Dual battery systems

Submitted: Friday, Mar 12, 2010 at 00:12
ThreadID: 76794 Views:4675 Replies:8 FollowUps:4
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I have just put a duel batt system in my Colorado.The Battery wouldn't fit under the bonnet because of ABS . I have mounted the battery in the rear of of the well body , the problem im having is a severe voltage drop beetween the solenoid and the second batt .The cable measures about 6mtrs, Im getting 14.1vlts at the solenoid and only 12.8vlts at the second batt,Ive used the recommended 6ml auto cable and connectors. Any advice appreciated.
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Reply By: Star Bug - Friday, Mar 12, 2010 at 00:29

Friday, Mar 12, 2010 at 00:29
6mm?? diameter of the wire and insulation or 6square mm cross section.
If it's the former then the cable is too small.

You will get some volt drop in any cable though. Especialy if it's drawing high amps.
AnswerID: 408495

Reply By: Mick O - Friday, Mar 12, 2010 at 06:52

Friday, Mar 12, 2010 at 06:52
6mm "Auto" cable is a misnomer. It's got to be a minimum of 6mm squared in copper area. Bigger is better. There are resistance tables somewhere that will tell you the voltage drop expected per 1 metre of cable (Do a google on it). 6 metres is far too long. Can you get the battery up into the front of the tub, closer to the action?

Mick
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trip would doubtless be attended with much hardship.''
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AnswerID: 408507

Reply By: Sand Man (SA) - Friday, Mar 12, 2010 at 07:13

Friday, Mar 12, 2010 at 07:13
Gitto,

Cable diameter is the most likely cause of your problem.

I have an AGM Battery mounted in the tub of my Colorado and have no problems.
I installed a Sidewinder Flyer to house the battery and this system comes complete with cables, anderson connectors and a built-in isolator. The cable is also 6m long but 100mm2 dia.


Bill.

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AnswerID: 408512

Follow Up By: Ray - Friday, Mar 12, 2010 at 08:40

Friday, Mar 12, 2010 at 08:40
Hi that sounds as if it is the trouble. Cable too small. My axillary batteries are mounted on the draw bar of my caravan. I am using 4 aswg cable (18.6mm2) and do not have a problem.
I believe that the standards association get a grip of the auto cable manufacturers and standardise auto cable just like any other cable
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Follow Up By: Member - Graham H (QLD) - Friday, Mar 12, 2010 at 09:26

Friday, Mar 12, 2010 at 09:26
100mm 2 Really? Thats pretty heavy
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Follow Up By: Sand Man (SA) - Friday, Mar 12, 2010 at 20:48

Friday, Mar 12, 2010 at 20:48
Ah, well picked up Graham.

10mm2 of course:-)


Bill.
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Reply By: Member - Graham H (QLD) - Friday, Mar 12, 2010 at 09:24

Friday, Mar 12, 2010 at 09:24
Try asking at Battery World for some 6 B & S cable They will know what you mean

Take a thick wallet Its around $10 a metre .
AnswerID: 408529

Reply By: fugwurgin - Friday, Mar 12, 2010 at 11:05

Friday, Mar 12, 2010 at 11:05
HI
I have put a second battery in the back of my rodeo (due to the ABS same as you). I have a 120amp isolator and ran 4b&s cable. I put in 2 60amp fuses (one at the isolator and one before the Aux battery. I was getting a voltage drop of about 1 volt. I took my fuses off and tried it, then only got a .15 voltage drop (much better). i replaced the fuse at the aux batt end with a 100amp circuit breaker and didnt bother about a fuse at the isolator end. Still only get a .15 volt drop.
The type of fuse i used is this type
fuse
Perhaps the terminals were too thin. im not sure, all i know is that taking them off solved my problem.

My suggestion based on my experience is make sure your fuse and associated wiring and housing, plugs, terminals etc are adequate, even though they may have a high amp rating they may still put unwanted resistance in the circuit if not of good quality.

And like others have said, the 6b&S is the minimum, 4 is better. And make sure you have a good earth, a full length earth back to main battery of same size cable is best (but adds expense)

hope you sort it out.
AnswerID: 408548

Reply By: Mandrake's Solar Power- Friday, Mar 12, 2010 at 14:27

Friday, Mar 12, 2010 at 14:27
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There ya go !!

Cheers

Steve

AnswerID: 408564

Reply By: Maîneÿ . . .- Friday, Mar 12, 2010 at 15:15

Friday, Mar 12, 2010 at 15:15
I use 1 B&S and get no voltage drop, one way to save money but loose voltage is fit cable that is too skinny, remember there's no such thing as too thick :)

Maîneÿ . . .
AnswerID: 408571

Follow Up By: Crackles - Friday, Mar 12, 2010 at 22:59

Friday, Mar 12, 2010 at 22:59
Agree Mainey. I ran 35mm squared cable to the 2nd battery in the rear then 16mm into the Anderson plug for the caravan/trailer minimising line loss. Improves charging with the added bonus that the winch & starter motor run far better off the two.
Cheers Craig...................
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FollowupID: 678557

Reply By: Gitto - Friday, Mar 12, 2010 at 21:05

Friday, Mar 12, 2010 at 21:05
Thanks for all the help I now have some areas I shall check out and see what I come up with.
AnswerID: 408618

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