Vanagon Auxiliary Battery Installation
Rear Seat Mounting Location using Blue Sea Systems
ACR 7610 and Blue Sea Systems Fuse Block
Placing the auxiliary battery (or batteries) in the space below the rear seat is an ideal location in terms of secure mounting and ease of electrical connection. By using terminal #30 (the 8mm post) on the starter solenoid as the power source for the auxiliary battery, the length of the power supply wire can be as short as 36". This short run of wire helps to reduce voltage drop from the charging source to the battery.
A single hole must be drilled through the body of the van to run the power wire from the starter post to the inside of the van. Locate the hole where it will allow the wire to enter near the positive post of your auxiliary battery. Install a rubber grommet into the hole to protect the wire. The power supply wire should be completely covered with protective loom so it won’t be damaged by road debris.
The Blue Sea Systems ACR 7610 is a Bi-Direcional automatic charging relay. It can handle up to 120A of constant current. Using the ACR to control the charge to your auxiliary battery is simple and efficient. There are only three basic connections necessary to hook up the Blue Sea Systems 7610 ACR:
1) 8AWG (or larger) wire carrying 12V+ from the starter post (5/16“ ring terminal) to either one of the 3/8" posts on the ACR.
2) Wire (use the same gauge wire as the wire coming from the starter post) from the other 3/8" post on the ACR to the auxiliary battery positive (+) post.
3) 12AWG ground wire from ACR ground tab to chassis ground. The seatbelt bolt closest to the ACR makes a great ground point (1/2" ring terminal). This ground wire is only used to trigger the relay, so it does not have to be the same size as the power wires to the ACR. Blue Sea Systems recommends installing an inline fuse on this wire.
Install a fuse or circuit breaker on the wire going from the ACR to the auxiliary battery as close as possible to the positive post of the auxiliary battery. 60A should be good for 8AWG wire, 80A for 6AWG. Do not install the fuse until all other connections have been made.
Ground the auxiliary battery using the same gauge wire that you used for your positive wire. Once again, the seat belt bolt closest to the battery is an ideal ground point (1/2" ring terminal).
Wiring Acessories to the Auxiliary Battery:
With the auxiliary battery connected to the van’s charging system, the best way to distribute power to the accessories that you want to run from the auxiliary battery is to connect a multi-circuit fuse block. The Blue Sea Systems 5029 (12 Circuit) or 5028 (6 Circuit) fuse blocks are a great choice since they are well built and use readily available ATO automotive blade style fuses. Since the chassis of the van acts as a common ground point, there is no need to purchase a fuse block with a negative ground bus.
Connect the fuse block to the positive post of the auxiliary battery with 8AWG (or larger) wire. Install an inline fuse (60A for 8AWG wire, 80A for 6AWG) as close to the positive battery post as possible to protect the wire. Most batteries with bolt style terminals use a 5/16“ ring terminal and the fuse block will use a 1/4" ring terminal.
Run an appropriately sized wire from the fuse block to each accessory (light, fan, refrigerator etc) you would like to power from the fuse block. You can determine the proper wire size based on the amperage or the wattage that the accessory draws. If only wattage is listed, divide watts by volts to find amps. Once you know the maximum amperage the wire will be carrying, use an online ampacity chart to select the right wire gauge. If you are near the limit of a wire’s maximum capacity always choose the next larger wire size available. Be sure to install a fuse sized at or below the maximum ampacity rating of the wire into the fuse block to protect each accessory.