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Old 11-28-2017, 09:51 AM   #1
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Installing a battery disconnect.

I always learn something here, so feel free to opine.
I'm installing a battery disconnect.
Of course, it's not as simple as taking the one positive or the one negative through a switch. There are several cables, and a mix of post and ring terminal.
But not all of them have a draw.
This picture is not my battery box, but it's very similar (Mine is in the storage place, 25 miles away, so I want to think this through)
The small black wire at the top (I think goes to the jack)
No draw.
The jumper between batteries can be left in place, no draw.
The two larger black cables in the lower left are returns from the converter? Yes/no?
Obviously, the large covered post is the main feed.
I recall there's also a small pair to the Zamp plug for the solar charger (which I don't have.) no draw.

It doesn't really matter which + terminal wires are attached to since the batteries are paralleled.

Can I get it down to one wire going to the switch? And one return? (The covered red main feed?) How hard is it to cut off the post and add a ring terminal?

Bonus question: Should I put a rubber mat under the batteries to slow corrosion?
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Old 11-28-2017, 10:06 AM   #2
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Hi

One big fat cable goes to the inverter. The other big fat cable goes to the converter and the rest of the loads in the trailer. The jack has no draw *unless* you happen to leave the light turned on ... don't ask how I know about this

You only need to "switch off" the positive side or the negative side. No need to disconnect both of them. There's a lot of debate about which side to switch. Once you get it installed both ways work fine. With proper care, you can install the switch on either side. One short / fat wire to the switch should be fine. One long / fatter wire to the switch also will work if it's mounted inside the trailer.

Rubber mats are a good idea. They may not "vent" well. That will trap moisture under them. Finding one that holds up the weight of a battery and still drains .... not so easy. Even if it does not drain, it will protect against grit on the bottom of the battery. We *all* scrub the bottom of the battery while lifting it into the trailer don't we ... why does my arm ache so much

One really good reason to leave the Zamp connector on the battery vs on the switch: That's where the trickle charger plugs in ....

One other note: There is a tradeoff between smearing everything with grease to corrosion protect it and bolts remaining tight. Apparently the last guy to play with my batteries didn't quite get it right. Truth in lending - yes this is something I should have checked earlier

Bob
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Old 11-28-2017, 10:13 AM   #3
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Informative thread from this summer that includes what a couple different guys did. it's on my to do list. http://www.airforums.com/forums/f542...ll-168120.html
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Old 11-28-2017, 12:06 PM   #4
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Quote:
Originally Posted by uncle_bob View Post
One big fat cable goes to the inverter. The other big fat cable goes to the converter and the rest of the loads in the trailer.
Lots of information here.

If I have not turned the inverter on can I leave it connected without running the batteries down?
Quote:
No need to disconnect both of them.
Obviously.
Quote:
There's a lot of debate about which side to switch.
I think either works fine. I understand IF you're using a disconnect with a knife switch or one with a lot of exposed metal, to do the negative side, as accidental shorting is greatly reduced. Electrically, it doesn't matter.
Quote:
One really good reason to leave the Zamp connector on the battery vs on the switch: That's where the trickle charger plugs in ....
Yeah, my trickle charger is a NoCo Genius which has a proprietary connector, so I'll just leave it in the battery box. (I didn't mention that here.) Still, the Zamp connector is handy in case I decide to put some 12 v. do-dad outside the trailer.
Quote:
One other note: There is a tradeoff between smearing everything with grease to corrosion protect it and bolts remaining tight.
I use the spray that makes everything red but stops corrosion.

BTW. With two batteries, before I disconnect everything, I call them battery one and two. All wires going to the positive side of battery one gets one red cable tie, the positive side of battery two gets two red cable ties, etc. Then take a picture of it.
I'm less likely to overlook something (Like when the generator in my MH refused to start. Oops!)
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Old 11-28-2017, 12:50 PM   #5
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Quote:
Originally Posted by pcskier View Post
Informative thread from this summer that includes what a couple different guys did. it's on my to do list. http://www.airforums.com/forums/f542...ll-168120.html
Supurb. Thanks.
I like the disconnect with the SPDT switch. Batt. 12v. in; Converter and Inverter out. (sort of inverted thinking from the boating world where the switch chooses battery one or battery two or both.)
I don't understand why people worry about balancing the load across two batteries when they're tied together with 4 ga. jumpers?
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Old 11-28-2017, 12:56 PM   #6
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I'll save you some trouble. Here are 2 reference wiring diagrams I've created for a battery disconnect for standard airstream travel trailer.

There are 2 different switches that could be used, which is why I have provided 2 diagrams.

Link above will provide more color / background.

Enjoy.
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Old 11-28-2017, 05:49 PM   #7
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Quote:
Originally Posted by wulfraat View Post
I'll save you some trouble. Here are 2 reference wiring diagrams I've created for a battery disconnect for standard airstream travel trailer.

There are 2 different switches that could be used, which is why I have provided 2 diagrams.

Link above will provide more color / background.

Enjoy.
Yes, I saw those on the other thread and downloaded them. I think I like the top one as it just seems more elegant a solution, one cable per post. I guess if you don't use the inverter you could just select "battery 1".

I considered the DPDT marine switch also, but I didn't see any real benefit. (two in; two out)

I've been reading up on making your own battery cables or replacing the post terminal with a ring terminal.
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Old 11-28-2017, 06:16 PM   #8
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I agree that #1 is more elegant - that is how I wired my last 25'. It allows you to turn on/off the trailer, turn on/off the inverter, or both.

When I had that switch in my last trailer, I would typically select portion "1" - trailer only, to avoid unnecessary phantom draw from the inverter (the inverter will draw a standby (low) current even when the inverter itself is turn "off" using the wall switch inside the trailer.)

Blue Sea M switches are the way to go. Designed for outdoor use and fit in the battery box. Blue Sea partner number 6007 is the one you want for option 1. Cost is ~ $30.

https://www.amazon.com/Blue-Sea-Syst...=blue+sea+6007
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Old 11-29-2017, 07:05 AM   #9
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Quote:
Originally Posted by Mollysdad View Post
Lots of information here.

If I have not turned the inverter on can I leave it connected without running the batteries down?

Obviously.
I think either works fine. I understand IF you're using a disconnect with a knife switch or one with a lot of exposed metal, to do the negative side, as accidental shorting is greatly reduced. Electrically, it doesn't matter.
Yeah, my trickle charger is a NoCo Genius which has a proprietary connector, so I'll just leave it in the battery box. (I didn't mention that here.) Still, the Zamp connector is handy in case I decide to put some 12 v. do-dad outside the trailer.
I use the spray that makes everything red but stops corrosion.

BTW. With two batteries, before I disconnect everything, I call them battery one and two. All wires going to the positive side of battery one gets one red cable tie, the positive side of battery two gets two red cable ties, etc. Then take a picture of it.
I'm less likely to overlook something (Like when the generator in my MH refused to start. Oops!)
Hi

The inverter is normally the biggest parasitic load in the trailer. It, more than anything else is the one thing you want to have the disconnect switch "shut off" If you are going to put the switch in only one wire, put it in the inverter wire.

Bob
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Old 11-29-2017, 10:20 AM   #10
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"One really good reason to leave the Zamp connector on the battery vs on the switch: That's where the trickle charger plugs in ...."

My Battery Tender Plus plugged into the Zamp socket, but the Zamp cable was incorrect polarity, as wired by Airstream. It's red lead went to Positive. Did you flip the leads to plug in your trickle charger?
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Old 11-29-2017, 10:57 AM   #11
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Not as elegant as the Blue Sea marine switches but this kind of a disconnect can be installed within your battery box in under half an hour. You then just work out which line goes to your external trickle charger plug and put it on the side closest to the battery and everything else on the downstream side of the switch. Or, you can just clip the trickle charger onto the battery terminals with the alligator clips that come with it.
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Old 11-29-2017, 12:30 PM   #12
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Quote:
Originally Posted by james.mileur View Post
"One really good reason to leave the Zamp connector on the battery vs on the switch: That's where the trickle charger plugs in ...."

My Battery Tender Plus plugged into the Zamp socket, but the Zamp cable was incorrect polarity, as wired by Airstream. It's red lead went to Positive. Did you flip the leads to plug in your trickle charger?
Hi

I made an adapter ... Then the storage place let me know they had a space indoors available (we've been on a waiting list ) ..... with no power ... The batteries are now sitting in the garage. Not sure what we'll do if we don't get a space with power by next spring.

Bob
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