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Old 02-06-2018, 04:00 PM   #1
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Upgrading wire from converter - where to connect it?

Short question: should I connect my new wire from the converter to the battery cutoff switch, or should I connect it directly to the battery control center?

Longer version:
I'm upgrading the wiring between my converter and my batteries. In my 2013 Sunseeker 3170 DS these connections are through 6 gauge wire. The positive goes from the converter to the fuse panel under the bed to the battery cutoff switch, to the battery control center box ("BCC"), to the batteries. (see this old post if you like awesome diagrams: Converter Wiring Thanks Snowman9000!)

I'm replacing that wire run with a new 2 gauge wire. I can't run it through the fuse panel under the bed like the OEM wire because that panel can't handle anything bigger than the existing 6 gauge wire. Consequently, I'm running it directly from the converter to the stepwell area where the battery cutoff switch and the battery control center are.

I can replicate the functionality of the OEM system by connecting my new wire to the battery cutoff switch and leaving the 6 gauge wire that feeds back to the fuse panel. It's a little more hassle to get the wire to the switch - have to feed it back inside the coach to get there and then run a new 2 gauge wire from the switch to the battery controller - but not a big deal.

I've read a few times on the forums that newer Sunseekers and Foresters changed the way the converter was wired. The change is described as allowing the converter to charge the batteries even when the cutoff switch is in the off position. This leads me to believe that in newer motorhomes, the converter is wired directly to the battery control center, which then feeds power from the converter directly to the batteries and power to the 12 volt loads in the coach back through the cutoff switch to the fuse panel.

From a functional standpoint, in my existing system, if the battery cutoff switch is turned off and the converter is attached to shore power, most 12 volt loads (interior lights, TV's, propane/CO monitor etc.) will operate but the batteries will not charge. If I connect my new wire directly to the BCC, the battery cutoff switch will turn off the 12 volt loads when attached to shore power, but allow battery charging.

My question is this: Should I replicate the existing system by running my new wire to the cutoff switch, or should I emulate how (I think) newer models of my rig are wired and run the wire directly to the BCC? From a functional standpoint, while on shore power do I want the battery cutoff switch to control charging of the battery or do I want the switch to control 12 volt loads?

Right now, I think I'm more likely to want to charge the battery and turn off the interior 12V loads. Someone please talk me out of attaching my new wire directly to the BCC if that's a bad idea.
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Old 02-06-2018, 08:41 PM   #2
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Old 02-06-2018, 09:51 PM   #3
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My converter is connected directly to my battery bus and is always on and can't be disconnected. Instead of running expensive 2 gauge wire for a long distance, consider mounting your converter next to your batteries. It was easier for me to run romex under the camper to my relocated camper. My batteries reach 90% state of charge almost 50% quicker because I'm no longer losing almost .5 volts from the long run of thin factory wire.

As a general rule of thumb, you should not rely entirely on your converter for 12 volt interior power. The use of a slide or electric jack or stabilizer jacks introduces a high start up load that your converter may not be able to supply and may damage it. A battery provides the necessary buffer for these high startup loads.

Most new campers today have led lights and interior 12 volt loads are not much of an issue and should not impact the time it takes to recharge your battery. I find that my batteries never are able to accept a charge rate equal to the full capacity of my converter when I go down to 50% depth of discharge.
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Old 02-06-2018, 10:26 PM   #4
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Quote:
Originally Posted by Skyliner View Post
My converter is connected directly to my battery bus and is always on and can't be disconnected. Instead of running expensive 2 gauge wire for a long distance, consider mounting your converter next to your batteries. It was easier for me to run romex under the camper to my relocated camper. My batteries reach 90% state of charge almost 50% quicker because I'm no longer losing almost .5 volts from the long run of thin factory wire.
I considered this and agree that moving the converter closer to the batteries is a better solution. The places I could find that were closer to the battery were pretty small and I was worried that there wasn't enough ventilation to dissipate the heat the converter generated. In the end, I decided to leave the converter where it was and use the biggest wire that would fit in the lugs.

Quote:
Originally Posted by Skyliner View Post
As a general rule of thumb, you should not rely entirely on your converter for 12 volt interior power. The use of a slide or electric jack or stabilizer jacks introduces a high start up load that your converter may not be able to supply and may damage it. A battery provides the necessary buffer for these high startup loads.
Interesting. I hadn't thought about that. The slides in mine are powered from the BCC (instead of the fuse box) and the stabilizer jacks are connected directly to the batteries, so in the OEM setup with the skinny wire, turning off the battery switch disconnects the big loads from the converter but leaves them attached to the battery. If I connect my wire directly to the BCC, the slides and jacks will always be connected to both the batteries and the converter. So either way, those high-draw loads are always connected to the battery. That probably doesn't change how I wire it, but it's worth thinking about.

Quote:
Originally Posted by Skyliner View Post
Most new campers today have led lights and interior 12 volt loads are not much of an issue and should not impact the time it takes to recharge your battery. I find that my batteries never are able to accept a charge rate equal to the full capacity of my converter when I go down to 50% depth of discharge.
Another good point. Disconnecting the interior 12V loads won't contribute much to faster charging. My thinking for wanting to disconnect the 12V loads while allowing charging was more related to storage and leaving the converter powered to keep the batteries topped off.

Thanks for your input Skyliner.
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Old 02-10-2018, 02:01 PM   #5
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I considered this and agree that moving the converter closer to the batteries is a better solution. The places I could find that were closer to the battery were pretty small and I was worried that there wasn't enough ventilation to dissipate the heat the converter generated. In the end, I decided to leave the converter where it was and use the biggest wire that would fit in the lugs.


A great plan and one I'm in the midst of myself. On my distribution panel I can use a 1/0 wire max. On my TT the converter is close enough to the batteries I can get away with #4 AWG which is more than enough to handle everything I could possibly want to run, including my inverter that just runs my TV and any 120V tool battery chargers I might need to use. (the Inverter is a TSW, caution----most tool battery chargers don't play well with MSW).

The new Converter which is scheduled to arrive Monday can also handle up to 1/0 wire.

Rather than confine the converter to the small compartment in the WFCO enclosure I'm just moving it into a large empty space under the refrigerator. Infinitely more cooling area than under the distribution panel.

Only suggestion I have is that people don't move converters close to a sleeping area. I rented a Class C many years ago that had the converter and fuse panel in the rear bedroom. Whenever the furnace kicked on, so did the cooling fan in the converter. It was noisier than the furnace
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