Thread: Anderson plug additon to D90 - (con)fused

Hi Nick, all you need to do is fit a 50 amp AUTO RESETTING CIRCUIT BREAKER in the positive cable coming from the battery's positive ( + ) terminal.

You can still jump start through the circuit breaker before it trips.

Originally Posted by drivesafe

Hi Nick, all you need to do is fit a 50 amp AUTO RESETTING CIRCUIT BREAKER in the positive cable coming from the battery's positive ( + ) terminal.

You can still jump start through the circuit breaker before it trips.

Thanks drivesafe! I'm a bit of a noob to this, so excuse the very basic questions. Out of interest, what would you recommend as the best nearby earth point for the (-)ve cable?

Hi enchappo, welcome to the forum. There is no such thing as a stupid question. We all had to start somewhere. The beauty of this group is that there are a lot like you, just starting out and there is a wealth of knowledge to be found here. Jim

I used the Blue sea Systems 187 series circuit breakers in my Ex Box build (Thread >>HERE<<).

These circuit breakers have a delayed trip function, as seen in the Trip delay curve below


Product page here

For the earth point, given what you've specified your location to be, I'd be going along the lines of the anderson connection mounted to the front of the box going to a cable gland to go thru the battery box into the battery compartment. From there, simply run your positive cable to the output side of the circuit breaker, then onto the positive lead of the battery, and connect the negative lead of the anderson plug wiring direct to the earth post of the battery.

If your defender is anythign like my 2012, the negative battery lead uses a stupid conical nut arrangement to tighten the cable to the earth post. If you have the tools, or are able to get this changed over to a terminal with provision for mounting a ring or lug terminal, your future electrical mods will be easier.


When fusing, you want the fuse to be as close to the positive side of the battery as possible, and of a suitable rating to prevent it tripping/ blowing given the amperage the circuit is likely to draw.
Most components of quality specify what current they are rated to for a given time period (sometimes 100% duty, intermittant (~5min), and <5seconds, so always keep this in mind when selecting what components you are using. Also keep in mind cable size needs to be able to handle the current of the system also. Realistically, 16mm2 cable may fall short for high amperage draw for long periods of time (say cranking over a stranded vehicle for a long time (>30s). I'd be pushing for 25mm2 or maybe 35mm2, depending on what your usage is likely to be.

Originally Posted by jx2mad

Hi enchappo, welcome to the forum. There is no such thing as a stupid question. We all had to start somewhere. The beauty of this group is that there are a lot like you, just starting out and there is a wealth of knowledge to be found here. Jim

Thanks Jimbo. Have been lurking for a while, and have been super impressed with the wealth of information and the willingness of people to give their advice.

Hi Mitch and all AUTOMOTIVE type circuit breakers ( and fuses ) operate in the same way as shown in your chart.

That shows why you can jump start through a circuit breaker and not trip it.

BTW, the current carrying capacity of an Anderson plug is also similar to that charts current base.

Originally Posted by Toxic_Avenger

I used the Blue sea Systems 187 series circuit breakers in my Ex Box build (Thread >>HERE<<).

These circuit breakers have a delayed trip function, as seen in the Trip delay curve below
[image removed]

Product page here

For the earth point, given what you've specified your location to be, I'd be going along the lines of the anderson connection mounted to the front of the box going to a cable gland to go thru the battery box into the battery compartment. From there, simply run your positive cable to the output side of the circuit breaker, then onto the positive lead of the battery, and connect the negative lead of the anderson plug wiring direct to the earth post of the battery.

If your defender is anythign like my 2012, the negative battery lead uses a stupid conical nut arrangement to tighten the cable to the earth post. If you have the tools, or are able to get this changed over to a terminal with provision for mounting a ring or lug terminal, your future electrical mods will be easier.


When fusing, you want the fuse to be as close to the positive side of the battery as possible, and of a suitable rating to prevent it tripping/ blowing given the amperage the circuit is likely to draw.
Most components of quality specify what current they are rated to for a given time period (sometimes 100% duty, intermittant (~5min), and <5seconds, so always keep this in mind when selecting what components you are using. Also keep in mind cable size needs to be able to handle the current of the system also. Realistically, 16mm2 cable may fall short for high amperage draw for long periods of time (say cranking over a stranded vehicle for a long time (>30s). I'd be pushing for 25mm2 or maybe 35mm2, depending on what your usage is likely to be.

Thanks Mitch! Don't worry? I've been following your build thread for a while now with interest (and some envy). The extras you are installing are pretty much exactly what I want to add to mine, although I've decided to go with portable rather than on-board air? AND I don't have the electrical or fabrication skills to do the personal tweaks you are adding . I'm planning to talk to Daniel once he is back from holidays about getting an ExBox (plus a Frontrunner rack, APT steering guard, nugget sealed airbox and breather kit? looks like an expensive visit for me)

And thanks for the really helpful post. I did think about whether 16mm2 would be enough, but then I saw an Anderson reseller say that 16mm2 is the largest cable size that fits the 50A plug. I also had a question about connecting directly to the negative pole of the battery: I was scared off doing that by posts on here and other forums that said this is a big no-no on newer vehicles. Thoughts?

Originally Posted by drivesafe

Hi Mitch and all AUTOMOTIVE type circuit breakers ( and fuses ) operate in the same way as shown in your chart.

That shows why you can jump start through a circuit breaker and not trip it.

BTW, the current carrying capacity of an Anderson plug is also similar to that charts current base.

Drivesafe, so something like this is adequate? It's what I was planning on using based on your earlier post.

I don't profess to be an electrical engineer (just a garage hack, actually), but thanks for pointing out the similar characteristics of other components.

I guess it all comes down to what amp draw an 'average' starter motor draws? Or if we are wheeling with others, what their starting amperage might be . 600CCA batteries are normal, however their hot cranking amps are much higher. How much of this available current the starter motor needs in a jump start scenario is the real question.

In other applications they talk about an Imax and Ieff value, ie starting current draw and efficiency 'stabilized' current draw. Welders for example can draw 18A on startup, then they 'settle' to a 15A draw.
The conundrum becomes whether we select a fuse for the spike, or the plateau? And how large the spike is relative the the efficiency rating, as this could have a large impact on how the circuit will handle the load, assuming all other components can safely handle it.