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Old 08-09-2018, 02:56 PM   #1
Join Date: Aug 2018
Posts: 20
Year: 1955
Coachwork: Chevy
Chassis: 6700
Engine: 327
Charge controller and electrical system review

My bus is currently set up for just boondocking, sort of. There is a spot for two batteries and wiring to the water pump and house lights. The roof A/C, 2-way fridge, and Oven light have A/C cords. Iíd like to add a charger and a hook up for shore power for now and a generator at some point. Solar would be cool too. Iím thinking about a 35 Amp convertor/charge/distribution panel, would that be enough? The roof air is 20A. Add fridge, water pump and lights and itís 33 Amps. Iím not sure what the draw to charge the battery or how the lights and water pump factor in. I suppose they will run off the battery until it gets low enough to trigger the charger. With 20A to the airconditioner, the 35 Amp power panel will have 15 Amps left for everything else. I plan on having one or two batteries, what is the typical demand for charging? The description for this power panel isnít clear about what it can do, WFCO brand.
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Old 08-10-2018, 06:07 AM   #2
Bus Nut
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Join Date: Feb 2017
Location: The West
Posts: 757
Year: 1998
Coachwork: MCI
Chassis: 102 EL3
Engine: DD 60
Rated Cap: 50k
Get a Kill-a-Watt meter from Amazon and measure your power consumption. Perform an energy audit (or budget) and you will know how much power you need each day. No need to guess.
JD - Full timer out west
Missy - 1998 MCI 102-EL3 - 1.7kW Solar - 10kWh Lithium
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Old 08-10-2018, 05:25 PM   #3
Join Date: Aug 2018
Posts: 20
Year: 1955
Coachwork: Chevy
Chassis: 6700
Engine: 327
Thanks for the reply, but Iím not sure how to apply that to this situation. Basically I am building the power system from scratch. Based on the specs for the air conditioner DuoTherm: Model 57915.331 20Amps 3.5KW gen.
Iím considering the Sportsman 4000 propane generator 4000 surge watts/3250 running watts.
I read on Batterystuff website ďIt will depend on the efficiency rating of the charger/converter power-supply you intend to use. Once you find a brand that you intend to use look to their AC Input ratings. The AC voltage x AC Amperage = The Wattage. The Wattage rating has to be below your continuous run rating of your generator.Ē
So with that 3250W/120V = 27.08 A so an power panel rated about 25 A?
Taking into account the rest of the appliances, the fridge Dometic Model RM 36a 1Amp,
Water pump may be 4A, Lights total may be 8.5A. I donít have a kill a watt, but Iíll check the A/C with a current clamp, and Iíll have to borrow a car battery to check the dc draw of the pump and lights with a DMM.
Iíd like to get the power panel first and get the batteries later, am I limited to a 25A panel if I intend to get the 3250 W generator?
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Old 08-10-2018, 10:15 PM   #4
Bus Crazy
Join Date: Jun 2013
Location: Picton,Ont, Can.
Posts: 1,017
Year: 1997
Coachwork: Bluebird
Chassis: GMC
Engine: Cat 3116
Rated Cap: 72
So any place you may stop and go on shore power, you need a minimum 30 amp setup. So that's where your build starts.
Offered will be 30 amp and 50amp services in an rv setting or anywhere you stay in North America.
So pick one. Build to that standard or greater for the difference in cost.
Always oversize not undersize with electrical components no matter what they are, switches, panels, chargers, appliances etc.
Sounds like you should build it for 50 amp service and a panel with as many circuits as you can find, both dc and ac circuits.

Install it where you want it and wire whatever it is you need. One piece at a time gets it done.

Question everything!
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Old 08-13-2018, 11:23 AM   #5
Join Date: Aug 2018
Posts: 20
Year: 1955
Coachwork: Chevy
Chassis: 6700
Engine: 327
Yikes! Iíll avoid the 50A setup. Iím still trying to wrap my head around the math to determine how everything works together before purchasing costly components. I currently have the roof air connected to my house via a 100í 10-gauge 20A extension cord connected to a 20A breaker. The roof air draws 10 to 20Amp according to the current clamp. I realize this is less than optimal, but it works.
The generator Iím considering can supply 3250W/120V = 27.08A continuous and 4000W/120V = 33.3A surge. The roof air draws 20A. Fridge 1A, Stove and oven have a light 1A, and thatís all for the A/C side for now anyway. Thatís 22A.
I went to Camping World to look at power panels, but they had none on the shelf. I thought I could get the Input rating off the box since I couldnít find it on the manufacturers website. If I look at the description of the WF-8735 model converters provide 35 Amp DC output, and a highly reliable nominal 13.6 VDC with or without a battery. So, 35A x 13.6 vdc = 476 W. From that I figure 476W/120vAC = 3.97A this doesnít include the efficiency or losses of the convertor so I could say 5A A/C going into the power panel yields 35A dc output.
The dc appliances include Water pump 6A, Three 1141 bulbs in the kitchen, bathroom, and step rated at 18.4W/12.8v = 1.44A x 3 = 4.3A . Two Edison Screw bulbs in the dining area, and bedroom I found an led version rated at 4.5W/12.8v = .35A x 2 = .7A. A toal of 5A for the lighting. The stereo may be 1A. so 12A dc total, thatís less than half what the power panel is rated for.
22A plus 5A convertor = 27A, should be doable with that generator or 30A shore power. This at least gives me a baseline to work from, that is if Iím on the right track. Does anyone see anything off in this math? This system leave little wiggle room, but is not too far off. Still unknown is battery charge.
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