The Electrical System

This section covers what a camper van or RV electrical system does, how it works, how to pick and size the components, and how to build the system.

Safety Warning and Disclaimer

There are serious safety issues involved with wiring your own system. The voltages are high, and potentially lethal. Doing the system incorrectly can lead to serious consequences down the road. PV systems have the added hazard that even when the grid power is turned off, the system can be “live” and present a serious shock hazard.

If you don’t feel like you want to put in the time to learn how to do this correctly, then find an electrician that you can partner with to do this part.

I want to make it very clear that I am not an electrician, and I take no responsibility whatever for the correctness of the material below — you need to do your own homework!

This is a picture showing most of the components for van conversion electrical system.

Two systems are described: 1) a simple, small self-contained systems for minimalist camping, and 2) our system, which has more functions and more capacity, but still very buildible.

Overview of an RV Electrical System

The diagram below shows the electrical system for our conversion. It turns out to be a pretty generic diagram for any camper van electrical system. Your system may not have all of the functions shown — e.g. you might chose not to have solar charging, or not to provide for 120 VAC loads, but the diagram will look about the same except with the parts associated with those functions removed.

If you want to do your own circuit diagram, Digikey Schem-It is a nice, free diagraming tool — wish I had found it before doing the diagrams below 🙂

At the heart of the camper electrical system is the house battery. It provides power for the things you are running in the RV. It needs to be charged up to provide this power, and for the system shown, it can receive charge from three separate sources: 1) the van alternator when the engine is running, 2) the roof mounted solar panel when he sun is shining, and 3) the inverter/charger when plugged in to shore power. Besides charging the battery, the other major function of the electrical system is to distribute power safely to the various RV loads.

A quick over view of what the major components do:

The House Battery provides electrical energy to power your RV electrical loads.

The Inverter converts 12 volt DC battery power into 120 volt AC house power to power loads that require house power (eg a microwave). In this system, the Inverter and the Charger are combined into one unit.

The Charger charges the battery when you are plugged into “shore power” — that is, from 120 volt AC provided by the campground or RV park (or any kind of 120 VAC outlet you can find at your house or a friends house).

The PV panel and Charge Controller charge the battery from the sun. The Charge Controller regulates the charging voltage and keeps the PV panel from overcharging the battery.

The Battery Isolator connects the regular van alternator and battery to the house battery only when the van engine is running so that the van can charge the house battery. When the van is not running, it disconnects the van battery from the house battery to insure that RV loads cannot run down the van battery and leave you stuck.

The AC Breaker Panel distributes the 120 volt AC power from the inverter (or shore power) and distributes it to you 120 volt loads — it includes circuit breakers for each circuit to protect the wiring.

The DC Fuse Panel distributes 12 volt DC power to all or your RV DC loads (eg lights, fridge,…) — it includes fuses for each circuit to protect the wiring.

The diagrams for most RV’s will look pretty much like this. However, the actual components may be quite different. A small, simple van conversion might have everything combined in something like a single ArkPak box that has everything built into one compact and easy to install box. A larger RV might have half a dozen 100 lb batteries and a components that take up a whole cabinet with lots of point to point wiring. I’ll describe a very simple system and a more complex one (ours) in more detail below.

I don’t discuss generators anywhere because I don’t like them 🙂

Estimating Electrical Demand

Before you can select your components and start building, you need to identify what electrical loads you want to run, how much power they use, and how long you want to run them. You also need to estimate how long you want to be able to camp away from “shore power” — that is, how long your battery has to power the loads.

I’ve put together a separate page on estimating RV electrical demand …

The page will help you decide how large a battery you need, what size Inverter/Charger you need, and what size solar charging system you need (if any).

Choosing Components

This section provides a little advice on picking some of the components for the electrical system. The page on sizing the components for your needs might also be useful.

Our ProMaster camper van conversion has an electrical page that provides a lot of detail on our electrical installation which may be helpful.

Batteries

You will have to choose what type of battery you want to use in your conversion. In any case, you will want to choose a deep cycle battery — this is a battery that is designed to be discharged deeply again and again. Ordinary car batteries are not deep cycle, and will not stand up to service as an RV battery.

Your main choice for house battery will be between two types of lead-acid deep cycle batteries: 1) the conventional flooded lead acid battery, and 2) the AGM (Absorbed Glass Mat) battery. There are a lot of pros and cons between the two, and I’ve put together a separate page that may help with the decision…

Another alternative that is seeing more use lately is the Lithium battery, and the link above includes some information on using Lithium batteries.

For batteries mounted inside the van, the batteries will need to be mounted in a strong box which is bolted through the floor so that the batteries do not become a missile in a crash. If FLA (Flooded Lead Acid) batteries are used, the battery box must be vented to the outside to vent off any Hydrogen produced during charging. There is a potential explosion hazard if it is not vented.

In some cases, batteries are mounted under the van. This link shows an under floor battery mounting.

It seems like an AGM battery might be a good choice for this kind of installation as checking water level and adding water is going to be difficult even with the jacking arrangement he has.

Update: Ran across this recessed battery box on the ProMaster forum. Seems like a good solution in that it frees up some space without exposing the battery to the weather, mud etc of an underbody mount. It also provides nice easy access to the battery from above. Not sure about other vans, but on the ProMaster, there are only a limited number of places that this box will fit, so some early planning is in order if you want to use it.

You will want to have a way to monitor (at least roughly) the charge status of the house batteries. An easy way to include a small digital volt meter that you can check. The voltage of a lead acid battery at rest depends on its state of charge, so you can get a rough idea what the state of charge is by checking the voltage — its pretty rough, but much better than nothing. Another approach is to use a charge monitoring system (e.g. TriMetric) that gives a precise reading on how much is left in the battery at any time.

Inverter/Charger or Power Converter

A lot of camper vans these days use a combined inverter and charger unit. When you are hooked up to shore power, this device charges your house battery and supplies 120 VAC power to the gadgets in your RV that require regular household power. When you are away from shore power, the same unit has an inverter which supplies 120 VAC power to the RV from the house battery. This Trip-Lite is one example.

I like this kind of inverter/charger approach because: 1) it eliminates the need for a separate battery charger to charge from shore power, 2) it has 3 stage charging, so its easy on the battery, 3) it automatically switches from the inverter powering AC loads to the shore power when you plug into shore power, so you can hook your AC loads up to the inverter and they will be powered whether you are on shore power or on house battery power.

Update 1/1/2016: One thing I’ve noticed is that pure sine wave inverter/chargers have dropped in price some, so if you plan to run AC loads that might need the pure sine wave output, you might want to upgrade to a pure sine wave inverter — one example is the Xantrex Freedom HFS 2000 Inveter Charger.

The other approach is to use a Power Converter (basically a battery charger and DC power supply). While hooked to shore power, the power converter can charge your house battery and supply 12 volt DC power to your 12 volt RV loads. Best Converter offers some options. It is good to have a true three stage battery charger that can be setup for either AGM or FLA batteries and provides separate stages for bulk, absorb, and float charging — a good charger is probably the main factor in not killing your batteries before their time (which is very common).

Its good to have a way to turn off or disconnect the inverter when it is not in use because it draws some power even when just sitting there doing nothing, and this is an overnight drain on the house batteries.

Solar Charging

Solar charging allows you to charge the house battery using photo voltaic panels mounted on the roof (or elsewhere) of the van. The advantages include: 1) being able to charge your house battery without having to run the van engine when you are camping at a spot that does not have shore power, 2) keeping the house batteries healthy and charged when you are at home without having to have the camper plugged into the house, and 3) saving some energy (especially if you are a full timer or do a lot of RVing).

The Solar charging system consists of one or more PV panels and a charge controller. The charge controller goes between the PV panels and the house battery — it increases the efficiency of the solar charging, and (most important) does not allow your PV panel to overcharge (and destroy) your battery.

The diagram shows the part of the electrical system diagram that provides solar charging for the house battery on our system.

There are a couple of decisions to make in designing and building a solar charging system, and some tools that are helpful — I’ve done a separate page on solar charging systems here…

Charging from Van

The diagram below shows just the part of the electrical system for charging the house battery from the van charging system.

Most systems provide for charging the house battery from the van alternator. This just consists of running a wire from the van battery to the house battery. This wire should be large enough to carry the maximum charging current anticipated, and the wire should be protected by fuses on both ends — that is a fuse in the wire near the van battery and another fuse in the wire near the house battery. Two fuses are required because you have a large source of power at both ends of the wire. In addition, a Battery Isolator is normally used in the wire between the van and house battery. The fuses should be as close to their respective batteries as possible — fuses such as the Mega Fuse allow the fuse to be connected directly to the battery terminal or bus.

Lead acid batteries should not be charged at more than C/10 to C/5 where C is the rated capacity of the battery in amp-hrs. So, for our 220 amp-hr battery the maximum charging current is about 33 amps. We used a 50 amp breaker in the charging line so if the batteries are being charged at too high a rate the breaker would trip and alert us.

The Isolator disconnects the house battery from the van battery except when the engine is running — this keeps you from accidentally discharging the van battery to the point where it cannot start the van. The VSR (Voltage Sensing Relay) is an alternative to the Battery Isolator that works just as well and is easier to hook up. It is also possible to just have a manual battery cutoff switch in place of the Battery Isolator, but you have to remember to turn the switch off and on at appropriate times. Its not such a bad idea to have the manual cutoff switch in addition to the Battery Isolator in that it gives you the ability to disconnect the house battery from the van charging system (say when you are on solar or shore power).

See the sizing page for sizing these components…

Battery Monitoring System

A Battery Monitoring System is an optional gadget that basically tells you accurately how much juice is left in the battery.

We recently added a Victron battery monitor to our conversion — full details here…

Wiring in the battery monitor requires adding a shunt to negative terminal of the battery, so if you think you may want to install a battery monitor at some point in the future, I would reserve a space for the shunt near the negative terminal of the house battery — the link above shows what the shunt looks like.

Wiring

For the DC circuits on camper vans, many conversions use ordinary Romex house wire. The Romex style wire is readily available, easy to work with, and provides the outer protective plastic cover that helps to protect the wire. The sizing page provides some tools that help you choose what size wire to use. The wiring for our conversion used nearly all of one 250 coil of #13 Romex plus a few feet of #12 Romex.

Some sources advise the use of stranded wire for RV’s in that it is more flexible and better able to take the stresses imposed in the moving vehicle environment. Something to think about, but the solid Romex style wire is widely used.

For a few places where heavier wire was needed, I used THHN stranded wire from Lowes. I used this heavier wire on: the inverter to battery run, the DC panel to battery, and the van to house battery wires. I bought the wire at Lowes — they charge a lot per foot, but they will sell you exactly what you need cut off a large coil.

Each DC circuit must be protected by a fuse or breaker of the appropriate size. A distribution panel of some type will be required to mount the fuses. The panel we used provides both AC and DC distribution in a single fairly compact unit. The number of DC circuits seems to grow and grow as you get into the build, so I would try to get a distribution panel with more circuits than you think you will need. Our panel provides 12 DC circuits, and we are down to having only 2 spares at this point.

For AC circuits, the same Romex wire can be used. Most camper vans don’t have a lot of AC circuits, so wiring tends to be minimal. The AC wiring must, of course, be protected with AC circuit breakers. A distribution panel of some type will be required to mount the master and branch circuit breakers. The panel we used provides both AC and DC distribution in a single fairly compact unit.

Some wiring hints:

When insulating, think about where you will want to run the wiring and leave space (or do the wiring first)

Clearly mark both ends of each wire with what load it serves (e.g. galley lights) — this will save a lot of puzzling when you got to hook them up.

Where wires go through places where they could be abraded, cover with flex conduit.

See the sizing page for wire sizing detials…

Some Example Systems

A Really Simple and Portable System

If you just want to do simple camping with a few small loads, this kind of system might be good for you.

It consists of a heavy duty box that holds the battery, and built into the box are:

A small inverter to for minimal AC loads (maybe a small TV or ?) A couple cigar lighter style 12 volt outlets to power A built in charger with control panel to show battery status. A built in battery isolation switch.

An example of this kind of system is the ArkPak… This one appears to be well made, if a bit pricey, but I’m sure there are other systems out there, or you can build the system yourself using off the shelf components — see below.

Depending on the battery size you pick to go in the box, this kind of system will be able to power: a few LED lights, a radio, a laptop, a fan, and things that plug into a USB port for charging — quite a bit.

It will not give good results for things like: a typical electric RV fridge, any kind of electric resistance cooking, a microwave, an RV air conditioner, a hair dryer, … With these loads, it would not run at all, or would very short battery life.

Some loads that it would be marginal on include an efficient electric fridge (eg one using an efficient Danfoss compressor) — 40 amp-hrs a day, A propane furnace with an efficient blower — about 25 amp-hours a day.

If you used the largest battery it takes (130 amp-hrs), and you discharge the batter to 20%, then you have about 100 amp-hrs available. So, with just the small loads, you might get a couple days out of the battery without charging, but if you had one the larger loads plus regular loads, it would likely need recharging each day.

This is the data on an AGM battery Trojan group 31 AGM battery… This is a 100 amp-hr battery — could not find a 130 ah AGM.

A nice feature of this system is that you can pick the whole thing up and carry it to (say) a tent or outside use. It would also provide a little backup power for power outages a home.

You could buy the individual pieces (battery box, small inverter, sockets, disconnect switch, small charger, and wire) and put something with the same functionality together yourself for substantially less money (see next system), but it is nice to have all of it packaged for you.

Another Simple System

The Yeti 1000 system is another option along the same lines as the ArcPak, but it uses a Lithium battery and provides more more life — it would meet the electrical needs of many van conversions.

In one 42 lb box that measures 10 by 15 by 14 inches, they provide a 1000 watt-hr (83 amp-hr) LI battery, 1500 watt pure sine inverter, PWM solar charge controller, battery monitor system, AC outlets and DC outlets, and USB charger outlets.

It will charge from solar panels, 12 volts DC(eg from the van), and/or AC shore power. It costs about $900 at Costco.

Seems like this might make a nice solution for someone who wants a very simple, all in one box electrical system for a conversion. It could be mounted in such a way that the outlets are directly accessible to plug things into. Or, it could be enclosed and your run a little wiring from its plugs to outlets anywhere in the RV. It could be installed in such a way that it could be removed easily and used outside while camping, or as emergency power for a power outage in your home.

It can be solar charged and is capable of handling as much as 360 watts of solar — more than you will likely need. But, as Matt from the ProMaster Forum points out, charging on shore power is slow as the charger provided is low in capacity — a full charge is going to take overnight (maybe more).

They list the battery type as Li ion NMC, so not the LiFEPO4 used in a lot of RV conversions. They list the life as “hundreds of cycles”, not the thousands of cycle claims you usually see for LI van batteries — maybe they are just being conservative (or realistic) in the life claim. Maybe someone knows how the these two Li chemistries compare?

There is also a larger version called the Yeti 1400, and they also make an lead acid AGM version.

I know all of us that have slogged through the usual RV electrical system component selection, wire sizing, fusing, grounding issues… would never consider such an easy solution — or would we

Another Simple DIY SystemWith Solar

This is also a nice simple system like the one above, but with quite a bit more capacity and with a large capacity solar array to charge it, and a low cost.

The system components are:

Four 80 watt monocrystalline PV panels for 320 watts total of PV power. Four 12 volt, 95 amp-hour AGM Batteries. Two 10 amp charge controllers and fuse blocks. Assorted cables and wiring.

An inverter will be added to the system when 120 VAC “house” power is needed.

Note that this systems is basically built as two identical and independent systems resulting in quite a bit of capacity — one could just build one of the systems for a total of about $330 in parts including solar charging.

All the details on this system….

More small, standalone solar powered systems from my Build It Solar site — most of these could be adapted easily for camper van use…

A More Complicated System

This is the system we used in our ProMaster camper van conversion. It is the system shown in the diagram near the top of this page.

It uses two 6 volt golf cart batteries for power, providing 220 amp-hrs (175 amp-hrs usable) capacity. It can be charged from three sources: 1) the van alternator, 2) the solar panel on the roof, and 3) the charger that operates from shore power. It supports twelve DC circuits with fuse protection. It has a combination battery charger and inverter — the charger provides battery charging when plugged into shore power, and the inverter provides power for 120VAC loads when shore power is not available. The distribution panel used provides for twelve DC circuits and two AC circuits — just about right for a lot of camper van conversions.

LOTS of detail on this system here…