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Author Topic: Battery bank cables, what size to use?  (Read 3502 times)
kyle4501
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« Reply #15 on: May 28, 2008, 08:19:16 PM »

Whatever wire you use, it would be prudent to make sure the insulation is rated for your intended use.

I don't want to even think about the consequences if the insulation fails when you have that many batteries connected together.
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« Reply #16 on: May 29, 2008, 04:49:39 AM »

Whatever wire you use, it would be prudent to make sure the insulation is rated for your intended use.

I don't want to even think about the consequences if the insulation fails when you have that many batteries connected together.


Kyle brings up a good point!

Make sure you also consider your routing and attachment points to eliminate potential wear through points.

I deal with a lot of high voltage dc plant issues(another hat I wear) and we probably spend more time on securing and isolating than any other part of an installation.

Be Safe!

Cliff

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H3Jim
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« Reply #17 on: May 29, 2008, 06:54:11 AM »

and when you are using wrenches to tighten the cables, do all the positives first, then the ground.  That way if the wrench is on the positive, and it touches the frame, you won't weld the wrench.  With hundreds of amp hours in these batteries, they can heat something up to red hot really fast.

Don't ask me how I know this.....
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Jim Stewart
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Len Silva
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« Reply #18 on: May 29, 2008, 07:15:11 AM »

I would strongly recommend that you not use the hammer type crimper.  I have many years experience with heavy power installation and suggest you find someone who has the proper hydraulic crimper to make up your connections.

There is more to it than just a good mechanical connection.  When done properly, the wire and connector are fused together under tons of pressure, essentially becoming one unit.

In addition, the compression tool and dies must be properly matched to the connector you are using. In other words you cannot properly crimp a Burndy connector with a T&B tool. Both are very good brands. Also, be sure to use a light coating of anti-oxide on the wire before making the crimp.

Len
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« Reply #19 on: May 29, 2008, 07:27:45 AM »

When you are working around batteries please remove all your rings  I had a accident several years ago where my wedding band was shorted out with a wrench and melted on my finger and did that hurt for a long time
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TomC
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« Reply #20 on: May 29, 2008, 08:07:52 AM »

All the talk of venting can be eliminated by just using AGM batteries.  They don't vent, plus they can be mounted in any position, except upside down.  Good Luck, TomC
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H3Jim
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« Reply #21 on: May 29, 2008, 09:26:39 AM »

While AGM's don't normally  vent, they do have vents on them, and can under extreme situations, vent.  They are the best choice however.
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Jim Stewart
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« Reply #22 on: May 29, 2008, 02:30:17 PM »

I guess I'm just in a funny mood.  Sorry.  H3Jim....hydrogen gas goes up, soosss should'nt the batts vent to the top with a dedicated explosion-proof fan located and pulling air in from the bottom?  Damage can occure...and with your setup....BOOM!  Hate to nitpic, but stuff happens.

Nick....sorry again....the chart provided (I believe) is sized for a 3% voltage drop, which over time may adversly affect the invertor?  Less then 1% is better. We found this out the hard way with our solar homestead years ago.  $$$.  Upsizing the gage of cable saved us a lot of energy.  Smiley Smiley Smiley
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rv_safetyman
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« Reply #23 on: July 02, 2008, 05:47:59 PM »

I thought I would update this thread. 

It got a bit off subject, but the replies confirmed that I had a wire gauge issue.  I had used 6 gauge for my 30 foot run and the 12V alternator was rated at around 130 amps.  I was getting very low amperage to the battery as measured by my Bogart Tri-metric battery "state-of-charge" meter.

I bought some welding cable off of Ebay.  It was stated as being 1/0, but my 1/0 ends were almost impossible to install, so it may have been 2/0.  I installed the cable with 200 amp fuses at both ends and it sure made a difference.  I now get a net of over 70 amps (probably 20 amp draw most of the time for a gross of 90 amps) when the batteries are down to about 50%. 

It sure seemed strange to put such large cable on such a small alternator (22SI size) with equally small terminals, but the wire tables do not lie.

Jim
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Jim Shepherd
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« Reply #24 on: July 03, 2008, 04:43:06 PM »

the studs at the ends are only a small part. had you only been going 2 or 3 feet you could run a small cable. the 30 feet is killing you and the small wire has too much loss through it. I just replaced all my battery cables as the insulation was coming apart. took about 25 feet to go 8 by the time it went up and over and around so I had to run 4/0 cable. hated the price but I know that it will handle the load.
steve
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rv_safetyman
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« Reply #25 on: July 04, 2008, 07:04:23 AM »

Steve, your wire size agrees with the recommendations of Prestolite/Leese Neville (http://www.prestolite.com/literature/tech/alts/TSB-1001_wire_size.pdf). According to that table you are good for 250 amps.  In my case, I was not able to easily run anything over 1/0.  That gives me a capacity of about 125 amps for my 30 foot run.  Given my alternator, that is probably OK
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Jim Shepherd
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coachconverter
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« Reply #26 on: July 04, 2008, 12:03:08 PM »

If I may give an informed endorsement, try these guys.  Give them your specs, they cut, crimp and wrap your cables and they look as professional as anything.  Quick turnaround too!

Mike Nediano
Genuinedealz.com, LLC
866-970-3325 toll free
http://shop.genuinedealz.com

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JohnEd
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« Reply #27 on: July 04, 2008, 02:55:12 PM »

When I first went to school we had to solder everything.  Crimp wasn't on the menu.  Later when it was discussed it was determined to be less of a quality connection that soldering/silversoldering.  It was just way cheaper in terms of man hours and also a crimp is better from a QA point cause soldering takes skill.  Just remember and NEVER forget....no acid flux or acid core....only rosin.  Don't forget that.

About that welding cable.  You may want to rethink that a little.  Fine stranded copper is a real plus if you have to bend the wire/cable like maybe ever.  It has a serious drawback and that involves batteries.  Battery acid dissolves copper and the rate at which it dissolves copper is kind of a constant according to the acid concentration.  Now if you have a solid copper wire... lets say it will be eaten through in 100 units of time.  If you have 2 strands and same gauge....it will take half as long.  If you have 100 strands, same gauge, it will take 1 unit of time or one one hundredth the time.  If acid environment is not an issue....go stranded.  All bats eventually start out gassing acid and the terminals start to grow white stuff.  I use it but I seal it in shrink tubing after a liberal coating of silicone grease to the wire part under the shrink.

HTH

John
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« Reply #28 on: July 04, 2008, 03:53:44 PM »

Good comment aobuthte battery outgassing.  I used AGM's so thats not an issue.  Althogh they can still outgas, they are much less likely.  and I mounted the inverter high up in the compartment, and the batteries covered, are at the bottom and vented down.

Ahh..Yes... But AGM's can go into TNM ( Thermo Nuclear Meltdown ) and explode after
swelling up casually and making a hissing noise.

My preference is to separate the battery compartment from where the inverter is mounted. You MUST cool these inverters when they are running and a closed up
compartment is a bad idea. They can get really hot whether charging or inverting.
Keeping that extra heat away of the vicinity of the batteries is just a good idea.

The other reason is that a $1k to $4k inverter is too easily destroyed by a $50 battery that takes a dump or starts venting.
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grantgoold
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« Reply #29 on: July 04, 2008, 04:45:34 PM »

The size is clearly described in the installation manual of your inverter. I chose to go with 4 aught big boy cable. This stuff is hugh but worth every penny as you consider a fire in the bay with all the electrical and it makes sense. The biggest challenge was finding good quality ends and then a crimper. I would buy my cable on the e place ($4 a foot) both black and red and then take it to an industrial battery supplier and have the professionally crimp the ends. I was very happy with the end result. It did cost be about $250.00 for the entire cable set up from bank to switches to inverter. I like the comfort knowing that my system is safer because I spent the money up front.

Good luck!

Grant
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Grant Goold
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