Auxiliary Fuse Box?

Mac90 said:

Hi there,

I'm looking for a little bit of advice regarding installing an AUX fuse box. The 1996 300tdi 100 csw that I have recently purchased has a raptor dash with no less than 14 ports/switches!Only three of them are connected at the minute, drawing from existing ignition activated 12v feeds.I have plans to use some of the other ports/switches, for various applications that I won’t bore you with.

My thoughts are that it would be simpler, safer, and more reliable to install a new auxiliary fuse box rather than continually look for power feeds, and perhaps overload the small factory fitted fuse panel, when I want to install a new device.

I want to do it myself, and I have a little bit of experience with wiring, soldering etc but by no means an expert!Has anyone done the same or similar in the past?

Here is my outline so far, I’d appreciate any feedback on anything that isn’t safe or appropriate!

1.Mount the 100 amp total rating AUX fuse box perhaps in the Raptor glove boxto the left of the switch panel for easy access.





2.Mount a 100A breaker in the seat box.



3.Run a positive and a negative feed of 16mm² 110 Amp cable direct from the battery (perhaps a second leisure battery in the future) to the breaker.

4.Continue the positive and negative feed from the breaker to the AUX fuse box with 6mm² 50 Amp cable.

5.Use 2mm² cable to wire positive and negative feeds to the carling switches from the appropriate terminals of the AUX fuse panel.

6.Install the appropriate fuse for the application running from the carling switch.For example GPS charger: 5 amp.

Am I missing anything or doing anything wrong with this plan?

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mick 1986 said:

There are several ways of wiring it in, but protecting 6mm (50A) cable with a 100A breaker is nuts. It’s asking for a fire! The circuit breaker/fuse is only there to protect the cable.

Either run the 16mm cable direct from battery to circuit breaker/fuse, and all the way to the fuse box, or reduce the circuit breaker value to 50A.

I will have 2 batteries, and 2 fuse boxes, wired in my battery box. It will all be connected with 16mm cable and 100A fuses. I had this setup before the rebuild, in a different seat box, and will be going back to it.

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Mac90 said:

Thanks for the input Mick! Therein lies my inexperience!

So I'm understanding correctly, it's ok to run 16mm² 110amp cable direct from the battery to the breaker, and then continue on with the same cable to the AUX fuse box? If this is the case then the breaker that you are suggesting should be 50A or 100A?

I'd rather have the setup be more than capable than just enough, if you know what I mean!?!

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mick 1986 said:

The breaker is to protect the cable, so if you use 100A breaker, you need 16mm cable, from battery to fuse box.

If you run 6mm cable from battery to fuse box, then 50A breaker. This would be my choice for a single battery install, but with a 40A breaker instead of the 50A.

What is the output of your alternator? You may find that installing 100A of extra capacity, while only having a 63A alternator, will continuously flatten the battery.

The only reason I went so high on my install is because it’s all from the second battery. If I flatten it while camping, or fishing/hunting, then I can charge it at home when I return. Don’t overspec the current and the alternator will keep the battery topped up.

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Mac90 said:

Thanks for the continuing advice Mick!

I'm pretty sure I'm on the standard alternator at the moment, although I thought that was 65 amp? Possibly going to upgrade to 100 amp soon (https://www.island-4x4.co.uk/alternator-high-output-britpart-amr5425-yle10113-amr4248-p-3995.html) however, and / or install a second battery.

I wasn't planning on getting to close to the 100A capacity of the additional fuse box, as it will be mainly for LED lighting and charging ports etc. So nothing that has a high load. Just wanted to future proof it really.

So the choice is 6mm² from the battery, through a 40A breaker, then into the fuse panel. Or, install a second 100 ampH battery with a split charge management system, and then use higher rated cable for that?

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mick 1986 said:

That’s the two ways I would do it. Either will work, but if it’s just for LEDs and 12v charging, go with the 40A setup. The cable alone will be around 1/2 the price, and it saves on the additional costs of upgrading the alternator or a second battery. Both upgrades could be done in the future, and your system could then be upgraded or moved over to the second battery.

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