I know that it's best to have the cables connecting the batteries the same length. What about the cables that go from the battery to the inverter? If one is at the back of the battery bank and one is at the front, I can have the one at the front 18" long, but the one from the back will have to be 2 1/2 to 3 feet. Does this mean that I need to match the length and have 2 1/2 to 3 feet of cable coming from each side, or does it matter?

Seems like I read somewhere that it does....

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Everything I have read says that the cable lengths should be equal for both charge controller to battery and battery to inverter connections. They should also be the biggest possible and shortest. Remember these connections will transport large amounts of AMPS and if you skimp you may have at worst a fire hazard and more than likely poor performance of your system.

I agree with Raymond, the must be the same length as well as short as possible, heavy as possible.

Sounds good. I'll use the maximum possible size allowed that will fit in the MidNight controller.

Can you guys make a suggestion on battery cables? My bateries are arranged so that each cable can be 9" long. The battery has a post with a screw.

Is there an online source that will do custom cable sizes where I can order 9"cables of very large sizes to connect the batteries and to connect to the inverter?

I have the fuses that will go before the charge controller, before the batteries and before the inverter. So some of the lengths will be very short, just long enough to go from the device to the fuse screwed to my board. The ones coming from the panel to the controller I'll have to swag myself. Is it acceptable to just use pliers and crimp thos on or do I need the special crimping tool?

Okay this will sound sound far out there but if your good with tools, IE hammer , press , and soldering you can make your own lugs and whatever size wire. Just make sure your size up the material. I use copper pipe to make my own lugs , Because I am tired for being charged $7 for 2 lugs. When a 10 foot peice of copper pipe or Coiled pipe will make a ton of lugs. Just Solder the wire into the DIY lugs.1/4 inch pipe works fine for 4 gauge wire..3/8 for 2 and 1 gauge....1/2 for 0 or 1/0

I have the same issues with length on my inverter, neg is about 15 inches, pos is much longer, but I'm using large car battery cables, whatever size they are....the inverter runs everthing (including the refrigerator) just fine...I agree they should be short and same lemgth, sometimes, ya just can't do that...being the neg should be connected at one end of the bank, and the pos at the other end of the battery bank to config properly,,,

Reply to Dale Marshall,

Your suggestion that we use copper tubing (pipe) to make terminal lugs is so ingenious that I felt stupid because I did not think of doing the same thing.

I have been making and re manufacturing terminals out of copper washers and other scrap which is a lot more work. Using copper pipe makes a custom connector and a better one besides. Wiring up the battery bank is now a custom made job and saves considerable dinero. I wonder if by using our trusty soldering iron we are not getting better connectivity, (conductivity)?

Thanks a million Dave! I am indebted to you for the3 rest of my life.

I have been always untrusting on crimping wire lugs..I figure in the real world, Where electricians install in houses and building the wire may never be touched or moved around. But in our Solar applications things do get moved around.  But for Batteries. I figure it one of the best way to make connectors. Definitely 100 % conductive.    

Supposed to be as equal as possible for losses and resistance with length..

I cut 2 AWG wire 2 feet (24") long and have 2 sets ready to go for my copper battery bussbar..


My battery bank will be 600-700 ah.. pending on the battery I will need at least 3 sets (of 6v 220ah) or 7 WM DC27 batteries.. My copper bussbar will hold upto 9 connections..

If I get my copper board mounted lets say 16" off the floor (just above a bttery box) on the wall I will have about 18" of 'swing' length to either side or down the middle.. I should have room for 5 batteries (or sets) turned sidways in front of the copper bussboard.. I will be buying 16 foot more of 2 AWG to have on hand and compression copper terminals.. (#BTC0208) for install day as well.. (since my local  HD and WM is 120 miles away I don't have options)..

My inverter wire is 3/0 and runs thru a Bluesea 250 amp fuse, then Bluesea 350/500 amp switch the length of wire is 42".. granted I'm running a 2000w 12v inverter.. The 3/0 wire will be cut on install day to as short as possible and as even as possible as well..

I used a piece of 3 foot audio wire (MP3 headphone wire) to pre-figure my wire lengths if that helps anyone..

I dug out my board to take/show a better picture.. both wires are 2 AWG and 24" long.. Also note the 5" gap between the copper bussbar..

This shows that I get a 19"+ of wire swing even with about a 4-5" drop/angle from the board.

When I did my figuring like I said I used a short audio wire (measured to 3') to figure my max length of wire I felt comfy with MAYBE using.. I settled on 24" as a basic starting point and hopefully (90% sure) all my batteries will get that same 24" wire..

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