Installing an auxiliary battery in your van is a great way to make camping more comfortable without the risk of killing your starting battery and leaving you stranded. There are many different ways to set up an auxiliary power system in your van, some are fairly simple and straightforward and others are so complex that the average DIY mechanic will quickly get in over his head.
Over the years I have seen all sorts of different setups and have worked with people to make a simple and dependable solution to add an auxiliary battery under the passenger side of the rear seat. This battery location helps to balance the weight of the cabinets in a full camper and also offers a very short charging path that reduces voltage drop and increases charging efficiency.
Since every installation tends to be a little bit different, I devised a "semi-custom" list of materials that contains enough wire to allow for several different wiring paths. This allows the installer to work around any obstacles that may already be present under the rear seat (heaters, amplifiers, inverters etc).
Due to the multitude of different system possibilities, step by step installation instructions are impossible. There are tons of great posts on www.thesamba.com and the community of Vanagon enthusiasts there can definitely help you sort out the details. If you have never worked with automotive wiring before, please have a professional do the battery installation for you. Heavy gauge wire carries a lot of current and can start a fire if you don't use good work practices.
To complete the installation, you will need access to a few basic tools listed here.
The following list of materials designed for use with a Group 31 deep cycle battery, the Blue Sea Systems ACR 7610 and Blue Sea System 5029 (12 circuit) or 5025 (6 circuit) fuse block installed under the passenger side of rear seat.
Positive connection from starter to ACR & ACR to auxiliary battery (available in 6AWG or 8AWG):
Tinned Marine Wire (Red) x 7' (cable supplied in a single 10' length to reduce waste during installation)
3/8" Ring Terminal (ACR) x 2pcs
5/16" Heavy Duty Battery Lug (Starter)
5/16" Ring Terminal (Aux battery positive post)
MIDI Fuse Holder with fuse (Aux battery +)
#10 Ring Terminal (x 2pcs for MIDI fuse holder)
Rubber Grommet
Corrugated Protective Wire Loom x 6' (protects power wire from starter to ACR)
Ground connection from ACR to seat belt bolt:
12AWG Wire (Black) x 3'
12/10AWG x 1/4" Female Disconnect Terminal (ACR ground tab)
12/10AWG x 1/2" Ring Terminal (seat belt bolt)
Ground connection from auxiliary battery to seat belt bolt: (available in 6AWG or 8AWG):
Tinned Marine Wire (Black) x 3'
5/16" Ring Terminal (battery negative post)
1/2" Ring Terminal (seat belt bolt)
1/2" Star Washer (install between ring terminal and chassis)
Positive connection from auxiliary battery to fuse block: (available in 6AWG or 8AWG):
Tinned Marine Wire (Red) x 3'
5/16" Ring Terminal x 2pcs
MIDI Fuse Holder with fuse (Aux battery +)
#10 Ring Terminal (x 2pcs for MIDI fuse holder)
Supplies to complete installation from fuse block to accessories:
12AWG Red Automotive Wire x 25'
Adhesive Lined Shrink Wrap (3:1) 1/4" x 12"
Adhesive Lined Shrink Wrap (3:1) 3/8" x 12"
12/10 AWG x #10 Ring Terminal (fuse block connections)
12/10AWG 1/4" Female Disconnect Terminal (most common accessory terminal)