Building Annie: A Campervan Conversion

[skagitstan]

Then wire it all together. I built the DC cables myself to keep the cabling as short as practical, using 2AWG stranded. The cables to the battery tray are long enough to allow full extension of the tray.

A test of the system with a ~1000W AC load (a pair of halogen work lamps) results in a total .1V drop between the batteries and the MS2012, at a measured battery discharge current of about 78A.


That's about it to this point. Next power system steps are to install the car/house battery VSR interface, and hook up the house AC/DC distribution panel. Then tuck in all the wiring neatly.


Here is a rough block of the wiring setup. Note that the battery monitor (ME-BMK) is not shown connected to the shunt.
Also note the slightly unorthodox fuse hookup. This was done for convenience, since the MPPT 60A fuse assembly came with extremely short leads.

[Boxster1971]

I'm curious why you chose to use such a light weight wire as 2 AWG for your DC connections to a 2000 watt inverter? This is seriously undersized from the recommendations in the Magnum installation manual. I assume you realize that the Magnum MS2012 can draw 267 amps at full output. A minimum of 2/0 AWG is recommended for your setup.

[booster]

Originally Posted by Boxster1971

I'm curious why you chose to use such a light weight wire as 2 AWG for your DC connections to a 2000 watt inverter? This is seriously undersized from the recommendations in the Magnum installation manual. I assume you realize that the Magnum MS2012 can draw 267 amps at full output. A minimum of 2/0 AWG is recommended for your setup.

I would tend to agree, although Magnum is very conservative in their recommendations. I would at least go 1/0. They also say to keep the power wires away from the signal wires as best you can, and even recommend running the pos and neg to the battery strapped together for better efficiency. Very detailed in their wants.

Are you going to have a 12v power relay for the coach, or any battery disconnects, so you don't draw down while sitting if inside and no sun?

[skagitstan]

Here's how I decided that 2GA is OK, in spite of the Magnum manual.

I think wire size needs to be based more on anticipated loads than on how much the power source could ever supply. If I ever expected to draw 267A, then I'd agree with you.

The MS2012 is somewhat overkill for my application. Similar to how Puget Sound Energy full output is overkill to my home electric requirements.

At most, my inverter will see about 1400W load, which assumes a 50% efficiency of my 700W microwave. I will never have two high current loads at once.

Assume the MS2012 is only 85% efficient at that point (based on the Magnum curves). That puts input power at about 1650W, or about 137A input current. If I add another 60A for miscellaneous DC consumption, that puts us at about 200A reasonable worst case draw.

Although the MS2012 is capable of supplying up to 267A, I will not ever be drawing that much without a gross fault. Ampacity tables at 200A call for 2AWG.

My cable run legs that could see the 200A are no more than 8 feet total wire. Lookup tables and my own calculations put the voltage drop at about 4.5%

Boxster & Booster, one thing I will consider based on your points is to add a 225A or so breaker at the battery bank just to be extra safe.

Stan

[Boxster1971]

OK - I thought you were probably going to limit your load to less that max for the MS2012. If you draw 200 A that is right at the recommended limit for 2 AWG wire. Adding fuse or breaker to protect your lighter wire then becomes doubly important so you don't start a fire if you should ever full load the MS2012.

BTW - you might remember that both Booster and I are installing Magnum 2000 watt inverter/chargers in our vans. We've both been pouring over the installation manual. I just finished my battery rack to mount four Lifeline GPL-4CT AGM batteries under my van. Now I'm starting the inverter installation.

You are doing some very nice work on your van. It's inspiring all of us DIYers to press on.

Cheers,
- - Mike

[booster]

That setup is very similar to what we currently have in our Roadtrek, which will be replaced with the new Magnum MS2000 and 4 Lifelines that Boxster mentioned.

We have #2 cables to a 1500 watt Samlex PSW inverter, running off 375ah of Trojan wet cells.

When I built the system, the batteries already had the #2 cables and they showed big enough on the charts, so I reused them. What we have learned since then is that the approximately .5 volts of drop can turn out to be a bit more of an issue than first thought. If the batteries are starting to get down near 50%, the voltage drop from the big use of running the microwave, plus other loads, plus the .5 volts can bounce us off the low voltage cutoff in the inverter. If the batteries are full, or we have the van engine running, it is not an issue because the base voltage is higher, and the drop from load in the batteries is less. When the voltage gets near the low voltage cutoff for the Samlex, the current really goes up compared to operating at normal voltage, in the range of 30% higher.

You have AGMs, so they will drop less voltage, but you don't have as much capacity IIRC, so it is hard to predict what will happen with yours for voltage drop under load. It also will depend on how and when you use the setup, and if the engine is running. As long as you know about it being a possibility, you will be able to watch to see how it goes.

[skagitstan]

Thanks for the comments, guys!

I have about 400AH of AGM, so capacity should be about the same.

I am hoping to avoid running the engine just to recharge the batteries.

Booster, you wrote

Are you going to have a 12v power relay for the coach, or any battery disconnects, so you don't draw down while sitting if inside and no sun?

I'm not quite sure what you are asking.
I will have the VSR to isolate the car and house, unless one of them is in charging mode. I have decided to add that breaker we talked about below, which can also act as an emergency cut-off switch.
The house will (hopefully) always be live, since I will need to keep the compressor fridge going, and may well want to run the lights, house heater or roof fan at any particular time.

I'm using the ME-RC for the SOC and real time power measurements. I'll certainly be keeping a close eye on it as we get familiar with how the system behaves.

Stan

[booster]

Most/many of the units use a 12v bistable relay to turn on the power to the coach from a remote panel. This allows you to shut off all the things that might have parasitic loads like detectors, clocks, etc when you are not using the van. It normally would also kill the frig, but the switch is usually only used when the van is parked and not being used. A separate line could also be run to the frig. We did that, but never have used it.

A main disconnect switch would be right at the batteries so you could kill all the battery power to work on anything without having to disconnect the batteries. It would also be used if you wanted to totally remove all the parasitic on the batteries when stored inside like we do or if you are worried about overcharge off the solar, which can happen with some charge controllers that would put a full charge cycle on already full batteries every day. There is another discussion on the board about where the disconnect should be in relation to the solar controller, and also includes some information about the benefits of having an on/off switch on the solar panels to help prevent voltage spikes.

[skagitstan]

Some bi-stables or SSRs might be useful if we're away from Annie while camping...if the solar can't keep/catch up. I'll have a better idea if needed once we've got a few trips logged in.

Annie parked and not being used is likely to only occur when we're at home or staying at a friend's place, which means shore power will likely be available.

[skagitstan]

Wherein we wire the house and car batteries together. The main question was how to get cable access to the car batteries.


Ford, in their wisdom, decided to store a ~6.7 million Joule energy source (AKA the pair of stock AGM batteries) under the driver's seat .


I had first thought to punch one hole low down in the seat baseBut, the base is slanted (insert political joke here.), and the steel is very hard. I could not get a starter hole drilled.
I found that if I slightly widened one for the covered slots higher up, it would fit a cable and grommet.
So that's where the cables are routing.

I suspect those slot are there in case you have flooded batteries, and need some venting. They are covered inside the base with a plastic sheet.


I added lugs to the seat end of the cables, and roughly determined their placement in the seat base.
Then i fed the other end of the cabled in between the inner and outer side walls. I punched a hole in the inner wall and used a grommet.

Continued running the lines toward the back. When I neaten things up, I will be filling the holes in the rib shown below with expanding foam to keep the cables away fron the metal edges.

I found a convenient hole to get back to the inside world.

[skagitstan]

Wired in the BlueSea ML-ACR relay. (That's the VSR in the last post's block diagram).

Attached the cables to Annie's batteries and neatened up a bit.

Put the seat base back together, and called it a day.


There are two reasons for this interface. One is to allow Annie's alternator to charge the house batteries as we drive. The other is in case Annie's batteries die. I can switch the ML-ACR on and use the house to jumpstart Annie.


I had planned on adding a fuse at Annie's batteries, in case something went awry between the two battery sets. However, the BlueSea instructions explicitly say not to do that if you want to run as a jumper. So, I am not going to do that yet. Also, since it's a real pain to access the under seat battery junctions, if I do add a fuse, it will probably be near the ML-ACR.


Finally, the ML-ACR has a remote control switch. I'm still deciding where I want to install that. It may go in the control/monitor panel I'll be putting in above the fridge.

[Billinnc]

Stan
I'm in the very early stages of building a Promaster based RV and have enjoyed reading your excellent blog. My curiosity also got me to do a little perusal of Sedro-Wooley as I used to live in the SF Bay area and drove north many times.

Could you tell me the rationale for using a 2 AGW ground conductor from your engine battery to your house batteries? It would seem that a good chassis ground at each end would be essentially as functional. I've got to make this decision soon as in my case it will have to go under the floor (house batteries on passenger side). I've pretty much decided to go with 1/0 or 2/0 as charging from the engine alternator (220 amp) is a key part of my energy management strategy. And aside from it being automatic, what is the necessity for going with the expensive Blue Sea relay rather than a resettable breaker?

Thanks, Bill in NC

[skagitstan]

Hi Bill,
The main reason I ran a ground split from the chassis is that I wanted to create (as much as practical) a star grounding system. In other words, the car ground current path and the house ground path are separate.

This is more due to my background designing low noise analog electronics than in any major flaw in using the chassis as the major ground current connection.

Since the house system is otherwise floating from the car system, the star ground may help minimize noise from things like load dumps affecting the house system's behavior.

The reason for the Blue Sea VSR is exactly that it's automatic. It provides for the car to automatically recharge the house (if needed) while driving, or the other way around when plugged into shore while in storage, or to manually let the house provide a jump to the car.

As far as the 220A alternator goes, I'm not too worried about ever seeing 220A flowing through my 2AWG into the house system from the car. There are a few reasons.

• I have a 200A breaker at the house battery. My assumption here is that if it ever was so dead it would accept a 200A charge, something would be seriously wrong, and I would not want the systems linked anyway.
• I don't ever expect to run house functions from the car battery. Certainly nothing that would demand high current.
• Since the systems will be separated when I'm parked (unless the house is in solar charging or shore power modes), I will not need to be concerned about the car getting discharged by normal house functions.
• The alternator would need to be running full tilt to provide that current. Something I'm not likely to do while parked.

Stan

[skagitstan]

The AC and DC fuse/distribution box will be inboard from the water heater. I decided to get the heater mounted before all the cabling gets in the way. Once again, we have a case of needing to do "A" before "B", "B" before "C", and "C" before "A".


The heater is an Atwood propane fired on-demand unit. It needs to be raised above the floor to avoid cutting the plastic outer body panels, and to more or less vertically balance the curvy part of the outer wall.


So, it will sit on a riser box just aft of the propane valves. Here I've marked where we need to slice Annie open. The riser is being used to set the height.

Reasons for choosing this location are that there is a minimum amount of inner wall to cut, and that the inner and outer wall are connected on both sides of the cut pretty close to the hole. That will help keep things rigid.


The inner hole is cut.

Measured and marked for the outer hole, and drilled corner pilot holes.

I cut the hole from the outside. Covered the hole with a bit of plastic sheet because we were expecting rain.

[skagitstan]

Dry fitting the heater, while saving the hole cover for a rainy day. Not sure what the next step would have been if I'd screwed up the cut...

Installing the riser that the heater sits on. The riser is screwed to the floor and VHB'd to the outer wall.

Because of Ford's stupid form before function curves of the sidewall, the vertical center of the heater hits the wall well before the heater top and bottom. In other words, you can't mate the two flush. So, I'm adding aluminum spacers and LOTS of caulking tape to convert the warped sidewall to a more-or-less flat mating surface.
Adding spacers:

Made sure the heater is seated properly. I'll be tying it down with some plumber strap as the last step.

[skagitstan]

Then the caulk tape, non-sag lap sealant, and mounting screws.

Removed a bunch of the excess lap sealant and painted it silver. That sealant stuff is a real pain to work with and finish smoothly. I pretty much failed at the task (as the aesthetics committee made very clear), and will revisit it in some of my copious free time. But for now, it sure won't leak!

[skagitstan]

As an aside, my conversion write-ups (including electrical work) are a bit behind on this site. To many of my entries are picture heavy, and the site only allows 4 pics linked in one post.
One of these days, I'll try to catch up here.
Check my blog if you want the latest blathering.

[skagitstan]

I finally have a blog entry with just 4 pics, so I figured I'd post it up here.
You can also see a bit of the other stuff that got installed, but that I didn't post here (mostly wires).

If you want more details on those other steps, go to the blog.

After installing the fresh water service, we thinsulated the passenger side like the driver side.
Well, almost...the passenger side has the sliding door, which needed a bit more fiddly cutting so insulation didn't hit the latch mechanisms.


Also removed the back doors plastic panels and thinsulated as far as I could reach. Then re-attached the panels.


Got that done, and re-installed the wall coroplast. Of course we needed to cut it to match all the junk we've added.


Not much more to say, except here are a few pictures.


Since the thinsulate is glued to Annie's outer wall, there is an air gap. That means Reflectix should actually work here. Glued it to the coroplast panels.


Cut the panels down in height to accommodate our 2" raised floor

I also cut a hole in the panel facing the MS2012 exhaust fan, to make sure the panel wouldn't block ventilation.


Tomorrow, we start figuring out ceiling lighting...how many lamps, spacing, and deciding if they should be on a dimmer.


Stan