Electrical Cable Management for Dual Battery Systems

[tolyinoz Lurker Find all posts View Profile Close tolyinoz]

Hi Everyone,
I've finally bought my first 4WD and after reading this wonderful forum I'm very keen to start my mods.
I've bought a used 2011, 150 series Prado which already came with a Piranha DBE 180s Dual Battery Management System. The wiring looks a little messy with 3 separate wires running to the auxillary battery's positive terminal. Would it be better to run a main wire to a fuse box and branch out from there? I also have a separate cable running to the towbar with an Anderson plug on it, presumeably to charge a trailer or caravan battery. It's connected to the main battery, would it be better running it to the auxillary battery instead?
I'd love to hear your advise and I'd love to see your pics of your cable management.

[Geoffury Find all posts View Profile Close Geoffury]

Have a look in the electrical section of the 150 part of the forum, there's numerous threads there to get info from. Also look at the rig build ups in the general section of the forum.

[tolyinoz Lurker Find all posts View Profile Close tolyinoz]

Hi Geoff,
Thanks for the reply. I've been reading the posts; thought it might be nice to start a cable management thread.

[zzsstt Junior Member Find all posts View Profile Close zzsstt]

Cable management comes down to personal choice, but with a few rules.

Fuses are to protect the cable, not whatever is on the cable. So each cable must have a fuse, as close as possible to the start of the cable, that is rated at less than the ampacity of the cable though this does not preclude using a much smaller fuse if desired. Cables must be rated sufficiently to carry the intended load, at an acceptable level of voltage drop. Then, obviously, cables must be suitable for the purpose (some domestic wiring cables are not oil-proof and the insulation can soften) and protected from physical damage.

So ideally a large cable that feeds a distribution box should have its own fuse at (or very close to) the battery. Each cable leaving the distribution box should have its own fuse, which is rated at the lower of either the maximum capacity of that cable or the requirement of the connected device. The total load on the distribution box must be below the capacity of the cable feeding that box. And all cables runs, in total length from the battery to the device, must give an acceptable voltage drop when they are simultaneously at full load.

One of the reasons that people use multiple individual cables rather than a distribution box, is that things tend to be added one at a time and by the time a need is seen for a distribution system it is simply too much effort to retrofit one! Also, of course, the more complicated the system (multiple individual cables looks messy but are very "simple") the more connections exist, the higher the chance of problems taking out multiple systems, and the more fault finding is required!

I tend to use one large circuit breaker next to the battery (to avoid hanging lots of wires off the battery terminal) and then run individually fused cables from there. Even if cables run parallel (like electric brake, trailer power and fridge power all running from to back) I would run individual cables.

Your trailer power cable was probably designed to connect to another battery on the trailer. It probably had it's own charge controller in the trailer, and therefore was connected to the main battery. You will need to decide what you are going to use it for before you know where best to connect it!

[tolyinoz Lurker Find all posts View Profile Close tolyinoz]

Hi Zzsstt,
Thats perfect, exactly what I wanted to know!
It makes sense about upgrading at different stages, therefore not knowing how many leads you will end up with.
I'm still fresh so don't mind tackling a re-wiring job.