Rear Dual Battery Cable Length

[Spilsy Avid PP Poster! Find all posts View Profile Close Spilsy]

Can anyone give me some advice on how many metres of cable would be required to set up a dual battery system as follows:

• 2nd Battery in the rear cargo area
• VSR/Isolator in the engine bay
• Anderson Plug break in the system (Allowing for battery portability)
• Earthing of the system at the rear of the Vehicle (a location would be appreciated)

I don't want to buy excessively more cable than is required. I am looking at full dual battery kits, which generally offer either 4 or 6 metres of Red 6B&S, and about 0.5m of a lesser black cable.

It seems cheaper to buy the kit than to buy the items individually.

[Guest Close Guest]

I used 3m to get to the 2nd row footwell on the passenger side i.e. the cable length stayed on the same side of the Prado.

For your situation, go with 6m, or at least 5m. 4m is too exact.

Run twin core so the earth is back to the starter battery.

[Spilsy Avid PP Poster! Find all posts View Profile Close Spilsy]

For your situation, go with 6m, or at least 5m. 4m is too exact.

Run twin core so the earth is back to the starter battery.

I reckon I could open a huge can of worms with this question, and I'm sure if I trawled the Dual Battery guide there'd be an explanation, but, to quote a viral video that I'm sure everyone has seen, "ain't nobody got time for that":

Why earth back to the starter battery? Surely earthing to the body or chassis close to the 2nd battery is a smarter option? Perhaps its too hard to find a suitable earth point?

[ravenhard Member Find all posts View Profile Close ravenhard]

Having recently done a dual battery install, it all ready depends on where you are mounting the vsr in the engine bay and where the second battery is in the cargo area. I used 5m to go from driver side battery to rear passenger side just behind second row seat Then another 2m from that to the rear tow bar for the Anderson.

I got 8m as that was what was available eBay at the time for a decent price

Oh and on the other topic I always run 2core twin sheath 6b&s cable. Less voltage drop then depending on the body for a decent earth

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

There's a few reasons not to use the body as a return, a panel might
look well earthed and test ok, you try to draw a lot of current like
running an inverter and you find your brake line melts etc.

Today cars are more or less glued together and your relying on spot welds to carry
the current. Also using body return can introduce earth loops and you find things like
radiators corroding due to stray currents.

Safer to run an earth return, even the manufactures run an earth loom and they wouldn't
if they thought it was safe to use the body as an earth return.

[Spilsy Avid PP Poster! Find all posts View Profile Close Spilsy]

I want to go from the starter battery, passenger side, to my 2nd battery, about 200 mm behind the 2nd row on the drivers side. I want to break the line with an Anderson plug as close to the battery as possible (say within 300 mm). It doesn't concern me which side everything runs, as long as it comes out in the cargo area (for simplicity sake, I'm thinking that I'd run everything down the passenger side, and come up, if possible, just behind the 2nd row seats.)

Also, looking at various wiring diagrams, I am seeing that there are fuses on either side of the VSR, or either side of an Anderson plug. Is this necessary?

[Guest Close Guest]

Fuses are required at the end closest to any power source. For very short runs, it is debatable whether fuses are required. It is basically to prevent short circuits. Over a long run, there is a higher chance of a cable being cut somewhere along the line.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

I did something similar. Ran 6B&S from the starter battery (+ve and -ve) through a manual circuit breaker (allows me to trip the supply like a switch if necessary) through the grommet on the passenger side, down along the tray under the scuff panels and into the back. Took the rear seats out and put a battery box on a board. The power cable terminates in an Anderson plug that then plugs into the feed to the DCDC charger on the battery box. The feed goes into a changeover relay so I can connect solar in when camping. I unplug the supply when I take the battery box and board out to refit the rear seats. The feed from the changeover relay isn't fused to the input of the DCDC charger. Output from the DCDC charger to the auxiliary battery is fused as are the take offs. Some pics in my build which is linked from my signature. Have done a similar thing in the utes but as they don't have the battery box in all the time I set that up with an SBi12. Again with a manual circuit breaker to trip the cable when not in use.

I used Redarc products and wired them as per Redarc's recommendations on their website.

[Spilsy Avid PP Poster! Find all posts View Profile Close Spilsy]

I did something similar. Ran 6B&S from the starter battery (+ve and -ve) through a manual circuit breaker (allows me to trip the supply like a switch if necessary) through the grommet on the passenger side, down along the tray under the scuff panels and into the back. Took the rear seats out and put a battery box on a board. The power cable terminates in an Anderson plug that then plugs into the feed to the DCDC charger on the battery box. The feed goes into a changeover relay so I can connect solar in when camping. I unplug the supply when I take the battery box and board out to refit the rear seats. The feed from the changeover relay isn't fused to the input of the DCDC charger. Output from the DCDC charger to the auxiliary battery is fused as are the take offs. Some pics in my build which is linked from my signature. Have done a similar thing in the utes but as they don't have the battery box in all the time I set that up with an SBi12. Again with a manual circuit breaker to trip the cable when not in use.

I used Redarc products and wired them as per Redarc's recommendations on their website.

I took a bit of a look at your build thread. I'm thinking that it may be something I refer back to when I get a chance to do all the vehicle wiring.

[Spilsy Avid PP Poster! Find all posts View Profile Close Spilsy]

So - I think I know where I am heading when I come to set up my dual battery system - thanks for the advice.
My next query - if you had to choose, which would take more prioirty - A good 240Volt charger, or my dual battery system.

I am searching for an answer considering the following -

• I'm on a budget - of about $200/month for the next few months - this month's budget was blown on the fridge and battery.
• In the next few months, I plan to go for a weekend camp with the missus (1 or 2 nights), a 4wd trip with some work mates (1 or 2 nights) and a day trip with a fridge load of food for an Easter gathering.
• There is plenty of time between trips
• I also want to buy a battery box (~$70 from next months budget)

My first thought is...get the 240 volt charger first. Charge the battery before trips and it should last (crosses fingers) for the weekends away.

[Guest Close Guest]

depending on ambient temps, the battery (120/130Ah) will probably last. But what you don't want to do is run it completely flat. For battery longevity, you should run it to 50% SOC (State Of Charge).

[Spilsy Avid PP Poster! Find all posts View Profile Close Spilsy]

But what you don't want to do is run it completely flat. For battery longevity, you should run it to 50% SOC (State Of Charge).

Hmmm...thats definitely something I have over looked. I have access to a charger (possibly via the system in mum and dads caravan) so it may be best to focus on the dual battery set-up in the first instance?

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

If you are on a tight budget then use the battery charger that comes supplied with your vehicle, your alternator, to get you through in the short term!

I often see people going to no end of trouble and expense to optimise their setup so they can stay just that little bit longer without starting the car. Running the engine at idle for half an hour will probably cost you under a dollar in fuel.

Does your fridge have a low voltage cutout? If it does then set that to the highest voltage cutout and you should have no worries about flattening your battery, if the fridge isn't running then its time to start the car and charge the battery a bit.

You can also crib a bit by running the fridge a bit colder until you stop, say -3 or so, then put it up to +3 when you stop, meaning it will run less. If you have space you could also freeze a 2 litre milk bottle of water and whack that in the fridge to help lower the power consumption of your fridge.

There are lots of options for shorter trips if the coin is tight for the upgrades you ultimately want.

As for battery chargers, I still use a cheap 4 amp battery charger that Noah threw off the Ark, it will still top up a battery if you have the time to leave it hooked up.

Cheers Andrew

[Spilsy Avid PP Poster! Find all posts View Profile Close Spilsy]

I like the use of the kiss principle AJ.
I have no objection running the car for a bit at all. It's just connecting the aux battery to the alternator. I can I think get all the dual battery stuff for about $150. I'll link all the bits when I have my pc in front of me.

[Spilsy Avid PP Poster! Find all posts View Profile Close Spilsy]

My List of Bits: Have I missed anything?

6m 6 B&S Twin Core Cable
Narva VSR
Various Lugs
50 Amp Circuit Breaker
Anderson Plugs