Battery cable size for earth?

Submitted: Friday, Aug 28, 2015 at 14:38
ThreadID: 130121 Views:1963 Replies:5 FollowUps:5
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I am designing a future build that will be able to jump start/plus winch assist with the 2 battery's in a ali canopy on a PX Ranger. I will run 00 cable for positive, just wandering if I have to run 00 for the negative earth as well or will 2b&s do as I already have some lying around.
Matt
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Reply By: Member - mechpete - Friday, Aug 28, 2015 at 14:46

Friday, Aug 28, 2015 at 14:46
it would make sense to me to have both battery cables
the same size , otherwise the weakest link in the system would be the smaller earth cable ,
cheers mechpete
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Reply By: Gazza11 - Friday, Aug 28, 2015 at 14:46

Friday, Aug 28, 2015 at 14:46
The Earth return carries the same current as the live side so should be the same size, with a good quality connector with lots of surface area at both ends. If your setup allows both batteries to feed a cct simultaneously then tieing both earths together is also a good idea.

It's good practice to have very heavy cables on both live and earth sides to minimise voltage drop. I'd need to see the schematic of your setup to offer more specific advice but live and earths should have at least 12mm diameter of copper conductor.

BTW never believe the amp rating on jumper leads as they are typically overated by 3 times or more.

Gazza
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Follow Up By: Matthew G3 - Friday, Aug 28, 2015 at 15:26

Friday, Aug 28, 2015 at 15:26
Gazza
I was looking at from the start battery back -250mega fuse -Projecta 200amp VSR with ABR volt/switch link - Blue Sea 250amp terminal feed through -then onto battery`s. Also charge by Redarc 1240lv with 3x80w panels hard mounted. Off the battery`s I would run a Narva 12 way fuse block 30amp circuit 12amp block.
Matt
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Follow Up By: pop2jocem - Friday, Aug 28, 2015 at 17:06

Friday, Aug 28, 2015 at 17:06
What gazza and mechpete said. Have a look at the battery cables to the starter motor. I would be very surprised if both neg and pos are not nice and heavy and the same size.

Cheers
Pop
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Reply By: newwaysys s - Friday, Aug 28, 2015 at 15:31

Friday, Aug 28, 2015 at 15:31
thanks for this informtion
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Follow Up By: TomH - Friday, Aug 28, 2015 at 17:44

Friday, Aug 28, 2015 at 17:44
2 B&S surely would be more than enough. Thats what Landcruisers rune between the linked batteries.

Ive started buses with 4 B&S 5 m long
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Reply By: Slow one - Friday, Aug 28, 2015 at 20:54

Friday, Aug 28, 2015 at 20:54
Matt,
Have a look at how much room there is to run cables that size from your primary battery down and around to your secondary battery, plus the mechanical protection required.

I choose a different way and ran 16 sq mm cable back to my secondary battery via a dc dc charger and on to the rear anderson plug.

If I have to jump start, which I hope I don't have to do. I have a set of jumper leads I made using 50 sq mm welding cable.
AnswerID: 589762

Reply By: Frank P (NSW) - Friday, Aug 28, 2015 at 20:55

Friday, Aug 28, 2015 at 20:55
G'day Matthew G3

I have done exactly the same project in my current model BT50 with a second battery in the canopy.

The cable I have is not marked with gauge, and I cannot recall what I bought. Measuring it up, it is either 0 or 00 - when I calculate the sq mm the result is between the two in Narva's on-line catalogue. Given likely measuring error, I think it is probably 0 gauge, both pos and neg. I ran the neg to the factory chassis earth point near the battery.

I have tested it as both jump start and winch assist and it works fine. It's a long cable run, so IMO it's worth the expense of the heavy cable, especially for sustained loads like winch assist. I used a 300 amp forklift fuse at each end of the positive. Under a heavy winch load I measured a bit under 200 amps in the circuit.

Cheers
FrankP

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AnswerID: 589763

Follow Up By: Frank P (NSW) - Friday, Aug 28, 2015 at 22:41

Friday, Aug 28, 2015 at 22:41
Matt,

Further to the above, just confirming that on a PX Ranger you MUST, absolutely MUST run the negative to a chassis earth and NOT directly to the crank battery negative.

For high currents like you're proposing with winch assist, the recommended chassis connection point is the one on the near side inner guard, near the battery. The factory neg cable between there and the battery is smaller than 0 gauge - may be 2 - but it is a short run so will be ok. No need to upgrade it.

The Mazda is not quite so critical, they do their electrics a bit differently to the Ford, but I chose to do it anyway.

Cheers
FrankP

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Follow Up By: Frank P (NSW) - Friday, Aug 28, 2015 at 23:18

Friday, Aug 28, 2015 at 23:18
And further to my follow-up, Matt, you can get the Ranger's super smart charging system re-programmed to resemble something more normal so that direct connection to the battery negative MAY be ok.

Might be worth browsing a couple of the Ford forums such as this and this.

Cheers
FrankP

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