Battery disconnect switch purpose on Momentum

[CaliMClass]

Some will know from my other posts that I’ve just replaced all my house batteries due to the old ones being ruined by the previous owner.

I’d really like to save these new ones from a similar fate, but I realize I’m not fully understanding the purpose of the battery disconnect key in the basement.

When should it be on ( batteries disconnected ), when should it be off ( batteries supplying power to the trailer )?

My understanding is that it should only be off when there is no shore power available to do things like raise / lower jacks and run a few lights if needed. If we have shore power we can just leave the disconnect on ( batteries supplying no power to trailer ). Is this right?

Also, I notice that turning the key anti clockwise from the ON position ( to about 10 o clock ) allows the key to come out...any purpose or advantage to this?

Thanks in advance for this, and apologies if they’re obvious questions, I just want to be careful with my new batteries. [emoji4]


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[bertschb]

I can answer some of your questions. If you can remove the red key (handle), your batteries are mostly disconnected. There is still some parasitic drain on the batteries in this case which is how people get into trouble. They remove the red handle thinking their batteries are disconnected only to come back a month later and find out their batteries are dead. It's a poor design that I wish RV manufacturers would change.

If you plan to store your trailer for more than a week or two, I would recommend removing either the negative or positive battery cable from your RV. This will truly disconnect your batteries. You can store your RV like this for several months without damaging your batteries.

[FT4NOW]

In reality, you never need to operate that switch since it leaves some loads still connected and will drain your battery. If you are disconnecting for storage you either want to install a true disconnect switch or remove one of the battery terminals. If you install your own disconnect it should be immediately after the battery before any loads. I'm not sure of the purpose of the factory disconnect since there are still parasitic loads. The key comes out so it cant be turned back on by accident , or possibly for security so the landing gear cant be operated, but that depends how GD wired your particular unit.

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[CaliMClass]

In reality, you never need to operate that switch since it leaves some loads still connected and will drain your battery. If you are disconnecting for storage you either want to install a true disconnect switch or remove one of the battery terminals. If you install your own disconnect it should be immediately after the battery before any loads. I'm not sure of the purpose of the factory disconnect since there are still parasitic loads. The key comes out so it cant be turned back on by accident , or possibly for security so the landing gear cant be operated, but that depends how GD wired your particular unit.

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This is helpful, thank you. My plan is to remove the negative cable to the trailer when storing for more than a couple of weeks ( as a helpful poster on this forum suggested ).

So sounds like, I can leave this disconnect with the key out all the time, unless I don’t have shore power available to get jacks up/down ( which is very rare )?

Thanks as always!


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[JCR GD]

So sounds like, I can leave this disconnect with the key out all the time, unless I don’t have shore power available to get jacks up/down ( which is very rare )?

No, if the key comes out, the batteries are disconnected. The Batts will not charge. Just leave the key in and turned so batts provide power and leave it alone. When storing just disconnect neg cable on batt.

[CaliMClass]

No, if the key comes out, the batteries are disconnected. The Batts will not charge. Just leave the key in and turned so batts provide power and leave it alone. When storing just disconnect neg cable on batt.

Ah ha! Ok. Got it. When the trailer is in use, disconnect key should be in the OFF position the whole time ( batteries providing power to trailer ). When parked in storage, trailer negative cable should be disconnected.

I guess one last question...when connected to the truck on travel days...disconnect key off ( battery power to trailer ), or on ( no battery power to trailer )?

I can’t say how much I appreciate the help. I’m really gunshy of ruining these batteries, my wallet isn’t ready for another hit like that. [emoji4]


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[JCR GD]

Ah ha! Ok. Got it. When the trailer is in use, disconnect key should be in the OFF position the whole time ( batteries providing power to trailer ). When parked in storage, trailer negative cable should be disconnected.

I guess one last question...when connected to the truck on travel days...disconnect key off ( battery power to trailer ), or on ( no battery power to trailer )?

I can’t say how much I appreciate the help. I’m really gunshy of ruining these batteries, my wallet isn’t ready for another hit like that. [emoji4]


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You never need to touch the key

[bertschb]

The easiest thing to remember is to just leave the red key in all the time and disconnect the battery cable for storage. Don't over think it :-)

[CaliMClass]

THANK YOU!

Going out to the basement now ( camping by the ocean here in Monterey, CA ). Setting the key to OFF ( batteries supplying power to trailer ), and will leave it like this until we get it back to storage, at which time I’ll disconnect the neg cable from the trailer.

NEVER TOUCHING THE KEY AGAIN NOW. [emoji51][emoji2]


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[boyscout]

NEVER TOUCHING THE KEY AGAIN NOW. [emoji51][emoji2]

Good plan, thx to the others who responded. I'll add a couple of wrinkles.

First, you said above that you'd disconnect the battery cable "when storing for more than a couple of weeks". If you had just one 12V battery as most trailers do when delivered, that would be enough time to kill the battery. The parasitic draws that slowly drain the battery vary, but a rough rule of thumb is about 2 amps per hour, twenty-four hours per day... simple math to figure out how long your battery will last.

Since IIRC you have more battery, leaving them connected probably won't kill them in a couple of weeks but it will drain them needlessly. Batteries have a finite number of charge/discharge cycles - no point in wasting them - so you might consider disconnecting yours whenever leaving the trailer for more than a few days.

The second consideration is to touch that untouchable key one more time, when you replace it with a better battery switch and/or re-wire that one to completely disconnect your batteries. No more bending over in the dark cramped front compartment with a wrench undoing battery connections. Simply turn the switch in the basement and the batteries are fully disconnected.

Some people simply re-wire the OEM battery switch to do that job. Others of us have installed one of the switches from Blue Sea Systems:

https://www.bluesea.com/products/9001e/e-Series_Selector_Battery_Switch

These switches are REALLY well-made, smooth and sure, no arcing, no key to fall out.

The one I linked is rated for 350 amps and has some flexibility to turn on either one or both of two batteries or banks of batteries. Other switches from the company handle just one battery/bank, but there's no downside (other than possible future brain farts) to using the two-bank switch for one bank.

Sure, replacing or rewiring the switch is a bit more ambitious but it's not a gargantuan task. Some battery cable and terminal ends, maybe a nice new switch, and an hour or two of puttering and you'll have a Better Life.

Good luck.