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Old 05-15-2006, 05:01 PM   #1
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1992 21' Sovereign
Oakland , California
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Need an Electrical Guru

I'm adding a second battery box to my 1992 21' Sovereign. I purchased the hardware from a salvage yard and last weekend I successfully made the scary cut on the outside skin in order to mount the box. I'm pretty good with mechanical things but electrical stuff baffles me. I've communicated with another forum member who did this to an older rig - both of his batteries connect at the kill switch. I looked at my father-in-law's 1987 25' Sovereign and his connect at the kill switch, too. However, in my rig, the breakaway switch and charge line enter the system through thermal breakers prior to the battery connection at the kill switch. This is probably elementary to you electricians out there, but, frankly, I'm not sure where to introduce the 2nd battery into the system. Here is a diagram of my current wiring:

Here's what it actually looks like:

Here is a wiring diagram of a 2-battery setup:

I have a new 50 amp thermal breaker for the second battery. My question - do I connect my second battery at the 50 amp breaker post of the first battery? Do I connect it to the kill switch? Do I move the breakaway and charging line to the kill switch, too?

I appreciate any insight you can provide.

Thanks,

-Mark
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Old 05-15-2006, 05:06 PM   #2
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ok, I'm not sure how I screwed this up - here are the images.

Single battery wiring diagram:

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Name:	1992 Airstream <a title=Sovereign - 1 battery wiring diagram.jpg Views: 171 Size: 25.5 KB ID: 21325" style="margin: 2px" />

What it actually looks like:

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Name:	Current Wiring.jpg
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Size:	55.3 KB
ID:	21326

Two battery wiring diagram:

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Name:	1992 Airstream Sovereign - 2 battery wiring diagram.jpg
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Old 05-15-2006, 05:08 PM   #3
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I don't know that answers to your questions but I would like to suggest to put heat shrink on the meat collars of those lugs that have them exposed. Cuts down on corrosion and less exposed conductor. Good looking work, BTW.
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Old 05-15-2006, 05:28 PM   #4
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Not too sure of your layout, but if the batteries are close together and both are the same rating and similar age, and are 12volt, connect the two positives together and the two negatives either together at the post or, if the chassis grounding/earth, what ever its called there, is very reliable then connect to negatives to that. If the batteries are a bit apart from each other fit a fuse between them. Rate the fuse for the maximum output of the battery to the services.

Then fit a fuse to the services i.e., if you are pushing 3000watt inverter use a 250-amp SLOW BURN fuse (divide watts by volts). A slow burn fuse will take care of initial start surge.

If the batteries are of a different rating or age then be careful.. The weaker one will drain the better.

If you use 2 x 6volt for a higher amp/hr rating (say 2 x 225 amp/hr at 6volts) then connect the negative of one battery to the grounding. The positive of that battery connect to the negative of the second one and use that one’s positive for the supply as above.

In all cases use the heaviest duty cable you can get 25 or 35mm; minimum. The heavier the better, for minimal voltage drop.

Hope this helps.
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Old 05-15-2006, 11:04 PM   #5
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Factory Wiring

Quote:
Originally Posted by AYRSTRM2
I don't know that answers to your questions but I would like to suggest to put heat shrink on the meat collars of those lugs that have them exposed. Cuts down on corrosion and less exposed conductor. Good looking work, BTW.
John,

Thanks, but I can't take credit for what you see in that picture - that's the factory stuff. I posted the picture to see if someone can give me some guidance on where, exactly, to connect the second battery.

I would appreciate any feedback.

Thanks,

-Mark
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Old 05-16-2006, 01:17 AM   #6
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"Piggy back" them....!?

Mookie -

I would 'piggy back' on what "Chuckles" suggested. If the batteries are to be mounted side by side, then do what the factory did with my side-by-side dual battery set up and....

Hook the Coach Positive to one battery. Hook the positive and negative on both batteries together. Then hook the Coach Neg to the second battery. Done.

That's how mine came from the factory and it works AOK!

My .02 cents - .01 cent borrowed from Chuckles!

All the best!

Axel
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Old 05-16-2006, 08:25 AM   #7
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Quote:
Originally Posted by AYRSTRM2
I don't know that answers to your questions but I would like to suggest to put heat shrink on the meat collars of those lugs that have them exposed. Cuts down on corrosion and less exposed conductor. Good looking work, BTW.
What John said! I have found that a lot of operational problems relating to 12VDC start with internally corroded battery terminals. Use the heat shrink tubing (it also comes in strips or you can slit the tubing if you don't want to disconnect the cables) and be sure to cover the exposed end of the cable and overlap the cable insulation too. Not a bad idea to clean the connections while you are at it and put some terminal sealer (NAPA) on them at the same time.
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Old 05-16-2006, 11:04 AM   #8
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More Questions

Thanks to everyone for the feedback.

Again, I have to say that these electrical challenges baffle me, so I have some additional questions. If I connect the positive from the second battery to the lug of the kill switch where my first battery is currently connected (location 1 in the photo below), is that the same as connecting the two positive battery posts together? Do I need to be concerned that the breakaway switch and charge line (location 2 in the photo below) are connected to the 50 amp thermal fuse from the first battery prior to the first battery connection to the kill switch?

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Thanks,

-Mark
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Old 05-16-2006, 11:53 AM   #9
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your battery should not be connected right to the kill switch, this would mean that your 50a thermal overload is NOT in the circuit. your system is rated for 50amps if the battery puts more than that out or a surge back to the battery (charging ) it will open (blow, pop) it appears that adding a second battery ,they put each battery w/ there own 50amp thermal protection (from schematic) that is a good idea and i would do it that way, but not necesssary, it does make it easier to trouble shhoot.. i would follow chuckles advice as it is sound. remember you want both batteries in parallel to keep it 12v. i.e. + to + and - to - like jump starting a car, same potential.
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Old 05-19-2006, 10:09 AM   #10
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vaseline is also a cheap and easy way to coat battery connections for anti-corrosive protection! that's a tip from my dad and have used many years till this day on all my autos.

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Old 05-19-2006, 11:27 AM   #11
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Quote:
Originally Posted by Mookie
Thanks to everyone for the feedback.

Again, I have to say that these electrical challenges baffle me, so I have some additional questions. If I connect the positive from the second battery to the lug of the kill switch where my first battery is currently connected (location 1 in the photo below), is that the same as connecting the two positive battery posts together? Do I need to be concerned that the breakaway switch and charge line (location 2 in the photo below) are connected to the 50 amp thermal fuse from the first battery prior to the first battery connection to the kill switch?

Attachment 21336

Thanks,




-Mark
If you have a thermal breaker installed in the line from the battery to the kill switch, it would be OK to connect the line from the second battery to the kill switch as you describe. If it were mine, I would connect the second battery to the thermal breaker at the same place as battery one. Then one breaker will protect the entire system. Connecting both batteries together at the batteries will accomplish the same thing. What ever way you do it, there is no problem with the breakaway switch connected as shown.

Jim Mickle
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Old 05-22-2006, 06:39 PM   #12
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Quote:
Originally Posted by crowbar68
vaseline is also a cheap and easy way to coat battery connections for anti-corrosive protection! that's a tip from my dad and have used many years till this day on all my autos.

crowbar
Also great to stop bleeding in an open wound !
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Old 05-22-2006, 09:30 PM   #13
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Thanks to everyone for the input.

I installed the second battery box last weekend and I did use a 50 amp thermal breaker on the second battery. I then connected the second battery to the lug which connects the breakaway switch, the charge line and the first battery (location 2 in the photo above).

I'm glad I spent a lot of time making a template and rechecking my measurements before making the cut in the outside skin. These battery boxes leave very little (@ 1/8 inch) margin for error. The finished product looks just like a factory installation. I finished the job right at sundown so I didn't get the chance to take pictures. I'll take some in the next couple of days and post them here.

Thanks again for the help. I love this forum.

-Mark
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Old 05-31-2006, 08:45 PM   #14
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Almost Done

Here are some pics of the (almost) finished project.

Here is the inside showing the new box, 50 amp thermal fuse and final hookup (sorry about the fuzzy picture):
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Name:	Second Battery Hookup.jpg
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This is what our new (used) second battery box looks like from the outside:
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Name:	Second Battery Installation.jpg
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-Mark
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