Cable size between main & aux batteries?
Submitted: Wednesday, Oct 12, 2005 at 21:05
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Member - Drew T (VIC)
further to my post 27810 earlier in the week .... if you use much heavier cable between the main & aux batteries (eg: 2g .. 32mm2) then i take it you never fuse this cable as you would do if it was much lighter duty???
Reply By: Russel & Mary - Wednesday, Oct 12, 2005 at 21:23
Wednesday, Oct 12, 2005 at 21:23
Correct. Even with lighter duty cable I wouldn't fuse it. You really don't want any join that has potential to cause a bad connection. I've previosly just used light duty wire doubled up, but this arvo I joined the batteries with proper BIG cable. I have not had trouble before but heavier cable will allow full 80 amps to flow when needed. Rus.
AnswerID:
134379
Reply By: snailbait (Blue mntns) - Wednesday, Oct 12, 2005 at 21:27
Wednesday, Oct 12, 2005 at 21:27
Member - Drew T (VIC)
hi Drew
the larger in od the cable is the beter it caries the load from the Alternater to the batter it is just like a
water tap if you have a 8mm id pipe as against a 12 mm id pipe the 12 mm id pipe will let more
water through at the same pressure also the new vehicles must work on a higer voltage the old machines worked on 13.7 volts the new vehicles work on 14 voltes
when conecting the second batteries use the largest size you can afford between the batteries
AnswerID:
134381
Follow Up By: Mark T - Thursday, Oct 13, 2005 at 19:14
Thursday, Oct 13, 2005 at 19:14
When I started my apprenticeship as an auto electrician 35 years ago, system charging voltage was 14.2 volts and that was was what the voltage regs were set at. So, how long ago were the 13.7 volt machines made?
Cheers
MT
P.S. Your theory on pipe size does make good sense and is correct.
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Reply By: BenSpoon - Wednesday, Oct 12, 2005 at 23:31
Wednesday, Oct 12, 2005 at 23:31
Its still safer to fuse any +'ve lead. You can stick a couple of lugs and a 150Amp circuit breaker in the line pretty cheaply and easily. If it is a starting current flowing though the cabl I'd probably leave out the breaker though.
AnswerID:
134415
Reply By: 4X4Treker - Thursday, Oct 13, 2005 at 02:22
Thursday, Oct 13, 2005 at 02:22
Drew T
The heavier the cable the better I have run 35mm squared cable between the batteries on both the +ve and -ve sides and also to the body as
well.
I use an automatic isolation relay to separate the batteries when the engine is off and the 35mm cable goes directly onto the relay with the appropriate crimp lugs without any problem. and if you want to fuse it you can either instal fusable link or a circuit breaker as mentioned above.
Cheers
Treker
AnswerID:
134426
Reply By: Michael Carey - Thursday, Oct 13, 2005 at 07:37
Thursday, Oct 13, 2005 at 07:37
You should fuse EVERY cable that connects to a battery! The potential for fire and disaster is too great, especially with thicker cables. You might get away without a fuse for a long time, but if the cable ever shorts to the chassis......!!!!!
There are fuses available for this kind of application. I found fuses and a holder designed to go into large electric vehicles like
fork lifts and even "gopher" style people movers. An auto electrician should be able to help you out with this stuff.
You can see a "heavy duty" fuse and holder in this pic of my electrical distribution system I put in my Hilux.
http://www.users.on.net/~michaelcarey/pics/hilux/May2005/photos/photo18.html
You can never be too careful...
AnswerID:
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Follow Up By: Bonz (Vic) - Thursday, Oct 13, 2005 at 08:44
Thursday, Oct 13, 2005 at 08:44
Not so, the starter motor cables are never fused, neither are battery to battery cables in my experience.
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Follow Up By: Michael Carey - Thursday, Oct 13, 2005 at 08:55
Thursday, Oct 13, 2005 at 08:55
I stand corrected. You would be hard pressed to find a fuse for a starter motor and
winches.
BUT, having an unfused 2 ga cable running through an engine bay to connect two batteries (via solenoid or controller) can be quite bad.
If precautions are taken in regard to running it through conduit and protecting it from damage and heat, you will PROBABLY be OK. But I would never consider it for a 2nd battery mounted any distance away from the engine bay. Both ends of the cable should be fused as close as possible to the battery.
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Follow Up By: Bonz (Vic) - Thursday, Oct 13, 2005 at 08:55
Thursday, Oct 13, 2005 at 08:55
Hey Michael, That is an impressive array you have there, did you rewire the whole thing via that? What are the 8-10 fuses and 5 reays supplying? Looks a
well done setup. Very neat.
Add to what I said above, All down line circuits should be fused, i.e. Battery to load etc.
FollowupID:
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Follow Up By: Bonz (Vic) - Thursday, Oct 13, 2005 at 09:00
Thursday, Oct 13, 2005 at 09:00
The cable I used battery to battery isn't fused, but has very substantial insulation and is routed away from excess heat, also as I use it to start from second battery. I use a fusable link for all other ccts from the second battery. Hey you know stuff...we should compare notes!
FollowupID:
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Follow Up By: Mainey (WA) - Thursday, Oct 13, 2005 at 16:47
Thursday, Oct 13, 2005 at 16:47
Your wiring distribution system appears to look really neat and tidy, yes obviously not done this way by the usual auto sparky.
However the idea of using a fuse when paralleling two batteries which most times are generally close together, is not a necessity UNLESS there is some chance of a short or difficulty in attaching or stabilising the leads within the installation.
That said you should always fuse between the battery system and the distribution link for the load/s applied to the battery system.
Some of the (quality) expensive battery isolator manufacturers don't even specify to use an inline fuse in their dual battery systems!
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388545