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Old 09-18-2014, 08:38 AM   #1
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Join Date: Sep 2014
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Coach Battery Modification Majestic 28a

We have a new to us 2008 Four Winds Majestic 28a. I want to modify the coach battery storage to a sliding tray capable of holding up to 4 6v batteries. The current tray holds one 12v class 31 battery lengthwise across the MH beam. I have measured and there is up to 28" in width, 17" depth, and more than adequate height. Has anyone done a similar mod to this specific MH? Which sliding tray will fit and support the weight? How did you attach the new fabricated support system that holds the sliding tray? Where did you install the inverter? Should I post this somewhere else in the forum? Thanks for the help!

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Old 09-19-2014, 08:56 PM   #2
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Join Date: May 2014
Location: flint river, flat shoals area
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just got your post and question. we have two rv's for two different purposes. one 22' rv is for traveling to someone's house at the destination. in that one, a type 29 battery does fine in the cold temperatures overnight (running the heater fan and lites) and the daytime driving does the charging. The other 23' rv is for camping weekends or longer. It uses two type 31 batteries and can handle two full days of dry camping (inverter and heater fan). Both rv's have been east coast - west coast and both battery setups did fine. Considering a type 31 weighs in at about 70lbs, you might consider locating a battery tray from an older larger rig for your installation. My point: do you really need that much weight to fulfill your capacity requirements? check on the type 29 battery (lighter) with a 210 RC rating - it would give you 210 minutes of 25 continuous amps, or about 400 minutes of intermittent amps ( - that's all night running your heater fans and making coffee for you in the morning!). Let us know ! Tom and Rho

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Old 09-22-2014, 02:59 PM   #3
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Location: Indiana
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I have a 2008 Four Winds 5000 (28A floor plan), which should be exactly the same layout as yours.

The thing that governed my battery mod choices was the fact that I wanted the tray to slide out of the existing battery access door in the side of the RV. I did not want to cut a new opening into the fiberglass side of the unit and frame in a new access door. This meant that the batteries had to slide out "single file" in a line, and four batteries were out of the question. Even with this arrangement, things got pretty tight fitting the batteries to slide out the door and still clear the end of the propane tank. If I had gone with wider batteries I would have had to move the propane tank rearward a couple of inches.

My choices were two 6 volt batteries in series, or three 12 volt batteries in parallel if I wanted more reserve. The 12v ones would have required trimming the door opening a little and shifting the propane tank back, so I went with two 6 volt GC2 size golf cart batteries from Sam's Club. Together, they provide 232 Ah and are rated for 122 minutes @ 75 amp draw. This is more than enough for my power needs and have lasted through 3 nights with limited inverter use for watching TV at night and making coffee and toast in the morning.

If you put in 3 GC12 size batteries, the cost doubles, but you get 450 Ah and a reserve of 225 minutes at 75 amps. Four GC2 6 volt batteries will be a lot more hassle to install, and the reserve gain is minimal.

If you go with the 12 volt batteries, I would still recommend the golf cart battery and not the marine/rv deep cycle starting batteries. The latter is a compromise between a true deep cycle battery and an automotive starting battery. You are never going to use these to start anything, so why not use batteries optimized for deep cycling at lower discharge rates?

As far as the slides are concerned, I bought some heavy duty 200lb storage tray slides and fabricated the tray table and cage to hang it from myself out of 2 inch and 1.5 inch angle stock. I hung then from the same four bolts that the original battery cage was hung from. Those are 3/8 bolts that go all the way through the floor and have 2" diameter flat heads that sit under the carpet. I feel very confident in them to hold my 120 lbs of batteries.

I put the inverter under the front dinette seat where most of the electrical stuff already was. It made it easy to wire in the 120v part of the install, and kept the 2/0 gauge 12v cable to the batteries pretty short. I put a cut-out in the seat wall behind the drivers seat and installed a 120mm computer case fan to insure there was enough ventilation under the seat for the inverter. I have checked after running the inverter for a couple of hours, and it stays fairly cool in there.
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Old 09-23-2014, 06:21 AM   #4
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Thanks for the responses! We are planning to full time after my retirement. We plan to boondock for one or two weeks at a time. Our first host job next summer has no electricity. We have 400W of solar panels with a 40 amp MPPT controller. I was thinking the door for our generator is the right length to put in up to four batteries. Cutting the lower skirt to fit the new door and building a new support cage is a lot of work, but I'm willing. I'd probably use two sets of 200# sliders to hold the weight. Start with 2 6V GC batteries with the option to add two more. Don't like the weight, but like the off-grid power options.
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Old 09-23-2014, 10:03 AM   #5
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Location: Indiana
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If you are boondocking for that length of time, you will probably need more battery capacity than I do. I very rarely go more than a night or two before I can run the generator for an hour to recharge the batteries, or I am on the road and the alternator does it for me. I thought about adding some solar panels, but I am mostly in wooded camping areas, so the shading makes them not worth the money for me.

Unfortunately, you will have to fabricate a cage and hanger system no matter what you do, because the one that comes with the unit will never hold more than one battery. You can either buy a battery slide tray already put together and just make the hanger system yourself, or get slides and make the whole thing yourself like I did. Kwikee is the big manufacturer of pre-made battery trays and they come in about a dozen sizes. If you just want cargo slides, Delcity has a nice selection of them online.

Have fun in the boondocks! I have another seven or eight years before I have to think about what to do in retirement
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battery, cat

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