Battery disconnect - Montana Owners Club

JeffZ · 01-25-2022, 10:23 AM

Our coach has 2 battery disconnect switches. We justbfried a battery and can't find any information on how to use them. I know that in the off position the batteries will receive their charge from shore power and when connected to the truck.

I, however, have no idea which one need to be off and or on and when they should be on those positions.

We are full time in our montana 3855br and everytime I get to the next spot there is not enough voltage to extend the leveling system. We don't ever store it so we need the batteries to always have a good charge.

Any help would be appreciated

**DQDick** · 01-25-2022, 10:33 AM

First, let me state that all of our Monty's have only had one battery disconnect and even in the off position the batteries will still be killed by things like the propane detector that are direct wired. So the only real way to disconnect the batteries completely is to remove the ground wire from the battery. If you can remove the key then shore power won't charge your battery, but it will still discharge as stated above. My guess on the other switch is that it disconnects power to your inverter if you have a residential fridge or it could be a transfer switch for use with a generator.

JeffZ · 01-25-2022, 10:40 AM

The one by the batteries has 3 positions on, off, and actuator out. The key by the water hookup has only 2 on and off.

With that being said. The one by the water supply I have in the off position. Does that charge my batteries when I am disconnected?

And the one by the batteries I do believe is for the inverter. I have that in the on position until I move the coach then I turn it off and the inverter comes on.

Does this sound correct to your knowledge.

We have been full time for a year and this is the first time I've had confusion about the batteries. Sulfur filled the rv and scared the **** out of us.

**AZ Traveler** · 01-25-2022, 10:49 AM

Jeff,

Since you full time. I would expect your would always keep your battery switches connected. If your batteries are disconnected they will not charge.

If you ever store your rig, recommend you disconnect the negative battery terminal.

**Carl n Susan** · 01-25-2022, 12:05 PM

It help immensely if you tell us the year and model of your RV. That said it appears you have the "normal" battery disconnect in the convenience center and an additional battery disconnect for the inverter (that feeds the residential refer or whatever) in the battery compartment.

For the battery disconnect switch in the convenience center, the best thing to do, especially if you are a full timer, is to leave the Red Key in the position where is *CAN NOT* be removed. The labeling is confusing and the On/Off positions don't help. The battery is only charged when the Red Key is in the position where it can't be removed.

As for the battery disconnect for the inverter, it too should always be on. That way the inverter automatically kicks in if you lose power at the park or when you unplug to move. The rest of the time the 12V side of the inverter is in standby mode.

JeffZ · 01-25-2022, 12:11 PM

Thank you so much for the information. It is a 2020 montana 3855br.

I now know what positions the "switches" need to be in.

Super appreciative for this group

jdarwin · 01-26-2022, 10:45 AM

Quote:

Originally Posted by JeffZ

Thank you so much for the information. It is a 2020 montana 3855br.

I now know what positions the "switches" need to be in.

Super appreciative for this group

Welcome to the group Jeff. If you have a residential fridge (we do) there is another switch in the battery bay to turn off power to it. That said, you will have parasitic drain even with the convenience center key removed. The only way to kill all battery power to the coach is to install a kill switch at the battery.

Camp CA · 01-26-2022, 08:49 PM

Suggest a battery disconnect switch installed at the battery independent of the trailer's batter on/off switch to mitigate battery going dead.

Mikelff · 01-30-2022, 02:45 PM

If you smelled strong sulphur smell you may have fried your batteries. I would suggest you pull them and have them load tested. If you have two batteries and one is fried, you need to change out both batteries.

DebNJim B · 02-02-2022, 06:36 PM

Quote:

Originally Posted by Carl n Susan

It help immensely if you tell us the year and model of your RV. That said it appears you have the "normal" battery disconnect in the convenience center and an additional battery disconnect for the inverter (that feeds the residential refer or whatever) in the battery compartment.

For the battery disconnect switch in the convenience center, the best thing to do, especially if you are a full timer, is to leave the Red Key in the position where is *CAN NOT* be removed. The labeling is confusing and the On/Off positions don't help. The battery is only charged when the Red Key is in the position where it can't be removed.

As for the battery disconnect for the inverter, it too should always be on. That way the inverter automatically kicks in if you lose power at the park or when you unplug to move. The rest of the time the 12V side of the inverter is in standby mode.

All correct. Just to add to this if the switch in the forward compartment is off it will also not allow the batteries to charge.

I have never turned mine off in four years. There is no reason to. As was stated if you want to disconnect for storage, it's best to put a switch on the negative side or just remove that cable.

**Carl n Susan** · 02-02-2022, 07:24 PM

Quote:

Originally Posted by DebNJim B

....Just to add to this if the switch in the forward compartment is off it will also not allow the batteries to charge...

I don't think so. The disconnect switch in the forward compartment (where the batteries are located) for the power to the inverter has no effect on the battery being charged or not. It only draws power from the batteries. The converter charges the batteries via the separate line through the 50 amp self resetting circuit breakers. The disconnect switch in the convenience center does however affect the charging of the batteries

DebNJim B · 02-03-2022, 04:51 AM

Carl, I would agree with what you stated, however, this is my experience.
When I first brought our rig home, I had it in the driveway on shore power while I got it set up for travel. I took delivery with a damaged cabinet door as they had one on order and when it came in they sent a tech up to install it at my home.
While he was there I showed him that I had been trying to run the fridge on battery without success. He told me the battery was too low to run the inverter and it was because that switch was off. He turned it back on the told me to always keep it on. Sure enough after a couple hours the battery was back up enough that when I disconnected shore power the fridge stayed one.
Didn't make sense to me at the time and it still doesn't, but that's how it went.

ChuckS · 02-03-2022, 06:59 AM

Rather then guessing if the second battery disconnect switch does or doesn't affect the ability of the inverter battery to charge why not just use your multimeter ...

A quick check with shore power applied and that inverter battery cutoff switch in the OFF position will tell you...

If you see 13.4 volts or better with inverter battery cutoff switch OFF then you know it only affects the 12 volt DC supply to the inverter...

If however you read less than 13.2 volts at that battery with its cutoff switch OFF then you know it DOES affect the charging of the battery..

Either way that battery is the front for the inverter is still in parallel with the main 12 volt DC BUS and will be affected via current draw if no shore power is available UNLESS a battery isolator is installed....

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