thrushl

What Size Battery Cable?

8 posts in this topic

Alright friends, dumb question that all ya smart types know off the top of your head.

Ok, I need to replace the battery cables on my house batteries. Why? The ends are falling off and they look "cheap." I don't like ugly cables....

I have 16 220AH 6V AGMs wired in series/parallel. They are in two eight battery banks feeding two Xantex SW3012 inverters in a stacked configurations. Please, don't ask why... (Hint...DW like POWER)

Normally, this should be easy, EXCEPT Monaco failed to use battery cable that was labeled. They probably save money by buying it without the proper markings.... :-)

OK, this is big stuff but how big I don't know. I'm guessing 2/0 or 3/0 SGT.

Am I close? As you know, some of these are real short cables so I can't go lo large or I will never be able to bind them enough to install them.

Thanks in advance for the wisdom.....

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Assume these cables connect to the inverter(s).

If so, you need to determine maximum amp that you will be carrying AND total roundtrip distance from battery positive to inverter and inverter to battery negative.

Then, go to one of the many wire size/amp capacity tables to determine the proper minimum wire size using the 3% drop tables.

An excellent source of large-gauge high quality cable is welding supply companies. And, many can swedge the proper ends on for you-- it does require special tools.

Just put "welding cable" in your search engine and you will find some great sources.

One other way to tell is to find out the largest gauge cable that will fit in your inverter's connections if they are designed to clamp on the cable rather than use a fastener.

Brett

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Assume these cables connect to the inverter(s).

If so, you need to determine maximum amp that you will be carrying AND total roundtrip distance from battery positive to inverter and inverter to battery negative.

Then, go to one of the many wire size/amp capacity tables to determine the proper minimum wire size using the 3% drop tables.

An excellent source of large-gauge high quality cable is welding supply companies. And, many can swedge the proper ends on for you-- it does require special tools.

Just put "welding cable" in your search engine and you will find some great sources.

One other way to tell is to find out the largest gauge cable that will fit in your inverter's connections if they are designed to clamp on the cable rather than use a fastener.

Brett

Thanks Brett.

I knew this was your lane. I need both intra-battery cables and cables to the inverter. The inverter uses posts so test fitting will not work. My fuzzy math says total MAX MAX MAX AMPS worse case is 290. The longest cable run is approx 10ft with slack and routing.

I tried to use one of those tables you referenced and if I can read, it says 2/0.

With those numbers, does 2/0 sound about right?

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Here is a wire size/amp table-- plug in the numbers. http://www.powerstream.com/Wire_Size.htm Be sure to plug in the ROUND TRIP distance.

Looks like 2/0 will give you close to a full volt drop-- you want less.

Again, bigger is better. Goal is a 3% drop.

Brett

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Thanks Brett.

Decision made:

4/0 on longer run

3/0 on everything else.

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I would use 2/0 on the jumpers 3/0 on the parallel connectors and 4/0 on the long runs. Feed the positive off of one end and the negative off the opposite end. Use red and black heat shrink on the cables at the appropriate ends, makes it easier to identify polarity and reduces the corrosion factor.

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That's a great suggestion as the 3/0 jumpers may just be to large and stiff. THANKS

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In case you haven't already done this, take lots of pictures and make a wire diagram of what wire goes where.

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