Battery Disconnect Switch

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CDRGA

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Hello,

I am new to the forum and also new to owning an RV. I purchased a new 2022 Mallard 251BH this past weekend. Everything seemed to be in working order and when I turned the battery disconnect switch to "off", I expected power to be killed to everything (I was not connected to my truck or shore power). However, I was still able to run all of my interior lights and slide/awning as if nothing had been disconnected. I tried turning the switch to the other position, thinking I had perhaps had it turned the wrong way. Still had the same issue. Has anyone experienced this before? Is there an issue with my disconnect switch? And for clarification, what position should this switch be turned to when stored and when connected to shore power?

Thanks in advance for any insight,

Cory
 

Mark_K5LXP

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Someone in engineering, sales or the legal department might have decided that it was "safer" to allow the lights to remain on. Something I would test is if that's the only thing that stays on or if there are other phantom/intentional loads with the disconnect switch turned off. If you measure battery current and it is indeed zero then it just comes down to you making sure both are off when you really want it to be off. Same goes for connection to shore power. When I'm plugged in with the disconnect off my converter is not connected to the batteries and they don't get charged. Sometimes this is intentional, I just want to power house loads with the converter. So a few minutes spent with a meter on the batteries and trying different operating scenarios will answer your questions and you'll know how to work what you have.

Mark B.
Albuquerque, NM
 

NY_Dutch

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Was the RV plugged into shorepower when you tried to disconnect battery power? The 12-volt converter powered by shorepower will keep the 12-volt deices operating even with the batteries disconnected.
 

Rene T

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I would contact the service dept at the dealership and ask them. I have a fifth wheel and I know I can still run my front landing jacks with the switch off but I never went around checking anything else
 

CDRGA

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RV was connected to shore power when I did my walkthrough at the dealership. When I got home, the RV was not connected to anything. I then turned the battery disconnect switch off and was still able to run interior lights, awning, slide, radio, etc. I was just under the impression that if I turned the battery disconnect switch, I would not be able to run those things. So I am concerned that something on the switch was not installed properly.
 

CDRGA

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Thanks Mark. So does what I'm describing sound somewhat normal? Is it perhaps not an issue that I can still run all of this stuff with the battery disconnect switched off?
 

Gary RV_Wizard

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It's typical for slides and jacks to be directly wired to the battery, thus not affected by the disconnect switch. And in a late model motorhome, those are often powered by the chassis battery anyway.

But leaving 12v power to the lights with the disconnect off (and no shore power or tow vehicle connection) is downright strange. Is this a mechanical disconnect switch or does it trigger a relay somewhere? I'm wondering if it is working at all. Does the fridge go off? Can water heater function? Those things also require 12v power for their circuit boards.
 

Gary RV_Wizard

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Thanks Mark. So does what I'm describing sound somewhat normal? Is it perhaps not an issue that I can still run all of this stuff with the battery disconnect switched off?

I think what Mark is suggesting is that "normal" includes having screwball defects right from the factory. And not detected by the dealer in his pre-delivery check-out.
 

CDRGA

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Thanks for the reply, Gary. I am currently at work but can check those things when I get home this afternoon (I had the fridge turned off before I even left the dealership). In regard to possibly triggering a relay somewhere, do you mind elaborating on that a bit more?
 

Larry N.

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And in a late model motorhome, those are often powered by the chassis battery anyway.
Gary, that Mallard is a trailer, or perhaps I misunderstood your post. But I agree that it sounds rather unusual to not have the battery disconnect do much of anything, and there's only the one set of batteries, so no confusion about which set.
 

Mark_K5LXP

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In a loose derivative of Hanlon's razor, don't assume blame for misunderstanding that which is defective by design. With RV's the most logical, practical or effective solution for the user is secondary to the expediency of the builder. In other words, assume it's effed up before thinking you've done something wrong.

Mark B.
Albuquerque, NM
 

Kirk

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I am currently at work but can check those things when I get home this afternoon (I had the fridge turned off before I even left the dealership). In regard to possibly triggering a relay somewhere, do you mind elaborating on that a bit more?
Like Gary, I would be very surprised if your 12V was turned off since the lights still work. The purpose of a battery cutoff switch is to prevent the battery from discharging when the RV is stored. Most of the switches do not actually turn on or off the battery but rather control a relay device that does so because the current to and from a coach battery is high and better controled by a relay and it allows the realy to be near the battery while the switch that controls it is remoteloy loacted. if you can tell us the manufacturer of your battery isolator or possibley post a picture, that would help us to know if it is working properly. A good RV tech at the dealership you bught it from should also be able to answer your questions about the issue. But if your walkthrough was by a salesperson, it is no surprise that they do not know what they are doing.
M3515.1.jpg

This is a picture of the control switch made by Intellitec and it uses a relay (sometimes called a solenoid) device that is near the battery. There are several other brands that would look different, but similar.
 

John From Detroit

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Sounds to me like a defective discounect.
Suspect list
if it's a hard switch with big cables. That's it. all of it.
If it's like the remote switch Kirk posted a photo of. Or a simple Toggle (light duty) as opposed to a "Big Switch" (often with a red handle) Then the suspect list is as follows
Note remote swiches are OFTEN (But alas not always) 3 position Momentary type spring return to center I was going to type the switch designation but that can be confusing. Spring return to center is enough for now

The switch (low but mine failed.. to RECONNECT)
The fuse that feeds the switch (likely a 5 amp one)
The wires (Always suspect)
And the solenoid that actually does the disconnect (Listen for the CLUNK if not CLUNK think higher on this list)
IN my case There was a nice solid CLUNK when i switched to "STORE" (off) but no sound when I switched to "USE" (on)
I disconnected. Pushed both USE and Store (ON and Off) like 100 times each. re-connected and it worked.. NOTE: This is not entierly unexpected still if it works you are lucky.

Alternative would be to pull the fuse.. then punch 100 times both ways.
WHY that worked.. This type of switch has a "Self Cleaning" Feature. if it's tarnished/dirty enough with power applied it won't self clean. but without power. MINE DID.
Oh you might also just disconnect the battery negative cable and operate (The lights should go off) then operate the switch if it clunks one way but not the other.

Then reconnect and see if it works.
I will say that I have a rather good electrical tool box (lmited electronics tool box but everything I need for electrical work.. and more) and did some rather extensive testing before I tried the switch clean procedure.. So I was absolutely sure it was the switch.
 

CharlesinGA

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Big red rotary switch? Either not connected at all, or somehow miswired. Pretty rare for these to go bad. If the switch that controls a relay as Kirk posted above, the relay has two fuses in the relay itself, one for each direction (relay is spring held in either open or closed, driven that way by power) and one of those fuses could be blown. This is the Intellitec relay and the fuses are just above the blue arrows, typical automotive ATO/ATC blade type fuses.

Charles
 

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