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Old 04-28-2018, 03:28 PM   #1
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Relocating/replacing house battery bank

Hey all. We've got a 1997 RexAir 35' with one slide on the driver-side, and the Ford F53 chassis. We plan on dry camping a lot, so we're upgrading our battery bank and adding solar to the roof. One of the challenges is the OEM battery storage below the slide for the two group 27 house batteries just wasn't large enough for 4 T-105 GC2 batteries. We were going to move them to the storage bay just aft of the slide but the battery box was going to be just too tall to easily access the storage in the rest of that bay, so I figured I would move them to the area behind the drawers below the closet (losing those 4 drawers). This is where the converter/charge controller and the EMS-2 power management box is, along with the automatic generator/shore power relay, etc. After gutting the drawer hardware, it's big enough to easily fit 8 GC2 batteries (inside of a custom sealed box vented to the outside through the top of the refrigerator chimney to hopefully keep hydrogen away from an open flame), along with a 3000W inverter and the transfer switch that goes with that. Now my problem is that I need to relocate the house battery DC load/charge wires to that area, as well as the battery cable that I assume starts the generator. So I've got a question: the positive battery cable going from the old battery tray to the generator is only a few feet long, it looks to be 2-guage copper wire. It now has to go to the new location which is about 15 feet away from the generator. Can I still get away with using the same guage copper wire, or do I need something huge like the 4/0 wire that I've got for the main bank/inverter? We've unfortunately drained our old house batteries to the point where we needed to use the battery boost switch to start the generator from the chassis battery, so I figure that it easily started from the battery in the front of the RV, that maybe it would be fine with a longer run of the same guage. Am I wrong?

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Old 05-01-2018, 10:43 AM   #2
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Well now...this is exactly the place I was wanting to put a battery bank. On my '94 XL3300 Aerbus there is a vent pipe for the water tanks, black/gray, that goes up just in front of the aft wall of the closet. I probably over thought about that much weight on one side. Did you notice if the batteries, once in, made the rig lean to one side? I was kind of hoping to just leave the two group 27 batteries next to the gen, kind of a primary systems only thing, if needed. Maybe using one of those rotary type switches to use the on board converter or switch over to the solar bank. Wow...sorry about that...didn't realize I was rambling. I'll be watching this topic eagerly.
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Old 05-01-2018, 04:53 PM   #3
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Hey Odie! Ours also has the black/grey vent pipes in this area, and I raised the batteries 2" on a platform so that I could leave the LP gas line where it is, and also it gives me another inch by going over the very bottom of the grey tank vent pipe. I probably went overboard with the platform, I wanted to be able to slide the batteries over the front drawer-face more easily, and there's a lot of vertical space there to work on them anyway. The structure of this area is all put together with pocket-screws, so it's easy to take it apart and put it back together. Right now the plan is to stick one of the larger drawer faces back in there using spring locks like what the cabinets have on them to keep them shut, having a clear plastic face on the battery box for visual inspection, and also so that I can access the battery watering system for the bank. The rest of the drawer faces will be bolted in so it still looks original.
Another idea that I had for this was to build a battery tray to slide them into the hallway to do maintenance, but we're on the road halfway across the country from my workshop, I've only got an abbreviated set of tools and figured, I'd keep it simple for now.
We've got the ride-rite airbags on our drive axle and a tag axle, so I figured I could compensate for the weight change. Last night we were resupplying in a Wal-Mart and I completely forgot to check the level. :-( So I'm not sure how much it shifted at this point. Minus 250lbs on the driver side, plus 550lbs on the passenger side, it most likely shifted the balance. I'll have to update the thread once I find out just how much. One really good thing is that it's directly over the rear axles, so at least there's that.
Your idea of leaving the OEM batteries in place is a good one if you can spare the overall weight, that would have solved a big problem for me in starting the generator. In hind-sight, I would have done that if I still had the stock battery tray, but that was lost in a move. Now I'm thinking that I'll need to run a new 4/0 positive from the generator to the new battery bank location to start the generator, and I've got to extend the coach hookup (2 AWG) from the old location to the new, I'm more than a little worried about voltage loss for battery charging when on shore power, as well as the ability to jump the chassis battery/vice versa. I've ordered 15' of each 4/0 and 2 AWG wiring, so I guess we'll see what happens once I've got that and run some tests. The OEM coach battery wire from the bank to the battery control center in the front zigzags a bit from one side to the other, probably to go around the inline fuel filter, I think I can re-run the 2 AWG cable and save a few feet there, too.
I don't think you need to switch between the power converter/charger and solar to charge the batteries. At least for MPPT solar charge controllers, I'd expect it to compensate for the converter and only supply what's needed on top.
Now how's THAT for rambling. :-D
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Old 05-03-2018, 10:49 AM   #4
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Ahhh....okay, I see the direction now. I kind of thought about fabricating something like the auto parts stores have for their batteries, a tray long enough to hold the batteries lined up one behind the other, and locate the whole mess in a bay just in front of my rear axle. I'm playing with the idea of making a small cabinet, for the charge controller, inverter control panel and a battery monitoring system. I would like to put it in front of the refrigerator so I could run the cables through the floor. I'm still in the want to stage, unfortunately ye ol job keeps me limited on time I get to spend on my little rig.
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Old 05-07-2018, 01:49 AM   #5
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Over the weekend I did some wiring, I separated the battery connection from the harness up to where it crossed over from the driver side to the passenger side, now it easily reaches the smaller storage bay just aft of the entry steps. I bolted it to a remote battery post inside that bay. I then ran 6' of 4/0 cable from that post to the new battery location under the closet, and ran another 14' length of 4/0 cable from that post to the generator start cable and spliced them together. Now I show 13.7V at the converter, and also at the generator and battery bay, looks like no voltage loss.
The 4/0 generator start cable might be overkill, but I can't find how many amps the generator starter draws anywhere. I did find someone with my generator who didn't have adequate wiring and it caused the starter gear to fail, so I wanted to make sure it could handle it.
Batteries are all wired up and charging. Tomorrow I'll try to fire up the generator. Gee...I hope it starts...
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Old 05-07-2018, 01:18 PM   #6
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Fingers crossed...I get excited when a plan works out like it ,well was planned.....you get the idea
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Old 05-07-2018, 06:07 PM   #7
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Did the generator test a bit ago, fired right up. As a bonus, the current sensor for the air conditioner management box (under the closet where I've been spending so much time...), was unplugged from the box. I plugged it back in and now the system offloads the air conditioner when we run the microwave, and when the generator is on we can run both front and back units at the same time which we've never been able to do before.

I love it when a thing comes together.
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Old 05-29-2018, 04:44 PM   #8
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Mostly done

Wanted to post a follow-up now that it's all together and working. I've got the 4x200w panels in a row on the driver's side. We put them here to try and even out the added weight from the battery bank being relocated to the passenger side.

I wired them up in 2 sets of two in series and ran the 10 feet of 10 AWG solar extensions down the refrigerator vent, then through the factory wire conduit into the closet where we put a combiner and fuses. Then 4 AWG wire from there to the charge controller (8'), another foot of 4 AWG wire from the charge controller to the distribution blocks. The inverter and transfer switch are also located here along with a small relay to switch off the converter when not on shore power.

Then I built a simple battery box vented to the top of the refrigerator vent.

I mounted the shunt and battery fuse to the outside of that.

I put a battery watering system on the 8 GC2 batteries so that I can water them from a single point behind the old drawer faces.
We just got back from boondocking on some BLM land over the holiday weekend and everything worked great, we even got up to 800W yield a few times over the day. We got about 3-4kwh per day on a sunny day with no tree cover.
We found that our stored battery power is a lot like money. It's a LOT easier to spend it than it is to get it back! But doable. :-)
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Old 05-30-2018, 09:44 AM   #9
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Oh wow...that looks great. I'm so jealous. That is a good bit of power
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Old 06-13-2018, 05:00 PM   #10
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Using 3M 5200 for solar install

I forgot to mention that we used 3M Fast Cure 5200 marine sealant to fix the solar panels to the roof. When I did this, it was about 70F with 60% humidity. The temp and especially humidity are important with this adhesive/sealant.
When we first got the RV we coated the roof with Dicor Fiberglass Roof Coating, and we primed it using the Dicor roof prep first. The bond that the coating has on the fiberglass roof seems extremely strong, and the bond that the 5200 has with the roof coating is probably even stronger. If there is ever a failure, I would expect it to be with the Dicor coating and the fiberglass roof itself. The steel gridwork that reinforces the roof is spaced every 24", I did try to put the panel mounts over these wherever possible, only missing the one right in front because it's under the front cap seal which goes at a slight angle and isn't flat. I'm inspecting it each time before and after we move from place to place, and so far it's holding up fine. I figure if I ever see a problem (hopefully I don't HEAR a problem while in route), then I'll bolt them down.
If anyone else has used 5200 to mount equipment to their roofs, I'd love to hear from you. Thanks.

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