My Dual Battery Install

[ova50]

2010 DX 3.0 litre.

I started by putting pen to paper, listed the accessories I use and take when we travel, and what amps they draw, and how many of the items I am likely to use at the same time. I decided on 5 accessory plugs in the vehicle plus an Anderson Plug for the caravan.

Accessories: Winch, UHF, Elect brake controller, Scan Gauge, Fridge, GPS, Car Cam, A selection of various charging equipment for phones, computers , E book, still cameras, video camera, and power to the C-tek dual charger in the caravan. (van also has solar)

Main Parts I used: ARB battery tray. Redarc SBI 12. Supercharge Allrounder battery MRV70L . 2 x 100 amp circuit breakers. Fuse holders. Accessory sockets. Anderson plug. Wire: 4 gauge (135amps), 8 gauge (55 amp), and twin 15amp rated wire for the sockets. Volt meter, 3 position switch, various terminals, heat shrink, 90deg brackets. Cable conduit. Bolts etc. And a box of band aids.

First was where to mount sockets, Uhf , fuse box etc in the cabin. Once done, I decided to start from the rear and work forward.
Removed trim panels etc on the passengers side fitted the Anderson Plug and run the 8g wire from the Anderson up through the floor behind the panel using wiring grommets , and to the front floor. Also fitted the rear socket and run the wires (15amp) along the same route. (wire was 6 metre lengths) Fitted 2 sockets into the rear of the consul and run the wires under the consul. Removed the glove box and drilled two holes into the white plastic mounts near the heater fan, fitted 2 small brackets and mounted the Uhf (Oricom 80channel) then mounted the Uhf head unit to the console, fitted a twin socket on the top of the foot air vents (this socket is for the GPS & Car Cam.) Fitted the Fusebox. Fitted the Volt meter, and a 3 position switch in the consul, I also fitted a 5ag fuse holder into the front side of the console.

I decided to run the 8 gauge cable through the side left side panel ( behind the kick panel ). Removed the plastic inner guard. Drilled the holes and run the cable through and back up into the engine bay ( I used wiring grommets and also ran the cables through conduit, also ran the uhf antenna lead this way).

The volt meter & 3 way switch. I wanted to be able to check voltage at either battery using one gauge. Fitting the 3 way switch (on/off/on) and reverse wiring it gave me the result. The volt meter I used was the smallest I could find, and is a 3 wire connection.

The 5ag fuse holder. I decided to fit this so I can disconnect the power to the Anderson Plug if I am not towing. Only have to pull the fuse out.
Next step was the engine bay.

Battery Tray: The mounting holes on the ARB tray seemed to be a couple of mm out, I had to drill all the holes a little larger so I could get the bolts to line up on the vehicle & fitted the battery. (using stainless terminals)

Next steps: Removed the intercooler shroud, disconnected the winch wires from the main battery and re-routed them over to the Aux Battery and fed them through conduit. Fitted both the 100amp circuit breakers using some brackets and fitted the Redarc. Fitted a 4g cable from main battery and circuit breaker along the firewall, using “P” clips and conduit. Connected the “Smart Start” using a momentary switch. Connected 4g cable from the Redarc to the other circuit breaker and then to the aux battery. Fitted an inline 5ag fuse holder to the 8g accessory cable and connected to the aux battery. I also fitted a suppressor to this cable. Ran a 4g earth wire from the main battery to the aux battery.

Almost done: Used a volt meter to check engine bay wiring, circuit breakers and Redarc. Inside the vehicle connected all wires to the fuse box and checked all points with the voltmeter. Switched ignition on and checked voltage of both batteries with the 3 way switch. Checked the “Smart Start” momentary switch, heard the Redarc click. All good. Started the vehicle and the volt meter & switch does the job and the Redarc operates fine.
Job done.
I used as many existing studs or bolt holes to mount the brackets & cables to. Have used nylock nuts where possible, heaps of conduit, all lug connections were crimped and used heat shrink. Used 7 band aids.

Hope you guys don’t bag me out too much if I have it wrong. (Im still learning)

DBT
The Pics ( having problems uploading them in order)

[MudRunnerTD]

Looks like you did a great job. Good write up. Thanks for taking the time to document it. I have quite a few projects that I have done and have the pics but not got around to doing the write up.

Another good thread for our Brain Trust.

Cheers MR

[threedogs]

No more to say great write up, great pics, well done great work

[Cuppa]

Yes a very neat & well documented installation.

It does raise a question for me however, a genuine question, so please do not think I am making any criticism of your installation.

It’s about the purpose of having dual batteries for use when winching. Why is a dual battery setup preferred over simply having the winch connected to the crank battery?
To answer myself ........ I assumed it was because a winch can use a large amount of current when at ‘full noise, as much as 500amps, & although it is the norm to have the engine running whilst using the winch, that having two (or more) batteries in parallel helped to reduce the impact that a single battery would receive. (Peukerts Law). (The higher the current draw the less capacity is available) Very high currents like this thus being more sustainable with an effectively larger battery capacity. All you blokes well versed in winching ..... is this correct?

I ask because if this is correct then having the 100A circuit breakers between the two batteries would appear to me to prevent the use of the winch running off both batteries except under very light use, when the winch is pulling less than 100amps. I can’t recall how my vehicle’s Telstra dual battery set up with an SBI12 was exactly, but it had no circuit breakers & the winch was connected to the start battery rather than the aux battery.

When I removed the aux battery under the bonnet & replaced it with 3 x 120AH batteries in the pod with the ability to manually connect them to the crank battery when winching, I asked here about using circuit breakers or fuses, because of concern about the risk of fire if the joining cable were ever damaged & shorted against the vehicle. I was told at the time that because of the large currents involved in winching, most folk did not use fuses or circuit breakers in this particular application. However I was not happy to go without such protection, my joining cable is 70mm2 & runs several metres under the vehicle & into the engine bay. With it connected to all 4 batteries the thought of the amount of curent which could be involved if it were ever to short out scared the bejesus out of me, so much so that I went to quite an expense to fit fuses (megafuses) which will allow the winch to be used on ‘full noise’, or close to. They are rated at 450 amps.

[First Patrol]

I can't comprehend the amount of research you have done and knowledge you have on the electrical side of things cuppa!!!!
I love reading your posts!!!!!!!

[Cuppa]

I can't comprehend the amount of research you have done and knowledge you have on the electrical side of things cuppa!!!!
I love reading your posts!!!!!!!

Thanks FP, but I suspect that I am displaying a lack of knowledge on this instance!

[First Patrol]

Thanks FP, but I suspect that I am displaying a lack of knowledge on this instance!

You never know everything mate lol

[First Patrol]

Sorry....... No one knows everything ( not directed at you cuppa)

[Cuppa]

I posed the ‘why’ question on another forum (motorhome) I frequent hoping to get an answer from some friends far more knowledgeable than me, & who have 4wd motorhomes. I trust their expertise.

I wrote
My assumption was that two (or more) batteries were better than one for winching because of the potentially high current draw. My limited understanding of Peukerts Law (a battery has less available energy at high current draw than at low current draw) suggests to me that the reason for paralleling 2 or more batteries, is to increase capacity relative to the current draw, reducing the impact on the batteries by spreading the load across both (or all). By doing so it is less damaging to battery life expectancy as well as providing longer winch time capability (in conjunction with motor running/alternator charging of course).

My assumption was confirmed as being correct, & in addition "and its also about power. Less voltage drop with more energy capacity”.

Cuppa

[megatexture]

Love the fuse box i Just put one of these in my camper and love it having the blown fuse indecator LEDs beats testing each one

http://www.jaycar.com.au/productView.asp?ID=SZ2001