Battery (dis)connect?

golfer1john · 11-18-2014, 11:28 AM

We have a switch in the convenience center on the 2012 Montana labeled "battery disconnect". It is in the "on" position, and everything seems to be working fine, whether or not we are plugged in to shore power.

Does "disconnect on" mean the battery is disconnected? Or connected?

It seems to me it is behaving like a "connect switch" not a "disconnect switch".

**hankpage** · 11-18-2014, 11:48 AM

Consider it like the wall switches in your stick home. Switch "ON" let there be light .... Switch "OFF" and your in the dark. Try not to over-think the operations of your RV. They are fairly simple ..... if one way doesn't work .... try the other.

**chuckster57** · 11-18-2014, 01:14 PM

Plugged into shore power bypasses the disconnect. Your 12V stuff will work, but the battery will not charge.

Yosemitebob · 11-21-2014, 11:09 AM

Quote:

Originally Posted by chuckster57

Plugged into shore power bypasses the disconnect. Your 12V stuff will work, but the battery will not charge.

A good point to remember to have that switch "ON" when traveling so your battery gets charged from the TV

instymp · 11-21-2014, 03:09 PM

That is why I wonder why I should turn it off, makes a lot of sense in a boat because of electrolosis problems & accidently bumping into a switch & leaving your running lights on, but in the camper, hooked to shore power, I don't see the urgency.

**JRTJH** · 11-21-2014, 03:23 PM

There probably is no "real urgency". If you're not connected to shore power, turning the battery disconnect "off" could help conserve the battery power. If you're connected to shore power and have any issues with "overcharged" or "dry" (need to add water frequently) batteries, turning the disconnect "off" could make it easier. Generally, I don't turn mine off unless I'm parking the trailer for an extended time without shore power. Otherwise, it's easier to just leave it "connected" (on).

SkiSmuggs · 11-24-2014, 06:57 AM

To me, the main purpose of the battery disconnect is for RV storage while not connected to shore power. The disconnect eliminates parasitic battery drain from the stereo, smoke/CO2 detectors, etc.

Yosemitebob · 11-24-2014, 07:21 AM

Quote:

Originally Posted by SkiSmuggs

To me, the main purpose of the battery disconnect is for RV storage while not connected to shore power. The disconnect eliminates parasitic battery drain from the stereo, smoke/CO2 detectors, etc.

Turning off the manufacture battery disconnect, does not turn off all power. You may still end up with a dead battery, or at least low, depending on how long you leave it stored.

**JRTJH** · 11-24-2014, 07:55 AM

Quote:

Originally Posted by Yosemitebob

Turning off the manufacture battery disconnect, does not turn off all power. You may still end up with a dead battery, or at least low, depending on how long you leave it stored.

That is correct. There are some "parasitic drains" that remain activated even when the "factory installed" battery disconnect switch is turned off.

I installed a second battery disconnect on the negative battery cable. It is connected to the negative terminal between the battery and the ground. When I turn this "second switch" off, the entire battery system shuts down. That way I have maximum storage with no parasitic drains.

**chuckster57** · 11-24-2014, 08:07 AM

John: just askin, is there any advantage to using the negative side instead of the positive side?

Yosemitebob · 11-24-2014, 08:17 AM

Quote:

Originally Posted by chuckster57

John: just askin, is there any advantage to using the negative side instead of the positive side?

Oh Chuck, you had to ask that! It is a matter of opinion. I have my cut out on the positive side, others on the negative side, both are going to do the exact same thing. Now, that being said, I'll leave it to the battery experts.

And before anyone points out that I have exposed terminals, there is clear tool dip on those exposed threads.

**JRTJH** · 11-24-2014, 08:53 AM

Chuck,

That is a good question, but one that's filled with "controversy" based on the application.

Here is a statement from HELLA, one of the manufacturers of disconnect switches: "Hella battery master disconnect switches allow interruption of the main battery cable for effective protection. The positive or negative cables can be switched off as required. The keys can be removed while in the off position and the current is interrupted. Keep your things protected when your not around." So essentially, they say that it doesn't really matter.

It is a NHRA requirement that a battery disconnect switch be installed in an accessible area OUTSIDE the automobile and that it be connected to the POSITIVE terminal of the "contained battery".

In marine applications, there is also a "common practice" to install the disconnect on the POSITIVE terminal. The reason for this is in wet applications, there is a possibility that the battery can find an "alternate ground" and create a hazard. (Imagine being in the water beside your boat and grabbing onto the engine with the battery ground disconnected. There's a chance that if the battery were submerged in the bilge, you could become a part of the battery circuit as it finds a "ground through your body". The same pathway could lead to electrolysis induced corrosion onboard the vessel.

If you think about the application in an RV, other than the positive terminal being "dangerous" (if you happen to touch it and a ground point with a metal tool, you'll get sparks). With the switch on the negative terminal, there's no potential for that to happen.

Also, in the Ford Owner's Manual, the section about storing your vehicle for an extended time states: "It is recommended that the negative battery cable terminal be disconnected from the battery if you plan to store your vehicle for an extended period of time. This will minimize the discharge of your battery during storage."

But really, the bottom line, I think, is that the RV battery be "electrically removed" from the system during extended storage. Whether one chooses to disconnect the POSITIVE or the NEGATIVE terminal (or even both) is more an "personal opinion" rather than an "electrical rule of function".

**chuckster57** · 11-24-2014, 01:31 PM

Wow. That can of worms was enough to go fishing for a week!! I don't do electrical work any more than needed, and having color vision issues I rely on tools.

Thanks for taking the time to explain.

Barbell · 11-24-2014, 02:53 PM

I can only speak for myself and our unit. It is a 2014 Montana. Since new, even with the battery disconnected via the factory disconnect switch, it will discharge the battery in 24 hours. I tried flipping the switch AND a disconnect on the negative side of the battery; same result. Only with disconnects on both battery terminals will the battery hold a charge when stored. The advise to put disconnects on both terminals came from a Keystone tech and it works. He had no more idea why it was discharging the battery than I did but it was a lot cheaper and quicker to put on another disconnect than to try to track down where the drain was coming from.

SkiSmuggs · 11-25-2014, 05:15 AM

Quote:

Originally Posted by Yosemitebob

Turning off the manufacture battery disconnect, does not turn off all power. You may still end up with a dead battery, or at least low, depending on how long you leave it stored.

That is why I keep a Battery Minder on it all winter.

SAABDOCTOR · 11-25-2014, 07:38 AM

NOPE IT IS THAT THE GROUND IS EASIER TO WORK WITH

gearhead · 11-25-2014, 02:54 PM

Quote:

Originally Posted by Barbell

I can only speak for myself and our unit. It is a 2014 Montana. Since new, even with the battery disconnected via the factory disconnect switch, it will discharge the battery in 24 hours. I tried flipping the switch AND a disconnect on the negative side of the battery; same result. Only with disconnects on both battery terminals will the battery hold a charge when stored. The advise to put disconnects on both terminals came from a Keystone tech and it works. He had no more idea why it was discharging the battery than I did but it was a lot cheaper and quicker to put on another disconnect than to try to track down where the drain was coming from.

Something is bad wrong. Do you ever try use the camper where you don't have hookups? The battery should last weeks not hours.
Is it still under warranty? I would have that looked at before you have a serious accident.

Barbell · 11-25-2014, 05:33 PM

The unit has been in two CW shops while in warranty; found nothing at first stop and at second, they replaced the battery, which made absolutely no difference. We only camp where we have shore power. The one time we did not, had to find a second vehicle with jumper cables in order to hook up after only 48 hours. Besides the CW techs, I have been on the phone with Keystone's tech and no one has any idea what the problem is. There have been no issues with either electrical system and we have been on the road with it about 6 of the last 18 months.

**chuckster57** · 11-25-2014, 08:24 PM

Finding out why your battery goes dead in 24 hours shouldn't be that hard. You need an amp meter, and a little time, and some math skills.

Since this thread deals with battery disconnects, and that's not the issue here, maybe a new thread would be better.

Javi · 11-26-2014, 04:08 AM

Current cannot flow out of a battery if there is no ground to complete the circuit. In fact with the ground post disconnected, you can ground the positive post and nothing will happen.

Again for current to flow through a battery there must be a complete circuit. So if you are seeing a current draw from a battery which has the negative terminal disconnected from any external ground then there is a ground through the battery case.

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