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Old 09-14-2006, 09:10 AM   #1
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Question Battery Cutoff Swithes

I'm planning on installing the copper cutoffs for my engine battery and the coach batteries. The question is; do I need to put a switch on the positive AND negative terminals, or is switching just one side enough? I know this will come as as stupid question to some, but I'm learning .

Appreciate any help with this.
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Old 09-14-2006, 09:37 AM   #2
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My rig has cut off switches on the positive only. The negatives are grounded to the chassis.

If there is a reason to switch the grounds, I'd be very surprised.

Dickinson, ND
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Old 09-14-2006, 09:39 AM   #3
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Tim
I have a 1988 Classic 290 MoHo. It has a slide out tray with two coach batterys and one engine battery. Even though your MoHo is one year newer and a Ford, you probably have the same battery arangement. If you open the slide out all the way, you should find a factory installed switch for the coach batterys-----mine does. If it does--then I would switch the engine battery the same way.

Hope this helps---Bob
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Old 09-14-2006, 09:42 AM   #4
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Quote:
Originally Posted by guy99
My rig has cut off switches on the positive only. The negatives are grounded to the chassis.

If there is a reason to switch the grounds, I'd be very surprised.

Dickinson, ND
Thanks. That was my suspicion, but I wanted to be sure. I have the cut-off buttons on the inside wall near the door, but they don't seem to work, and the isolators click, but all the batteries charge and discharge at the same time. Rather than trying to figure out how this thing was rewired by the PO I decided this switching was the easiest way to have complete control over what gets cut off, and what doesn't.
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Old 09-14-2006, 10:11 AM   #5
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Tim,
You seem like a very careful fellow so I imagine this comment is not needed. But for the benefit of the knowledge base I want to mention that these batteries hold a lot of energy and one must be very careful with sizing and routing the connections from the battery bank. These batteries can easily 'weld' a hot wire to a ground and can also start fires. Since there not usually any fuses or circuit breakers between the battery and the main distribution terminal one must be very careful.

When I got my rig, the battery wiring was a mess. Opening and closing the battery drawer would often cause shorts to ground!
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Old 09-14-2006, 10:22 AM   #6
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Quote:
Originally Posted by wascobob
Tim
I have a 1988 Classic 290 MoHo. It has a slide out tray with two coach batterys and one engine battery. Even though your MoHo is one year newer and a Ford, you probably have the same battery arangement. If you open the slide out all the way, you should find a factory installed switch for the coach batterys-----mine does. If it does--then I would switch the engine battery the same way.

Hope this helps---Bob
Bob,

We do have the same setup for the tray and the batteries, but I do not have a switch on the coach batteries. They are switched by an inside switch on the wall by the door that goes to an isolator solenoid under the coach. I have another switch for the starting battery with its own solenoid as well - same setup. I know the coach switch and isolator work, but I'm not certain the starting battery switches off. I'm going to test that for a few days. If it's working also, I suppose I really don't need the manual switches at all.

Thanks for the info.
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Old 09-14-2006, 10:27 AM   #7
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Quote:
Originally Posted by guy99
Tim,
You seem like a very careful fellow so I imagine this comment is not needed. But for the benefit of the knowledge base I want to mention that these batteries hold a lot of energy and one must be very careful with sizing and routing the connections from the battery bank. These batteries can easily 'weld' a hot wire to a ground and can also start fires. Since there not usually any fuses or circuit breakers between the battery and the main distribution terminal one must be very careful.

When I got my rig, the battery wiring was a mess. Opening and closing the battery drawer would often cause shorts to ground!
Thanks for the warning. I was fortunate with this MoHo, in that the entire battery wiring, solenoids, and connections had been completely redone just before I got it. All appears to be done correctly, and the shop that installed my Gear Vendors unit several weeks ago verified it was a well-done wiring job. At least one thing on this Blimp was done correctly . Thanks again for the info.
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Old 09-21-2006, 05:02 AM   #8
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Hi Tim; Switches are on the positive wires only. If you have dual batteries you can install a dual batt. switch. Be sure that the continuos amp rating is sufficient to meet your starters amp. draw at cranking. With dual battery make sure that the switch has alternator field disconnect feature, or else you can only switch batteries while engine is not running. Without that feature you will need a new alternator after first switchover. "boatdoc"
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Old 09-21-2006, 07:47 AM   #9
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Tim,
If you already have the remote switches then I would recommend that you consider getting them to work the way you want rather than installing mechanical switches in the battery compartment.

I have the original factory cutoff and an additional West Marine cutoff for the chassis battery (positive only). I turn mine on and off whenever the coach is not in use. I know this sounds lazy on my part but quite honestly it's become a bit of a pain to unlock the drawer, open it, turn them on/off close, etc.

Seemed like no big deal the first 100 times but now I"m considering adding the remote switches near the door (like a more modern coach) to eliminate the need to do so much work when I just want to hop in and go.
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Old 09-21-2006, 09:01 AM   #10
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Steven and "boatdoc",

Thanks for the follow-up. I've tested my wall switches over the past week, and it turns out that they BOTH actually work. My coach is almost always plugged into shore power, so I rarely have need of the switches. After I unplugged the coach and tested each switch with its corresponding battery/batteries, I discovered that the rewiring done by the PO had been done correctly. The only thing I haven't tested yet is the switch in the glove box that ties all three batteries together if the engine battery can't start the rig. Not quite sure how to test it, except possibly to disconnect the starting battery, press the switch, and see if the engine will start. Is that a legitimate way to do this, or will it completely disconnect everything at the switch? I definitely don't want to blow something, and have to deal with the resulting nightmare.

Best,
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Old 09-21-2006, 09:32 AM   #11
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We had a cutoff on our positive post and it broke off, it just seemed to crack. We replaced it with the same type, it broke again!! so we have given up. The first time it broke was at the border crossing in Mexicali and the second was on the freeway, we lost all power both times when we attempted to start the generator, the alternator was doing ok but could not take the genny start up load.
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Old 09-21-2006, 10:08 AM   #12
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Quote:
Originally Posted by str8strm
We had a cutoff on our positive post and it broke off, it just seemed to crack. We replaced it with the same type, it broke again!! so we have given up. The first time it broke was at the border crossing in Mexicali and the second was on the freeway, we lost all power both times when we attempted to start the generator, the alternator was doing ok but could not take the genny start up load.
Ron and Debbie,

Wow! I think I'll just leave my coach alone! Sorry to hear your troubles. I've had no trouble with my original factory setup, and I'm now going to leave well enough alone. Thanks for sharing this experience. I've been known to make trouble by trying to tinker with things that weren't broken. I never really use the switches I have, I've proven they work if I ever did need them, and I'm going to leave it at that. Just curious - what have you done now? Did you put a switch back on, or just leave it off? Do you have shore power when stored at home? I've decided my need for the shut-offs is so seldom I wouldn't put them on even if I didn't already have the factory setup. Of course, if one doesn't have access to power when stored, there is an issue.

Best,
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Old 09-21-2006, 11:14 AM   #13
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We just went back to the standard connection. We have it at a storage yard and have gotten rid of most of the power drains that we could find. With the house batteries shut off we can always use the "merge" if we need it but have not had too yet.
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Old 09-21-2006, 12:46 PM   #14
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Ron and Debbie,
If they were the post "blade style" disconnect I've heard of them breaking often. I have (from the PO) one of those big red West Marine battery cutoffs which seems to work fine. They make versions for to batteries which allow you to turn off everything from one place...but as mentioned earlier I would ultimately like to a setup more like Tim's coach where I can turn them on or off from inside the coach.

Tim,
You can easily test the battery connect by listening for a "click" when you hit the switch (this is the solenoid closing) and looking at the voltage meter on the dash...it should go up slightly.
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