Tripple Batt Setup

Thanks Sand Man i was hoping for a positive first reply,

What size fuse and make do you recommend i was thinking of connecting the 3rd battery directly to the Aux battery stud on the isolator.

Regards

Stephen

Stephen,

It depends on what you intend running from your "distribution panel" but 10 amp should be adequate.

You can buy an "in-line" blade fuse holder from Repco, or the like, then the fuse will be the same as you use elsewhere in the vehicle circuits.

The auxiliary battery terminals is the best place to connect your wiring and I recommend you run a twin core cable so that the return wire is back direct to the battery, rather than rely on the vehicle's body earth.

Especially important for some "temperamental" fridges.
(brand name withheld)

One very important thing to remember is that you will need two fuses, one at either end of the cable connecting the batteries together. There is no point just having it at one end if it is shorting out in the middle of the line, as the other battery will keep supplying power to the cable. You don't want a fire in the middle of nowhere!

Probably the best thing to use is not a fuse, but an auto-reset circuit-breaker. That way if your out bush, and the cable shorts out, you dont have to worry about fuses.
Check out Derek's site for some breakers http://www.sidewinder.com.au/page27.html

Hmmm,

Other battery???

If you connect the positive wire to the auxiliary battery and fuse it as close as practical to the battery, you are providing protection to the whole circuit.

As far as the remote end is concerned, the fridge, or its supply lead has its own fuse to protect it, but in any case, not really required.
If the "master fuse" is protecting the supply source, that's all you really need.

N0, the whole circuit will N0T be 'protected'
Protection will only be available from the front Aux battery - not the rear battery.

Because; 12v power runs in the (+) battery cable in both directions, the Aux battery in the Camper will also be supplying 12v power to the (+) cable.

Therefore 12v power will be available from BOTH batteries at the point of separation or "short" not just from the first battery, hence the two (2) fuses are required as close to each battery as practicable and in a 'short' BOTH will blow.

Remedy, fix the problem that caused the 'short', replace both blown fuses and all will be fine.

"Remedy, fix the problem that caused the 'short', replace both blown fuses and all will be fine."

Or use auto-reset circuit breakers, then you will not have to worry about carrying spare fuses

Maybe I should have typed-> "Remedy, fix the problem that caused the 'short' and then all will be fine"

Even with "auto-reset circuit breakers" you have to fix the problem first, before the auto reset circuit breakers will reconnect the power again.

How often have you blown a "fuse" in a 12v dual battery system cable between the two 12v batteries ?

A fuse between 2 x batteries is only required when you are likely to have battery cable shorting problems, if you first consider what causes these problems during the cable installation they can then be avoided by correct electrical installation techniques.

I don't use a fuse in my own dual (triple) battery system and Mr Toyota did not use a fuse in his battery cable either.
All the accessories are fused in their independent power cables.


HOWEVER:
that said, I always recommend a 'Fuse' (or 'circuit breaker' or whatever device is believed to be superior to a fuse) in the (+) battery cable @ all the battery (+) terminals, running to/from a Camper trailer or Caravan.