Thread: Defender TD5 dual battery installations

Hi uhuforrest, you have already got your set up running so I’m not trying to sell you one of mine, it just that as you have a limited space, as with all the fenders, Redarcs and pirahana, TJM, ARB and the rest are really no more than a fancy solenoid that many people simply connect to the ignition.

They all cut in once the vehicle voltage is up to where it is charging but they also cut out almost as soon as the ignition is turned off.

The point I am getting at is that the main battery has heaps of power that could be used to dramatically extend the operating time of your auxiliary battery while still leaving the main battery with enough to start the vehicle a number of times.

If you have enough stored capacity in your auxiliary battery then they work a treat.

Also and correct me if I'm wrong, but I believe your unit is rated a 100 amps and if so this is way to small the use it for bridging batteries to start vehicles. This is why Battery Switches start at 250 amps and go up and TJM and ARB are rated at 250 amps.

Anyway thanks for the reply.

Cheers.

Hi uhuforrest, starting off two fully charged batteries is fine because you are shearing the load and only about half the current is coming through the isolator, but the problem with having too low a current rated contacts is when you try to start the vehicle when the main battery is flat and you now not only have to supply the starter motor with heaps of current, you will most likely have additional current flowing to the flat battery at the same time and this is why 250 amp contacts are needed.

BTW check and see if the Redarc has a surge current rating for a given time period, if so this may be high enough and long enough to allow you to safely start your vehicle. If there is no surge tolerance, then you are far better off adding a battery switch to cover you if ever you need jump start your vehicle off the second battery.

Cheers.