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Old 09-03-2011, 10:28 PM
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Battery Isolator Wire size?

In the process of installing a second battery in my truck to run my airbag compressors and purchased a 200 amp battery isolator and was wondering what size wire I should run between my batteries and isolator? I dont think the wire needs to be as big as the wire going from the battery to the starter? does it? I was planning on using a 8 guage wire between . will that be sufficient? or does it have to be a 4 guage?

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Old 09-03-2011, 11:14 PM
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I would go with the 4 or heavier, but here is a sizing chart for you to help make up your mind.
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Old 09-04-2011, 01:10 AM
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Quote:
Originally Posted by 67Elcamino
In the process of installing a second battery in my truck to run my airbag compressors and purchased a 200 amp battery isolator and was wondering what size wire I should run between my batteries and isolator? I dont think the wire needs to be as big as the wire going from the battery to the starter? does it? I was planning on using a 8 guage wire between . will that be sufficient? or does it have to be a 4 guage?
Bigger wire gauge has its advantages but can cause problems w/fitment and routing in some cases. If there are no problems routing larger wire, there's no real downside to doing so, IMO. The alternator output wire going back to the isolator (if that's the plan) should be made larger.

The bottom of page 1 shows some recommended gauge/amp ratings depending on the alternator capacity that may be of use to you. DC current "likes" more rather than less strands for any given wire gauge.
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Old 09-04-2011, 08:13 AM
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Did your air bag compressor come with any specs about what the amperage draw is? There are tables for sizing wire per amperage draw. I would go one size AWG bigger than what is required for safety sake.

Vince
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Old 09-04-2011, 10:05 AM
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Wire Size

http://www.countryhomescampers.com/p...structions.pdf

Here are instructions that cover most alternator applications. See the wire chart/breaker sizing recommendations. Make sure to use a circuit breaker. Don't make the mistake of sizing the wire off a voltage drop chart as some dudes do, it does not take wire heat/insulation temperature rating into consideration. Use automotive grade wire with the highest temperature rating you can find. Although a bit more expensive, marine rated wire from a boat store is the best. The marine cable terminals are also way higher quality than the cheap junk that most auto part stores carry. Also as others have mentioned, using one size bigger wire over the chart listing adds in a safety factor.
olnolan
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Old 09-04-2011, 12:17 PM
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Thanks guys

Another question I see some wiring diagrams on the Isolators state that the wire goes from one battery to islolator to the other battery instead of from the alternator to isolator to battery.. Is there a difference? if going fro alternator to isolator how do you run a 4 guage wire from the alternator? Just seems a big of an exaggeration comiing from the alternator
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