Dual battery - wiring, fuses and/or circuit breakers

**twr7cx** · 7th April 2011, 04:20 PM

I'm in the process of completing a dual battery set up in my 2003 Land Rover Discovery 2a HSE - the battery tray and battery are in place, but not wired in. I have installed an Optima Yellowtop battery - AGM Deep Cycle Battery, Batteries - Optima Yellow Top - as I want the ability to run the battery down without damaging it. It is my intention to connect the winch to this secondary battery when I fit one.

I am now at the business end of wiring it in.
I have a Matson Low Voltage VSR Parallel Switch - Low Voltage VSR Parallel Switch | Matson - which I will use to control it as I like the automatic feature.

My current issues are:
What size/rating wiring to use?
Where to place the controller - can it be mounted near the second battery or does it have to go near the main battery?
Where to fuse it? What size fuses to use? Should I use fuses or circuit breakers? What size circuit breakers to use?

The Matson unit states: "140 AMP" on it, but the website states:
"250 Amp, 12V continuous. 1000 Amps for 15 seconds. Rated to a maximum 32VDC".
So I don't understand/know what it's actual rating is!?!

I have been reading the Instructions for the Projecta Dual Battery Kits at Projecta and according to that I should:

Be using a 150A fuse or circuit breaker - they recomend the use of the Projecta BT-950-P1 Fused Battery Distribution Terminal ( Projecta ) for this.
Mount the electronic isolator in a convenient location as near to the main battery as possible and no further than 3m.
Be using 14mm2 (6B&S) battery cable.

Can someone please confirm for me that:
14mm2 (6B&S) battery cable is adequate.
What size fuse to use? 150amp is surely to big if the Matson unit is only 140 Amps. Any recomendations on where to purchase fuses of such size from?
The Projecta kit only fuses at the secondary battery positive terminal, surely there is also the requirement for a fuse at the main battery?

**wardy1** · 7th April 2011, 07:45 PM

I'll get in first...... SEND A PM TO DRIVESAFE on here. He knows more about dual battery systems than you need to know and he is a very helpful guy even if you don't buy from him. He is also in the preferred suppiers for AULRO, his business is Traxide Electronics.... he is THE GURU

**Blknight.aus** · 7th April 2011, 08:54 PM

14mm2 should be enough.

I would use a 150Amp fuseable link depending on how much protection you want and if you wanted to retain the the ability to jump start via the unit itself. Dont forget that theres 2 power supplies to the unit one from the main battery and one from the AUX. I find it amusing to see people install $100's worth of DBS and protection on the main battery but then nothing from the AUX battery to the DBS (and in most cases the AUX batteries has the longest run of unprotected cable)

I suspect that the unit itself will deal with 250Amps for an extended period but not forever think along the lines of 140 amps is what it will handle for 15 minutes or so, 250Amps is what it will handle for about a minute and 1000Amps is what it would handle for a second or so. 32V will be the limit of the electronics before it went foom or the non arcing limits in the contact of the relay.

**twr7cx** · 7th April 2011, 09:39 PM

Originally Posted by Blknight.aus

I would use a 150Amp fuseable link depending on how much protection you want and if you wanted to retain the the ability to jump start via the unit itself.

I don't suspect that I will ever use it to jump start via the unit itself, but since that feature is there if possible I would like to maintain it.

**Blknight.aus** · 7th April 2011, 09:45 PM

in that case discard the fuseable links and run the main cable direct.

**twr7cx** · 10th June 2011, 11:42 AM

I have finished the dual battery setup. Custom tray (not made by me), Optima yellow top battery (thats connected to the winch), Matson dual battery controller, with an override switch:

**strangy** · 11th June 2011, 07:43 AM

Are you going to put the turbo heatshield back on? I think it may get a little hot after a while otherwise.

cheers

**def9087** · 11th June 2011, 08:04 AM

Can I ask you where you got the terminal connectors with the two connectors coming off? have been looking for these but can't seem to get them at any shops
thanks

**twr7cx** · 11th June 2011, 08:19 AM

Originally Posted by strangy

Are you going to put the turbo heatshield back on? I think it may get a little hot after a while otherwise.

cheers

Yes, or, soon. The car didn't come with one and I've contact TRS to hopefully source one.

**twr7cx** · 11th June 2011, 08:21 AM

Originally Posted by def9087

Can I ask you where you got the terminal connectors with the two connectors coming off? have been looking for these but can't seem to get them at any shops
thanks

You referring to the battery terminals? They're just Projecta brand ones ( Projecta ) from Repco, had them on my old Falcon and reused them (the battery also comes from my Falcon). They're saddle type, then all I do is instead of using the saddle part I just use the clamp bolts to hold down the cable terminals.

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