# Battery Connectors



## ronin4sale (Jan 29, 2008)

Personally I don't think the cost savings would be worth #1 the time and effort and #2 the possibility of error, but thats just how I feel about it as time = money to me.


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## Wayne Tanner (Jun 18, 2008)

Note that the current carrying capacity of a conductor is mostly a surface phenomenon. As such, braided wire can carry more current than a solid one of the same wire gauge. Braided cables are a lot more flexible and have less stress when you send it around.


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## Coley (Jul 26, 2007)

I made all of my terminals from copper tubing, flattened, drilled and then soldered to the cable.
72 volt system, no problem.
Higher voltage, don't know....


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## ww321q (Mar 28, 2008)

Coley said:


> I made all of my terminals from copper tubing, flattened, drilled and then soldered to the cable.
> 72 volt system, no problem.
> Higher voltage, don't know....


That's a good cheap way to make ends to ! Lets see , I need over 40 lugs at $2.59 each . Thats over a $100 . J.W.


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## gasless (Jul 10, 2008)

I think its a good Idea


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## e_canuck (May 8, 2008)

Hi guys.

I am not even close to making cables here. But I have a question.

A solid bar seem fast and economical. I like it and i own several pounding tools. Cable connections would allow some movement from vibrations. Would you need to mount the batteries solidely to prevent damage to the posts or loosening of connections?

DP


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## iss407 (Dec 6, 2007)

I assume you'd want to elliminate as much movement as possible. It's a good idea to keep the batteries very well secured anyway. I don't want any "wiggle room" between the connection and the battery because that just adds resistance to the current.


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## theboy16 (Feb 28, 2008)

Wayne Tanner said:


> Note that the current carrying capacity of a conductor is mostly a surface phenomenon. As such, braided wire can carry more current than a solid one of the same wire gauge.


The skin effect, as its commonly referred to, applies only to AC current, and practically speaking, applies only to high frequency AC current. the higher the frequency, the more the current tends to travel on the outer surface. common north american electricity, which runs at 60Hz, has a depth of 8.57 mm

more examples:
10 kHz - 0.66mm
100kHz - 0.21mm
1 MHz - 0.066mm
10MHz - 0.021mm

so there's no need to worry about the skin effect when dealing with your DC battery set up.

i have read before, however, that the solid copper would apply undue stress to the battery terminals due to vibration, bumps, and bounces, i hope this is false, because i really like the copper pipe idea.

steph


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## Qer (May 7, 2008)

theboy16 said:


> i have read before, however, that the solid copper would apply undue stress to the battery terminals due to vibration, bumps, and bounces, i hope this is false, because i really like the copper pipe idea.


It's definitely true. Material stress applies to anything that's vibrating and where the construction isn't designed to handle the stress. The battery poles are definitely not designed to handle the forces introduced when a whole battery pack shakes so unless the batteries aren't SERIOUSLY bolted down, the poles will probably break eventually.

Two ideas that bubbles up in the back of my head is to limit the stress in one of two ways, or, of course, a combination of the two:


Strap the batteries together two by two and use rigid connections per pack and use flexible connections between the packs. It will definitely be much simpler to make sure that several small packs are rigid enough for the pipe idea to work than trying to make a pack of 20-25 batteries rigid enough to not risk the poles to break.
Do the tubes V, N or W-shaped so they can bend. That way the poles only has to handle the force needed to bend the tubes rather than keeping the relative position between the batteries.
I definitely think that straight bars between the poles will bring havoc and destruction to the batteries, especially if you live by a gravel road like I do...


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## ElectriCar (Jun 15, 2008)

I'm an electrical contractor so I may can help here a bit. Here's some ideas to kick about. 

One idea for making your own cables is to use a mechanical lug. http://rds.yahoo.com/_ylt=A0WTeffPcYBIfbwAUyCJzbkF;_ylu=X3oDMTBpc2VvdmQ2BHBvcwM3BHNlYwNzcgR2dGlkAw--/SIG=1gdmpp1c8/EXP=1216463695/**http%3A//images.search.yahoo.com/images/view%3Fback=http%253A%252F%252Fimages.search.yahoo.com%252Fsearch%252Fimages%253Fei%253DUTF-8%2526p%253Dmechanical%252520lug%2526fr2%253Dtab-web%2526fr%253Db1ie7%26w=200%26h=168%26imgurl=www.goodmart.com%252Fimages%252Fprodimages%252Fideal%252F1FS120.jpg%26rurl=http%253A%252F%252Fwww.goodmart.com%252Fproducts%252F84366.htm%26size=14kB%26name=1FS120.jpg%26p=mechanical%2Blug%26type=JPG%26oid=f128482c3c716122%26no=7%26sigr=11aidqqam%26sigi=11jf5s8qg%26sigb=12th0lstf&tt=219

Here's another multi connector. http://rds.yahoo.com/_ylt=A0WTeffPc...1a3m2130&sigi=11jerpdo2&sigb=12th0lstf&tt=219

Those will do the job but you need to check them after you tighten them and run it a while. Be sure you get BRONZE type and not the aluminum ones. If you mix aluminum lugs, which are lighter weight and copper wire you'll create a galvanic reaction resulting in corrosion.

The other means to fabricate cables is to buy a crimping tool and lugs. The tool we use can be had for about $150. It is a professional tool and looks like a bolt cutter. Burndy # MRC840 http://cgi.ebay.com/BURNDY-MRC840-M...ryZ66987QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Here's one on ebay. You can get the lugs and this or similar tool at the suppliers below.

Here's a list of contractor supplier near us. Some likely to be in your area are City Electric Supply. However they are often higher priced due to the fact they are often the ONLY supplier in smaller towns.

All Phase Electric, Graybar (Large national company with good pricing), Consolidated Electric Supply (CED) are also relatively large companies. You'll also have some home grown mom&pop suppliers as well. Check the yellow pages under electrical.

One final thought. Once you know what you need, ask them for a price. We do it all the time. Often you'll pay more than necessary if you don't work them a bit. Ask them to quote your parts list. Shop it with a couple other companies and you'll see what I mean. 

Hope this helps.


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## morvolts (Jun 19, 2008)

Not to dispute the use of mechanical connections but Ive found that its not a good idea for a permanent connection thats subject to vibration and alot of cycling(heat and amperage fluctuation's)
Aluminum lugs will be made of an alloy and will be marked "Cu" if compatible with copper cabling.
I do alot of battery strings for Telco equipment and its speced to be long barrel compression lugs with heat shrink
overlapping the "shiner" portion of the cable.Most specs even require the special dies that emboss the die# into the lug when its crimped so theres no mistake its the right size. I have done alot of analysis thru infrared scans and temp recordings and this is really the best connector.Another source that easy to get to via mail order is WW Grainger.


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## ElectriCar (Jun 15, 2008)

Sounds like you're on top of things. Yea, our buildings don't move and shake thus the reason for saying they need to check the connections again. 

OTOH, if saving money is more important than "care free" connections, the lugs may be cheaper and you don't need a $150 crimp tool. I say may be cheaper as I haven't checked prices lately of the mechanical lugs or crimp lugs. Re shaking etc. If the battery bank is secured properly so it doesn't bounce and shake, the ML's may be a viable option.


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## morvolts (Jun 19, 2008)

you are correct on that but they are still subject to extreme cycling especially when the battery voltage drops.

We have done alot of testing and found that the 10,000 psi crimp will actually reform the copper into a solid conductor
at the point of crimp.TypeW cable normally needs one size larger than the AWG for a good fit without loosing any cir mils.


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## Taztech (Dec 5, 2008)

Coley said:


> I made all of my terminals from copper tubing, flattened, drilled and then soldered to the cable.
> 72 volt system, no problem.
> Higher voltage, don't know....


What size Cable did you use? I was thinking of doing the same thing using 2/0 welding cable, only I was going to crimp and solder them then flatten and drill a hole. Will this work for a 144 volt system that may have momentary current of 500A? or should i just go with buying lugs?


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## Coley (Jul 26, 2007)

I used 2.0 cable and it must be working well, as I have no warm connections.

You could also crimp the homemade terminals, if you wish.

I made mine this way, as I wasn't sure what I was going to have to change.

The ends can be removed, if needed and put on a longer, or shorter cable.

I am only pulling a little over 300 amps for the most part.

I don't know what the limit would be, but if they are well soldered, they should be OK.

Some of the cables that I have found, from applications, were soldered only as well.


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## dtbaker (Jan 5, 2008)

e_canuck said:


> A solid bar seem fast and economical. I like it and i own several pounding tools. Cable connections would allow some movement from vibrations. Would you need to mount the batteries solidely to prevent damage to the posts or loosening of connections?
> 
> DP



If you use flat strap, be SURE it is not just a straight run; you need a couple bends so that it can flex and bend a little without stressing the posts.


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## ZenDaddy (Jul 22, 2008)

I have to recommend reading the diy wiki. #2 cables with soldered ends made of copper pipe and soldered (sweated) have worked extremely well for me. No heat, zero (unreadable on my meter) resistance. I have negligable voltage drops.

Worth a look in my opinion.

http://www.diyelectriccar.com/forums/showthread.php?t=688

ZD


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## BikerA (Jan 9, 2008)

I used 1/2 thin wall copper pounded flat and insulated with heat shrink. I had a post melt probably because the heat shrink prevented full clamp down. My amp meter will peg at 500 easily so it must be carrying the current.


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