My Promaster Van Build: Rear Entry, Hidden Bath/Shower, and a Few Other Unusual Details

Page 9: Electrical System

Note: I am only showing my electrical system to document it. It is not meant to be a comprehensive guide to designing and installing your own system, which is why I have left out issues of determining loads, cable sizing, type of cable/wire used, wire connections, etc. There are many resources that can provide the specific details of the options and methods. Gary’s site has a lot of excellent details as well as links to other resources.

 

I will get back to the plumbing later, as I’m going to follow my build chronologically, which means the actual electrical system build comes first.

I followed Gary’s electrical system build at buildagreenrv.com very closely, as he’s come up with a very pragmatic and effective plan. I’m going to borrow his system diagram (above) if he doesn’t mind. The heart of it is a pair of Interstate 6 volt golf cart flooded lead acid (“FLA”) batteries, which are cheap ($168 for both at Costco). Their capacity is 220 amp-hour, but one doesn’t want to use too much of that capacity, as that reduces their life.

There are more expensive AGM lead acid batteries, but the difference doesn’t seem worth it. And of course there are a growing number of lithium ion batteries and system available, but they’re still expensive. If one has a very demanding electrical load, as some fancy vans do, with a/c, electric heat, cooking, etc., then a lithium system may be necessary. But for a basic van, this is the most cost effective.

Gary’s electrical pages cover in great detail determining total electrical loads and therefore sizing the electrical system.

As is clear form the diagram, the batteries are charged either from the solar panel via the MPPT charge controller, the van engine’s alternator, via a battery isolator to keep the van battery from being drained down by the house system loads, or from shore power (120V) via an extension cord to the inverter/charger. There’s also a lot of debate about how these three charging systems interact with each other, but they seem to get along just fine unless one chooses to worry about that sort of thing.

I showed it earlier, but here’s the front panel of my electric system box. Clockwise, starting with the large black panel, which is the AC/DC distribution/breaker/fuse box. The four rocker switches turn off a few key circuits without having to open the breaker box. The white unit is a propane detector, mounted close to the floor as propane is heavier than air. Below it is the Xantrex inverter control panel, and on the lower left is the solar charge/controller, a Midnight Kid. The Victron battery monitor panel is up in a remote location, in the overhead compartments.

The electrical box has a base of 3/4″ plywood, attached securely by bolts, one of which screws into one of the cargo retaining rings and the other goes through the floor. The battery box sides are also 3/4″, and the other sides are 1/2″ plywood.

The battery box was made strong to secure them in case of a crash. I bought a chunk of EPDM pond liner which is folded up on the sides, the corners glued with caulk.

I built my battery cables from 2/0 gauge flexible copper welding wire, various appropriate sized copper lugs, and a Temco hammer lug crimping tool.

I’m not going to go into detail on the various sized wires/cables appropriate for each subsystem, as Gary’s pages have a lot of useful info on sizing. I bought various sized breakers and mounted them on the inside of the electrical box, this one is for the solar charger output.

This is the main 200 amp DC breaker for the battery output to the inverter. I initially had a cheaper 250A breaker there, but it didn’t allow enough current flow when using the 700W (120V) microwave, shutting down the inverter due to it sensing a low battery voltage. I was a bit dismayed by that, but swapping in this better T Tocas unit fixed the problem.

And a 60A breaker for the line from the van engine alternator (it’s also protected at the battery by a fuse). I initially had a 50A breaker here, but it kept popping right after I started the engine in the morning, so apparently the demand from the house batteries exceeded that amount initially, or it was a bad breaker (these are all cheap imports). I replaced it with a 60A breaker, which solved the problem and does not exceed the safe limits of that cable.

These two minor breaker issues were the only ones I encountered, very early on. Otherwise the system has been utterly problem-free.

Since I was going to be using a 120V fridge, and wanted enough power for 120V power tools, I bought a more powerful inverter than I would have needed otherwise. The Xantrex 807-2055 ($800 then; cheaper now) is a high quality pure sine wave inverter, which means electronic equipment can be used. it’s rated at 1000W continuous/2000W peak power. My only very minor complaint is that whenever the fridge initially kicks on, the momentary compressor load is enough to start the inverter’s fan for about one second as it anticipates (wrongly) a heavy load. As the electrical system is under my head under the bed, it bothered me some the first night out, but I’ve long tuned it out.

The inverter is securely bolted to the 3/4″ floor of the electrical box. I’m not proud of the organization of my electric wires and cables, but since I was making this up as I went along, it’s just the way it is. I used 14 gauge Romex cable for all the AC runs as well as a number of 12V DC runs, with the bare copper ground not used in that case.

Understanding how these combined AC/DC systems work in terms of chassis ground and its relationship to possible shore power ground is important.

The Inverter/Charger control panel displays the current battery voltage, among other things. Yes, with a full charge and resting, 12V batteries actually have as much as the 13.7 volts as displayed here (I set my charge voltages according to specs from Interstate). But that drops almost instantly as soon as there is a load, and high loads drop that down into the 11 volt range.

I decided to add a Victron BMV-700 battery monitor ($143), to be able to keep a close tabs on the SOC (state of charge) of my batteries. It’s not necessary, but it’s nice to know they’re not getting drawn down to far and that everything is working. The only way I found out that the breaker from the van alternator was popping upon start-up was that my SOC was not going up after a drive in the mornings.

It measures the flow through the negative (ground) flow, so requires this shunt. All negative cables need to be connected to one side, and the battery to the other.

This is the PD 5000 ($86) AC (left) and DC (right) breaker/fuse box. In retrospect, I might have gone slightly overboard on the AC outlets, but the cost of a bit more cable and a few more outlets was minor.

I had a problem with the AC breakers not seating properly on the hot bus bars, causing them to arc or not work at all. I had to take some pliers and bend the bars to the left to fix that.

This is the MidNite Kid Solar MPPT (Maximum Power Point Tracking) solar charge controller ($290). It can handle more than the single panel I currently have. In fact, a single full-size panel is about the minimum it can utilize. Note: this system does not use the quite common smaller 12V RV/portable type panels, which do not require this type of charge controller. The residential/commercial large panels put out some 30-38 volts, more or less.

Given that we tend to not spend a lot of time in any one place, having a 300W solar system is somewhat questionable. Our modest loads on the batteries would be ok for 2-3 days. But I decided to incorporate solar from the get-go, and I suspect it will come in handy in the future at some point. If nothing else, if we survive the inevitable The Really Big Earthquake in the northwest, our van will be handy as a self-contained living pod with solar power.

The PAC-200 battery isolator disconnects the van battery from the house system, so as not to drain it. As soon as the ignition is turned on, the relay inside closes the circuit so that the charge form the alternator can now charge the battery. It requires an ignition-controlled 12V source, which fortunately was not far away in a 12V van power outlet in the passenger side rear corner.

The yellow cable is an extension cord that runs from the inverter to the shore power receptacle.

I routed the cord out the passenger side rear corner through an existing body opening, and then inside the rear bumper frame to an outlet on the driver’s side of the bumper. That avoided one more hole in the van body. To date, I’ve never used shore power, but perhaps one of these days.

Continue to Page 10 for Refrigerator, Furnace and Propane System

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