# Sizing battery interconnect cable



## Explorer (Dec 2, 2003)

I have four Trojan T-105 6volt, 225 Ah batteries in a vented box I constructed. They currently connect to a 1500 watt 12 volt modified sine wave inverter and I shortly will be adding a 1100 watt 12 volt pure sine wave inverter in parallel. I normally will not exceed 800 watts usage from both inverters with surge not over 1500 watts ever.

I will be adding two more Trojans like above in a separate box located about four feet away for a total interconnect run of about six feet. I think current should be drawn equally from all batteries when needed. What cable size do I need for 6 foot interconnect cables?


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## Jim-mi (May 15, 2002)

. .4\O . . .

Ok you asked.................
You can't go wrong using the Big stuff on 12v systems (assuming that). . . . or for that matter Any battery system.

You might **calculate** for smaller but in the long run the big stuff wins out.


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## Explorer (Dec 2, 2003)

Thanks. I thought about this problem yesterday and came to a lesser conclusion. I know you are correct, bigger is always, mostly, better! I was thinking of using 2/0 for both leads as that would carry twice the max amps I should ever use on surge. I am still concerned about the connection of the charge controller and the inverters as I don't want to draw power only from my main four batteries and then have power flow unequally from the two "remote" batteries into the main bank (If that makes sense). 

Why do expansions become more complicated than originally thought?


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## Jim-mi (May 15, 2002)

Then figure a way to put those *two* side by side with the others.
If you can't, then use Big wire.


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## Explorer (Dec 2, 2003)

I didn't think I had explained myself clearly. I'm going to use big wire. I guess I connect my inverters, charge controller and the "big wire" to a single terminal for both positive and negative. Hopefully that will keep the load equal on all six batteries.


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## SouthernLiving (Sep 16, 2008)

Explorer said:


> They currently connect to a 1500 watt 12 volt modified sine wave inverter and I shortly will be adding a 1100 watt 12 volt pure sine wave inverter in parallel. I normally will not exceed 800 watts usage from both inverters with surge not over 1500 watts ever.


You really shouldn't try to run that modified sine wave inverter parallel with a pure sign wave inverter. Even if they are in phase they will output different instantaneous voltages. They are both 120V RMS but that doesn't mean that they wont buck each other. 

On the wire question, 1500W/12V=125A. Provided you are less than 100 feet or so from the batteries #1/0 AWG or better will do fine for wire size.


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## Explorer (Dec 2, 2003)

> You really shouldn't try to run that modified sine wave inverter parallel with a pure sign wave inverter.


They will be powering two totally independent circuits that are not inter-connected to the grid. One for the house and the other for the shop about 50 feet apart. They both are connect to the same batteries.


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## SouthernLiving (Sep 16, 2008)

Ok I gottcha. Scratch my earlier post.


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