Where to Run Battery Cables to Rear

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Chris Skinner
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Where to Run Battery Cables to Rear

Post by Chris Skinner »

I am busy installing a battery in the rear compartment. Was just wondering where best place is to route the cables through to the engine bay. I am planning on using 25mm2 cable which has a double insulation and is quite thick. I will take both + and neg to the front. I have measured the distance and will require just short of 5 meters of cable.
I found that a good place to run the cables is along and under the door sill. In the front driver side I do not find a rubber grommet in the firewall, but there is a drain hole in the floor approximately under the accelerator. Problem with this is - how to seal it again if I run the 2 thick cables through that hole? :think:
Another question I have is whether I will be able to use the second battery in parrallel to the main to add extra amps when winching - will the 25mm2 cable be good enough? :think:
I also intend placing a Circuit Breaker (not fuse) close to the aux battery - was thinking of 150amp - ?? :think:
I also plan to install a CTEK 250 Dual DC-DC charger in the rear, which can also take a solar panel input.
Any comments or suggestions from you guys out there?
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Tinus lotz
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Re: Where to Run Battery Cables to Rear

Post by Tinus lotz »

25mm cable is good for 125a to small for the winch especially at 5m you need at least 35 or 50 would be better . Run it next to chassis in sprec and keep away from carpets hot carpets makes fire....you need a big KA breaker and that will be very big in size biggest single pole avalible is a 125a the dont like sand and dust .still think a big switch or soliniod will be the answer I will get you s 315 fuse .remember breakers font allow for start up preak amps it trips .
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Chris Skinner
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Re: Where to Run Battery Cables to Rear

Post by Chris Skinner »

Right Tinus, however, I will definately not use the rear battery alone to power the winch. It will always be in parrallel to the main battery and with engine running. I therefore dont think it will ever pull more than around 100amp from the rear, but would like to test that theory if I can find a suitable amp meter. Same for starting, if main is too weak to start engine, the wires from the rear battery is basically same as a jump cable., and this 25mm2 looks more capable than the average jump lead.

I have done some interesting tests – “… om the meet is om te weet...! ” :eureka:

I have tested this by shutting off fuel pump and then run the starter through the 5m cable for approx 20 seconds (in cycles of 5 second on 5 seconds off – this more than enough – my 4,8 always starts in a split second anyway), and there is no noticeable temp rise on the cable at all.

I have done a similar test with the winch. Both batteries connected and run the winch under heavy load for approx same time it takes to load by boat – again, no perceptible rise in temp in the wire.
The reason why I was thinking of using the second battery in parallel is that after a couple of days winching the boat onto the trailer, the main battery losses most of its capacity as my vehicle and boat stay on the beach and I do not drive around enough to recharge the battery and there is no external power available – my thinking is that the battery power will last twice as long by using 2 batteries, and seeing I have a second battery, why not use it in this way.

I was also re-thinking the routing of the wiring – best is to go through the firewall I think, than through the floor (water leaks etc), but I will have to find a way to make a new hole in fire wall and use a suitable grommet – any ideas there?

I have another idea which I want to try as well - is to place a relay (one from my old winch control box) in the +pos line of the second battery. The re;ay will be activated by the starter motor relay and the winch relay - in this way the second battery will always be isolated unless starting the car or running the winch. Of course this set-up will only be used when I am in the boating mode.... :eureka: :eureka: :thumbup: :thumbup:

If anyone thinks my ideas are suspect please advise or add your comments....
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Tinus lotz
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Re: Where to Run Battery Cables to Rear

Post by Tinus lotz »

I have a suitable clamp meter that you can use come around tommorow and we can make a plan the winch realy will work 100.%
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Re: Where to Run Battery Cables to Rear

Post by slmr »

I ran mine thru the chassis- 25MM2 + in plastic pipe & earth free (no pipe)- works fine
Only need to protect the +ve against chafing
Don't run a winch, but calcs say you should not be pulling >125A sustained...think you will be ok
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