This article documents my installation of a simple split charge system into my series III Land Rover. It has been installed as I use the vehicle for camping and need to run lights and radios for extended periods. This system will prevent the starting battery being drained.
Items I bought
The Goodies
Before I started the installation I drew up a simple wiring diagram so I had something to work off. This should be pretty generic and will work with most setups
Wiring Diagram
The Relay I used is only rated to 100amps, but seeing as my alternator is only 65 amp its not really a big problem, although I may up rate this to 100amp at a later date to help charge the batteries easier.
The relay is wired up like this
Spare Terminal
I used two cables for the fuse box lives, using each cable to supply three separate auxiliary feeds. The cable is rated at 30amps which means I can split 30amp over both feeds. For example I can have two 5amp fuses and a 20amp, and then on the other side I can have three 10amp fuses without over loading the wiring.
Aux fuse box and heavy duty 100amp Relay
After some quick testing I found I needed to tighten the fan belt as the extra load charging both batteries placed on the alternator made it squeal a little. After a tweak all was well and both batteries charge at 14V at tick over.
I intend to put a switch between the ignition feed and the relay so i can manually disconnect the aux battery in case there is a fault or the alternator is not charging correctly.
This is the completed setup with a single feed being used from the fuse box for my radio, I will be adding more accessories in the near future. The batteries and relay are housed in a locked MOD jerry can locker behind the passenger door.
Finished battery box
Items I bought
- Cable 126/0.40 - 1 Metre (Linking batteries to Relay)
- Cable 28/0.30 - 5 Metres (Relay Trigger and Earth)
- Heavy Duty Relay 12v 100Amp
- Surface Mount Fuse Box - 6 way
- Sundries (terminals and solder)
The Goodies
Before I started the installation I drew up a simple wiring diagram so I had something to work off. This should be pretty generic and will work with most setups
Wiring Diagram
The Relay I used is only rated to 100amps, but seeing as my alternator is only 65 amp its not really a big problem, although I may up rate this to 100amp at a later date to help charge the batteries easier.
The relay is wired up like this
- Pin 30 - Main Battery Positive
- Pin 87 - Aux Battery Positive
- Pin 85 - Ignition Live
- Pin 85 - Earth
Spare Terminal
I used two cables for the fuse box lives, using each cable to supply three separate auxiliary feeds. The cable is rated at 30amps which means I can split 30amp over both feeds. For example I can have two 5amp fuses and a 20amp, and then on the other side I can have three 10amp fuses without over loading the wiring.
Aux fuse box and heavy duty 100amp Relay
After some quick testing I found I needed to tighten the fan belt as the extra load charging both batteries placed on the alternator made it squeal a little. After a tweak all was well and both batteries charge at 14V at tick over.
I intend to put a switch between the ignition feed and the relay so i can manually disconnect the aux battery in case there is a fault or the alternator is not charging correctly.
This is the completed setup with a single feed being used from the fuse box for my radio, I will be adding more accessories in the near future. The batteries and relay are housed in a locked MOD jerry can locker behind the passenger door.
Finished battery box
