Installing an Inverter in your Minivan RV

Installation kit for RV inverter

If you want to run 120-volt appliances in your minivan or micro-camper, you will need at minimum, an inverter.  You may also want to add a “house battery” to your system later on.  This post will help you to build a scalable system.

After I decided to hit the road in a Minivan RV, my second thought (after the bed) was power.  I wanted to be able to run up to 800W of 120v appliances, so I set about setting up an inverter.  Inverters convert your 12 volt (12v) battery voltage to 120 volts (120v) to run household appliances.  My plan was to run a 300W immersion heater to heat soups and make coffee.  I set a budget of $100 for the project, but did it for $60.

I settled on this inverter from Amazon, which turned out to work fine, but I’ve since found better options (see “Lessons Learned” below).

I chose 4 awg wire for the install (explained in Lessons Learned) and found some really cool connection lugs in the car audio section of Amazon.

No solder lugs.  A real timesaver!

These lugs are helpful because you can make your connections without soldering the connections.  There is so much mass in a 4 ga wire plus lug that you really need a propane torch or LARGE soldering iron to do the job.  I think these lugs are a better option.

The last part of the puzzle was the fuse.  You always want to fuse anything electrical that you add to your van.  Ideally, you place the fuse as close to the battery as possible, so that if anything goes wrong, only the wire between the fuse and the battery will melt or catch fire.  You don’t want to place the fuse at the end of the line or the wire can melt down ANYWHERE along the way.  After searching fuses, I found a better solution.

These little circuit breakers can be reset and do not require you to carry extra fuses.  They also have a neat disconnect button for when you need to service the inverter and battery pack. 

Note that I actually used a 100A breaker, but for reasons outlined below, I have provided a link to the 60A unit, so nobody buys the wrong one.

How to Install

This section is incomplete as of 11/13/17 because I want to add more detail, which takes time.  There will be a video later, which details the installation.  Check back later or follow us on Facebook @OdysseyCamper, for updates.

microcamper inverter how to
4 awg car audio cable was used for the install. It has a lot of individual conductors, which makes it very flexible.
Connecting the inverter to the starter battery
Power strip for 12V inverter
The 800W inverter easily powers my 300W (here) and larger immersion heaters.

System Use

Everything is a compromise.  With just an inverter your options for power usage are limited (that’s why part 2 is about a battery bank).  At the completion of the project, I had 800W of continuous 120V to run my immersion heaters and fans.  Keep in mind that your vehicle battery is only about 40Ah (ampere/hours) so a 300W heater will run it down to 50% in about 45 min.  It takes about 10 min to heat water to boiling, so I am able to make a French Press of coffee and a bowl of oatmeal (two batches of water) without starting the van.  However, if you are going to be parked for a couple days, it’s a good idea to start the engine before using the inverter, to avoid killing the battery.

Lessons Learned

In the course of the project and as a result of further research, I learned the following lessons that you may want to take advantage of.

  1. The inverter listed above will work, but I’ve since discovered that Whistler brand inverters will support twice their power rating for up to 10 seconds.  Without getting too complicated, this allows you to start appliances with a higher current draw (like a refrigerator) at startup.  So, to do it again, I would pick one of the following two (unless running an electric blanket (see point two, below)

  2. The inverters above will run ALMOST any appliance of the same or lower wattage, but there is an exception.  While writing a review on an electric blanket for RVs use, I discovered that electric blanket controllers do not like modified sine wave converters.  They require a “pure sine wave” inverter.  It would take too much space here to explain the difference, but you can Google it.  I have since purchased the following inverter for PHASE 2 of my minivan build out.  It has received an “A” rating from and is running great so far.  If you never plan to run an electric blanket, get the cheaper Whister unit.  Otherwise, I suggest this one.

  3. A 100A circuit breaker is too big (allows too much current) for my application.  I was anticipating a higher current load when I initially bought the breaker, but it would wiser to limit the current through a 4 gauge wire to 60A, according to the US National Electrical Code.
  4. The high load I was anticipating was going to charge a house battery, but I forgot the 20% rule of charging lead-acid batteries.  That is, your charging current should only be 20% of the total battery Amp/Hr capacity.  For my intended system of 200Ah, 40A would be sufficient (200x .2=40) through a battery charger (turns out that 40A chargers are harder to find, so I settled on 30A).  I was thinking, “these batteries are going to pull MAJOR current when they charge”, but that’s not the right way to do it.  For optimum battery life on a deep cycle lead-acid battery, you need to charge slower.  This is a common mistake that people make when installing a house battery and using an isolator.  The isolator prevents the house battery from pulling current from the starter battery, but it can allow the battery to charge too quickly for optimum life span.
  5. If you are only ever going to run the inverter, then this system with 4 gauge wire and a 60A circuit breaker is fine.  However, if you are designing a battery and inverter system and not stopping along the way at JUST an inverter, it would be wiser to use much less expensive 10 ga wire and a 40A circuit breaker.  This is because you will be using a separate  charger to replenish the battery and it is never going to pull over 30A or so.

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