Second Battery and Inverter Install Volkswagen Bus

If you are going to be overlanding for any length of time, this is a modification that I highly recommend for any vehicle.  Electrical things are kind of intimidating for many of us, me included, because we are afraid of starting an electrical fire, shocking ourselves, and any number of other horrible outcomes to doing something wrong with electricity.  But if you think doing this is beyond your skill set, it probably isn’t.  The wiring is actually relatively simple, even for people that don’t know electricity.  It is a bit labor intensive and if you’ve never used a blow torch before, like me, you are going to be learning some great new skills.


A quick overview of the project:

Install a 2000 watt inverter and a deep cycle battery to run it.  Setup the vehicle to be able to charge either battery or both.



  1. Electrical wire of different gauges, copper welders wire seems to be the best stuff to use.  Gauges and lengths depend on where you are putting things and also how much power you need to be able to run through the wire.

    The Perko Switch is pretty straight forward.

    The Perko Switch is pretty straight forward.

  2. 1 Perko Switch also called a battery isolator
  3. 2 battery terminals
  4. At least 12 lug connectors
  5. At least 12 soldering slugs
  6. At least 12 pieces of heat shrink tubing
  7. Flux
  8. 1 Fuse
  9. 1 Fuse holder



  1. Wire snips capable of cutting the gauge wire you are using
  2. Blow torch
  3. Drill with bit bigger than diameter of the wire
  4. Vice or something else that can hold a burning hot lug connector in place while you jam a cable into it.
  5. Tape measure
  6. Wrenches and/or pliers to tighten terminals to battery and inverter post
  7. cable stripper or razor blade


The main reason this project is time consuming is that you have to make lots of cables and each cable needs either a battery terminal or a lug connector on either end.  Because you need them to be the right lengths without a bunch of extra cable buying pre-made ones is not an option.  This project is just measuring lengths of cables needed, drilling holes to run cables and making the cable list below.  Determining the cable gauge is a matter of length and amperage running through the cable.  There are charts all over for this and you can always go thicker than you need, you just can’t go thinner.

I chose to install the inverter on the side of the closet.  That way I could run cables through the closet and my electricity was more or less central.

I chose to install the inverter on the side of the closet. That way I could run cables through the closet and my electricity was more or less central.

3 outlets and a USB

3 outlets and a USB









How to make the cables Click for video

From the second battery you will need to make a cable from:

  1. Positive battery post to a fuse of appropriate amps in a fuse holder.  (Battery terminal one end lug connector other end.)
  2. Fuse to positive inverter post. (Lug connector both ends.)
  3. Positive battery post to Perko switch “battery 2” post. (Lug connector both ends)
  4. Negative battery post to vehicle chassis. (Battery terminal one end lug connector other end.)
  5. Negative battery post to negative inverter post. (Lug connector both ends)


From the first battery you will need to make only one cable.

  1. Positive battery post to Perko switch “battery 1” post. (Lug connector both ends)


Then there is one additional cable that needs to be made.

  1. “Common” post on Perko switch to voltage regulator. (Lug connector both ends… sort of) This is where things get a little different on an old bus compared to newer vehicles.  Most newer cars would need this cable to go directly to the alternator because it is already internally regulated.  When you start the project you should be able to figure out where this cable should connect by following an existing wire from your battery to the regulator (or alternator if you have a newer car).  This is also, where I had to do some problem solving.  The Voltage regulator accepts a spade style connector not a lug style, but they don’t seem to make spades that are large enough for the gauge wires I was using.  Solution… Solder spade onto the lug connector and move forward.  More on how this comes back to bite me in the Blog section.


You will likely need to ground your inverter to the chassis with another cable.  your inverter instructions should tell you more about it.

There is also another Cable that can be made if you choose to make it, but isn’t required.  You can replace the cable from battery 1 to starter with a cable from “common” on the Perko switch to starter.  This will allow you to start and run the bus and its accessories from either battery.  Also, turning the Perko switch to off would act as a kill switch because the ignition switch would be interrupted.  I wish I had made this cable before heading out to Alaska.  Being able to run off of the second battery would have been great.

Leave a Reply

Your email address will not be published. Required fields are marked *