My Battery Bank Question for Today, Cable Sizing?

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Rooftop Wind Turbine
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My Battery Bank Question for Today, Cable Sizing?

Postby Rooftop Wind Turbine » Mon Nov 28, 2011 12:29 pm

>> Hello Samuel, Thanks for taking my call last night and all the emails were
>> great. Since you made your Battery Bank video tutorial the price has
>> gone up a bunch. I started to think of going to 16 batteries in
>> my battery bank.

>> If I do that will I need to go with larger cable and if so, what size. I learned
>> a bunch from your emails about parallel circuits and voltages. So I think I
>> know the answer already but just playing it safe. I have been reading the
>> inverter manual and see a bunch of confusing info in there. Thanks, Bill

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Hi Bill,

It's good to read the inverter book but will cause lots of extra un-necessary communication and support work for both of us. That is all very generic and global information that will apply to all kinds of configurations not necessary to the support and install of what we are doing specifically.

So, stick to my information, drawings, and direction as completely as possible. Don't entertain drawings, specs, or directions from other sources.. it will just muddy the water and cause distraction or worse cause a system failure. I only focus to what is necessary and appropriate to my system and the quick training and installation of it. There's nothing general or not required in that info from me.

A 4/0 wire will carry up to and beyond 12kW of power, we are only putting in a 4.2kW system. 4/0 would be very unnecessary. A perfect example of why the manufacturers info causes extra worry. Worse are the multiple battery diagrams using 12v and other un-related stuff that doesn't apply.

2 AWG is fine for the 4,2kW with 8 batteries but is at that config not so heavy duty.. just adequate. Now that the HomeDepot has gone up in price so much there's no steal on that cable like before.. :(

2 AWG has proven to be fine for 16 battery banks as well but at this point based on actual testing and experience the 2 AWG is being upgraded on systems over 4.2kW and 8 battery bank.

- 2 AWG is appropriate on systems up to 4.2kW and 8 battery bank.

- 2/0 AWG is recommended on systems above 4.2kW and 8 battery bank.

- 4/0 AWG is recommended on systems above 10kW and 8 battery bank.

*These are updated recommendations. We have many, many, systems in the field that perform fine with 2 AWG which are above 4.2kW and 8 battery bank.

I just wired one using 2/0 all the way on a 4.2kW with 12 battery bank and it was a nice heavy duty touch on the system. Probably $100 of copper upgrade well placed at the heart of your system. Given the lack of great price on 2 AWG cable now I am updating my recommendations to this.

You can buy it in 50' lengths here and it comes in 25' lengths if you find you need that some time. Here's part numbers and pricing where I am sourcing these days. 50' will leave you some left over and 25' will not be enough to finish...

The last item, cable cutter, can probably get $20 or so cheaper at Home Depot or Lowes.

1ea...BLACKSTONE 2/0 x 50' Cut/Boxed Welding Cable..50Ft
SKU: 0812017................................$264.00ea... $264.00
http://www.fastenal.com/web/products/de ... ku=0812018


5ea...BLACKSTONE 2/0# Cable Lug With 3/8" Stud Hole.....2/pk
SKU: 0844022...................................$4.52ea... $22.60
http://www.fastenal.com/web/products/de ... ku=0844022


2ea...2/0 5/16" Max Non-Plated Lug.....................10/pk
SKU: 0717079..................................$21.30ea... $42.60
http://www.fastenal.com/web/products/de ... ku=0717079


1ea...BLACKSTONE Welding Cable Lug Crimper Hammer Style..
SKU: 0844004..................................$25.37ea... $25.37
http://www.fastenal.com/web/products/de ... ku=0844004


1ea...16-3/4" Red Handle 350MCM Capacity Utility Cable Cutter
SKU: 0252460................................$105.22ea... $105.22
http://www.fastenal.com/web/products/de ... ku=0252460

Anyone wanting a small wind turbine, fill out the contact form and I can connect you with the dealer for your area. There are still areas open in most states for new dealers but many counties and a few entire states are taken up and several people are saying they are going to get their territory. So, if you are interested in becoming a dealer fill out the same form and we can see if your area may still be open.

Thanks, Samuel H.
Last edited by Rooftop Wind Turbine on Thu Dec 01, 2011 3:31 pm, edited 1 time in total.

User avatar
Rooftop Wind Turbine
Site Admin
Posts: 233
Joined: Sun Nov 23, 2008 1:48 pm

Preparing Winter Install, Roof Conduit Pictures?

Postby Rooftop Wind Turbine » Mon Nov 28, 2011 12:51 pm

>> Sam, After the last conversation with you I am ready to install the solar
>> panels and wind turbines. I am having a roofer come out this weekend
>> to mark the rafters like we talked about. I am getting all my hardware
>> lined up and ready to go. Is there any pictures of the conduit that you
>> use on the roof for the turbine and solar panel wiring? You explained it
>> really well but if there are pictures would be GREAT. Your technical
>> emails were very good. I have learned so much. Thank You, Jim.

Hello Jim, The legs are 38" long and then the area from there to the peak is variable based on how steep the angle of the roof. Probably about 10"

They have stud finders now that can show you the exact edge of each truss or rafter. Stanley makes one that I have. I think they are ultrasound. You may get one and try it, see if it will save you lots of time & materials by marking the spots very accurately.

Yes, the roof work with the mounts and wiring can be done early if you like. The panels rails as well... kind of same thing.

This attached document will help you with identifying some of these parts and pieces and includes part numbers if you source from Grainger. You may be able to make a complete parts list and find a local electrical supply. That approach will save you money over Home Depot and Lowes but requires a bit more organized approach.

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Anyone wanting a small wind turbine, fill out the contact form and I can connect you with the dealer for your area. There are still areas open in most states for new dealers but many counties and a few entire states are taken up and several people are saying they are going to get their territory. So, if you are interested in becoming a dealer fill out the same form and we can see if your area may still be open.


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