main 30 amp fuse by the battery, then disconnect the battery. Either way, if you are plugged into shore power, also disconnect that source of power.

Don

oldmanAZ · 06-24-2015, 01:01 PM

Quote:

Originally Posted by cekkk

So it's best to first use my disconnect switch and then remove cables to store or replace the battery? I've got a new battery to install. I'd never thought of messing up electronics.

If you already have a disconnect switch installed, yes; disconnect there before disconnecting/installing/removing the battery.

It's not that disconnecting/reconnecting at the battery occasionally will cause a problem with the electronics. But for those disconnecting/reconnecting frequently, a disconnect switch is better.

KScamper · 06-24-2015, 01:02 PM

Sorry for the hijack. But, to overly clarify for myself, if we leave stored for a few weeks at a time with no access to 120. In place of installing a disconnect (or until we can) we can just pull the 30 amp fuse to avoid parasitic drain? Am I understanding that correctly? Any downside to doing it that way vs a disconnect switch?

**Mustang65** · 06-24-2015, 01:06 PM

Quote:

Originally Posted by KScamper

Sorry for the hijack. But, to overly clarify for myself, if we leave stored for a few weeks at a time with no access to 120. In place of installing a disconnect (or until we can) we can just pull the 30 amp fuse to avoid parasitic drain? Am I understanding that correctly? Any downside to doing it that way vs a disconnect switch?

Pulling the fuse is fine

Don

Jagiven · 06-24-2015, 01:13 PM

Quote:

Originally Posted by KScamper

Sorry for the hijack. But, to overly clarify for myself, if we leave stored for a few weeks at a time with no access to 120. In place of installing a disconnect (or until we can) we can just pull the 30 amp fuse to avoid parasitic drain? Am I understanding that correctly? Any downside to doing it that way vs a disconnect switch?

Yep, just pull the inline fuse, and it isolates the battery so it cannot be drained from the parasite electronics. This is what I do when I need to. Normally I am connected to shore power while at home.

Subaru297 · 06-24-2015, 01:27 PM

In many cased the 30amp inline fuse you will find is for the tongue jack. Pulling that won't disconnect your trailer.
On our trailer there is a resettable 30amp circuit breaker attached to the front of the TT frame. So disconnecting that fuse (breaker) would involve tools anyway.

I have added a disconnect switch and it works great.

If you are pulling fuses check your trailer to see if it is still getting power or you may come back to a dead battery.

Cheers

KScamper · 06-24-2015, 01:46 PM

Quote:

Originally Posted by Subaru297

In many cased the 30amp inline fuse you will find is for the tongue jack. Pulling that won't disconnect your trailer.
On our trailer there is a resettable 30amp circuit breaker attached to the front of the TT frame. So disconnecting that fuse (breaker) would involve tools anyway.

I have added a disconnect switch and it works great.

If you are pulling fuses check your trailer to see if it is still getting power or you may come back to a dead battery.

Cheers

Good to know. Thanks!

TWP723 · 06-24-2015, 01:56 PM

I just pull the inline fuse. Did it with my pop-up and never had a issue for 13 years. Only replaced the battery once. I kinda steer clear from yanking the cables off the battery. Just because, being in the auto industry, it's a big no-no due to the electronics and programming of modules and processors. Just something I've always avoided.

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