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Old 01-14-2016, 12:49 PM   #1
rossfree's Avatar
Join Date: Jan 2016
Location: Fairfield Bay, Arkansas
Posts: 140
Year: 1990
Coachwork: Chevy
Chassis: Ward?
Engine: 8.2 liter ?
Rated Cap: 24 Passenger
Simpler Electrics... Newbie to Skoolie :-)

Hi all,

Second post... I just purchased a 1990 Chevy Ward 24 passenger Skoolie. Pics uploaded. Seats are out and work is underway to remove side panels... I'm hating rivets right now.

Anyway, somewhere, in all the googling I've done, I ran across someone posting that they installed a 120VAC / 20amp reel-type extension cord. One of the retractable cords you hang in your garage. I own one... love it!

Rather than connect up with a 30amp or 50amp extension cord, they used the retractable cord / 12volt charger to keep the batteries charged up. All 120VAC in their bus was through their inverter(s).

I can't find the original post and do not know how to begin to search for similar information so excuse me if this is a redundant thread.

I like the idea. Simple... no transfer switching, nice, 30ft retractable cord. Single or multiple inverters that can be turned off when not needed so as to hold down phantom loss.

In my bus, I plan to have the following: Small 5000 BTU Wally World window AC.
6 cu ft Home Depot upright freezer - with secondary temperature control to use as a refrigerator. A drop in single burner induction cooktop. Small convection toaster oven. Small Wally World microwave oven. Led lighting. 12volt ceiling vent. Charging ports for computer / iPad / cell phones. I currently plan to have two 125 amp/hr 12volt marine batteries in parallel.

I am aware of inverter losses. Is it practical to run off of the battery/inverter(s) with just a 120vac / 20amp extension / battery charger configuration? Of particular concern is running the AC. If the AC is running off of the inverter / batteries, with the compressor cycling on and off, will the charger potentially keep the batteries charged enough? And will this heavy drain / simultaneous charge, harm the batteries?

I know a 30amp extension cord and transfer switch is simple enough, I just like the retractable reel type extension. Ya know how you get something in your head sometimes? )

Alright... smack me across the face! I can take it!

Thank you!

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Old 01-14-2016, 01:33 PM   #2
Join Date: Dec 2015
Location: Belfast, NY
Posts: 22
Year: 2004
Chassis: Freightliner
Engine: Mercedes diesel
Rated Cap: Handicap bus (approx 30)
I know nothing about making skoolies as I am at the same spot as Ross in my construction. I look forward to more experienced skoolie builders answers.

My plan is to attach my 120vac to a panel and wire in roof top air conditioner and hot water tank to that then wire 120vac to a xantrex unit like this Xantrex Freedom HFS 2000 Inverter Charger Pure Sine Wave 2000W - 55 Amp - 12V: Sports & Outdoors Xantrex Freedom Sw2012 12V 2000 Watt Inverter Charger: Computers & Accessories

and wire a few 120VAC low draw elements (outlets for electronics, tv, radio, fans. Etc) directly to xantrex inverter/charger.

The problem I have doing what you are suggesting is cost. Just to run the air conditioner on inverter I am estimating needing 2000 watts at least in an inverter without anything else running. (bigger inverter/higher cost) I am hoping by wiring the air conditioner and hot water tank prior to inverter I can run on a smaller inverter and smaller converter and still only run Air conditioner on 120VAC.

Anyway I look at it I can't run the Air conditioner without a generator running or being plugged in, short of building a 1000amphr battery system with a big solar system on top. ha Love to hear others thoughts (more experience) on electrical systems design.

Also Ross I have become one with the grinder and the grinder is one with me. ha

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Old 01-15-2016, 12:21 AM   #3
Bus Crazy
Join Date: Feb 2012
Location: Salt Lake City Utah
Posts: 1,330
Year: 2000
Chassis: Blue Bird
Engine: ISC 8.3
Well.... yeah, one could do that. There are trade-offs, of course. None of these make the idea inherently bad or impossible, and for each some people will say "that makes sense for my situation" while others will say "no, that's a deal-killer."

There's the obvious inefficiency (heat) of converting 120 v to 12 v and back again.

The energy reservoir of batteries makes things interesting: that maximum power you can pull from the shore cord is limited by the 20 amp breaker, and also by the amperage of the battery charger. My "big" 40 amp charger draws maybe 5-6 amps from the 120 volt mains for example. The battery bank allows you to consume more instantaneous power in the bus than what is drawn through the shore power cord, but not forever. Eventually you have to reduce power consumption so that the energy refill can catch up.

The best way to figure out whether it can work for your situation is math. You'd have to figure out what amount of power the shore power/charger can provide into the batteries, and figure out how much power, how many minutes, and at what times of day you'll draw it back out. From there you can figure (for example) if the freezer has been running all day, and the A/C comes on in the afternoon, and then we run the induction plate for half an hour to cook dinner in the evening, how enormous does my battery bank have to be so that it won't be discharged too deep? Can the shore power/charger have that bank recharged by morning to start the cycle over again?
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