# Battery Cables for your EV



## jstack6 (Jul 26, 2007)

Here's some wire sizes I found on line. The new EV's use AC motors for great efficiency and regen braking. They also use much higher voltage so the wires can be smaller. Most of use EV drivers use DC and 120 volts or so. The 2/0 is very good. Be sure to make the crimp very solid and use the correct crimper for the lug. They vary a lot.

http://www.windsun.com/Hardware/Wire_Table.htm

Cross reference of AWG (American Wire Gauge) sizes to metric (mm)

AWG mm2 AWG mm2 AWG mm2 AWG mm2 
30 0.05 18 0.75 6 16 4/0 120 
28 0.08 17 1.0 4 25 300MCM 150 
26 0.14 16 1.5 2 35 350MCM 185 
24 0.25 14 2.5 1 50 500MCM 240 
22 0.34 12 4.0 1/0 55 600MCM 300 
21 0.38 10 6.0 2/0 70 750MCM 400 
20 0.50 8 10 3/0 95 1000MCM 500


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## KiwiEV (Jul 26, 2007)

I've just got word back from my battery cable supplier here in NZ that they don't have 2/0 sized cable, only 1/0 (50mm2). Does anyone think that would be suitable for my 144 volt setup? 
The highest current draw I expect will be around 250amps foot hard down as I'll be limited with unimpressive 12V flooded batteries.
It could save me a fair amount if this size is suitable... Opinions anyone?


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## Mannyman (Jul 26, 2007)

I wouldn't pick that area to skimp on. It may work but why chance it?
Check welding supply vendors.
Either way, your success will inspire others,


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## rbgrn (Jul 24, 2007)

How far of a run is it from +144V to Controller +? That really is the biggest factor. At 36kwatts, every foot counts!


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## moldiebrownie (Aug 29, 2007)

At 144v it seems way too inadequate to carry the amps you might encounter. I run a 120v setup and when I take off my guage hits 350-400 amps easily. I have not seen anybody using this small cable except for maybe lower voltage setups like 48v. Heres a guy thats running 144v also and he decided to do 4/0 cable! He states, "_*In order to handle the extremely large currents that could someday peak at nearly 1000 amps, #4/0 wire has now been installed and routed from front to back.*_" http://www.saabrina.blogspot.com/ Hes the only guy I've seen using this monster cable but almost without exception its always 2/0 welder's cable. 1/0 cable to me just sounds like too much resistance and your cables and connections might heat up...not to mention a good voltage drop.


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## KiwiEV (Jul 26, 2007)

Thanks for the input everyone. I'm going to use 2/0 (70mm2) cable for sure. 
I've run around town and sourced pricing on the stuff and will purchase it as soon as those blessed Money Gods smile upon me.
Thanks for convincing me out of it - that could have been a performance-choking mistake.


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## Adrian (Jul 26, 2007)

Pack voltage does not determine cable size, battery current does.

For the short interconnects between batteries I'm using 1" x 1/16" copper bus bar. $30 was enough to wire my 19 batteries with plenty leftover. Longer runs between battery boxes are done with 2/0 cable. The controller/motor loop is 4/0 (1000A max from the Zilla!).

1" x 1/16" is approx. 40mm^2, which is slightly larger than 2 AWG wire. Even after a long uphill run, the bus bars are not even warm... My typical current draw is about 100A. I do 20-30 seconds of 200A-300A on hills, and my controller is set to 400A max.

Bus bars keep cool better than insulated wire. It allows higher peak current draw. There was a short discussion about this on the EVDL recently.

Another plus is how quick and easy it is to make interconnects. It's also useful for very short runs like between a circuit breaker and contactor in a sealed box, where 2/0 cable with attached lugs can't be used.

1) Cut bar to length
2) Drill holes in the ends
3) Put heatshrink over the center
4) Bend into shape (at least 1 bend to prevent stress on battery posts)
5) Shrink the heatshrink
6) Bolt to batteries


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## KiwiEV (Jul 26, 2007)

Another brilliant idea. I can get "heatshrink" free where I work which I might end up putting around the slices of bus-bar to stop dropped tools etc.
I don't actually know what the terminals look like on the batteries I'm going to use though so I'll do that near the end of the project.
I like the idea though. Very good.


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## moldiebrownie (Aug 29, 2007)

I pretty much followed Mike Brown's book "Convert it" except in a few minor areas such as using 1/16" copper strap interconnects between the batteries. I used 1/32" which is much harder to bend and I ended up having to use my vise. I did this because (and I could not find the Austin Album entry again) one pickup conversion guy stated that the 1/16" copper stap he used between his batteries seems warm/hot to his touch after a good run. This he stated indicated resistance and he expressed his desire to go to 1/32" strap. I was just doing my interconnects when I read this and decided to go ahead and go with this thicker copper stap. I always value what other people have done (not wanting to make the same mistakes myself) and went ahead and ordered online a long length of this copper which i sawed into bars myself. I have a laser thermometer but so far have not used it on the strap to see what temperature it is. I think I will do this next time I take my car out for a brisk run. I'll report later. Here is a pic of me cutting the bar I bought from Online Metals http://www.onlinemetals.com/ I bought a wide bar to cut myself because it was cheaper in this width. l cut it a little over 3/4 inch. Id avise anybody that buys this thickness to buy it cut in the width you want to use because even though I had a metal cutting bandsaw...it was a real bitch to cut! Weird because I thought copper would be easier than the 1/8" angle iron I had cut for the racks. 1/0 between the short interconnects is interesting to me. Is the consenses here that it would be adequate?


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## Adrian (Jul 26, 2007)

This EVDL post quoting Bill Dube' has a great explanation of how to select wire size. If the equations don't look right the original post can be seen here.

If your temperature rise/insulation is adequate, the only reason to use a larger wire would be to cut I^2R losses. In my case, switching from 1 x 1/16" bus bar to 2/0 for the interconnects would reduce heat loss a mere 300W @ 400 battery amps!

If 1/16" bus bar isn't adequate, you can always stack multiple layers, or switch to braided copper cable and use the water pipe clamping method. I'm not a fan of soldering large cable OR using copper water pipe. Solder can wick into the cable and make it brittle, and water pipe is an alloy with higher resistance than pure copper.

BTW, anyone have a good way of drilling clean holes through bus bars? A hand drill isn't the best, and my holes are rarely round


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## moldiebrownie (Aug 29, 2007)

Another thing about my battery interconnects. 1/32 copper strap is very rigid. I took my newly finished vehicle to a local car show...lots of hot rod guys but just six of us ev guys...*and we had all the people checking us out! *Anyway, a fellow ev'er pointed out that the interconnects should have some flex in them for when the batteries get jostled around on bumpy roads and such. He told me that eventually I will start to see leaks around the terminals...everyone seemed to agree with him and I do too. I want to go with braided strap eventually. In the front of my car...I have very good battery hold downs and I am not as worried about flex there as I am about the rear and center racks. Here is one of my front interconnects.


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## Mike D EV (Sep 11, 2007)

Copper is a difficult material to machine. The best way to drill a clean hole would be to drill a small hole first, and redrill it with progressively larger drills. The final hole size could be reamed instead of drilling for a perfect finish.
Clamping is pretty important as a standard drill will tend to grab at the flutes and screw into the hole, and try to pull out of the vice. WD40 as a drill lube will help a lot.
A Milling machine would be my method.

Is there a vendor for heavy Battery cables with the standard terminations?
Mike


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## iruraz (Sep 4, 2012)

Hi All,

I revive this topic instead of opening new one. Is there anyone to consider SAE J1127 standards for battery cables when choosing it?

Regards.


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## Tesseract (Sep 27, 2008)

iruraz said:


> ...
> I revive this topic instead of opening new one. Is there anyone to consider SAE J1127 standards for battery cables when choosing it?
> ...


You probably should have started a new topic, rather than dig up one that is 6 years old...

That said, J1127 typically applies to the 12V wiring in an ICE vehicle, not the traction pack wiring in an EV.

The more relevant SAE standard for EVs is J2289, but I'm pretty sure most people here don't bother with any of that stuff.


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## iruraz (Sep 4, 2012)

Tesseract said:


> You probably should have started a new topic, rather than dig up one that is 6 years old...
> 
> That said, J1127 typically applies to the 12V wiring in an ICE vehicle, not the traction pack wiring in an EV.
> 
> The more relevant SAE standard for EVs is J2289, but I'm pretty sure most people here don't bother with any of that stuff.


@Tesseract, you may be right about new topic. 

As you mentioned above people don't bother any of that stuff. But standards are important when you produce or convert vehicle as a "product". Generally people use welding cable. Is there any "control mechanism" for controlling electric vehicle structure and its safety?

Regards.


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## Tesseract (Sep 27, 2008)

iruraz said:


> ...
> As you mentioned above people don't bother any of that stuff. But standards are important when you produce or convert vehicle as a "product". Generally people use welding cable. Is there any "control mechanism" for controlling electric vehicle structure and its safety?
> ....


There are engineers that specialize in this sort of thing (called "compliance engineering", naturally) and I am not one of them, so I can only offer you general advice here (also, this site is for DIYers, not OEMs...).

In the EU you have to comply with two main directives/regulations: ECE R100 for safety and 2004/104/EC for electromagnetic compliance ("EMC").

Other directives/regulations may apply. I strongly suggest hiring a European compliance engineering & testing firm (such as, e.g., TUV) to help determine what you need to do. For example, all electronic sub-assemblies ("ESA") that are involved with steering, braking or the powertrain must be tested and certified for the much more stringent "e" mark, rather than the more common, and much more easier to obtain, "CE" mark.


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## iruraz (Sep 4, 2012)

Tesseract said:


> There are engineers that specialize in this sort of thing (called "compliance engineering", naturally) and I am not one of them, so I can only offer you general advice here (also, this site is for DIYers, not OEMs...).
> 
> In the EU you have to comply with two main directives/regulations: ECE R100 for safety and 2004/104/EC for electromagnetic compliance ("EMC").
> 
> Other directives/regulations may apply. I strongly suggest hiring a European compliance engineering & testing firm (such as, e.g., TUV) to help determine what you need to do. For example, all electronic sub-assemblies ("ESA") that are involved with steering, braking or the powertrain must be tested and certified for the much more stringent "e" mark, rather than the more common, and much more easier to obtain, "CE" mark.


@Tesseract thanks for your interest and informations. I only want to comply standards (EU or SAE) when I purchase products. And I try to find original EV equipments. And It is really hart to get in contact with OEM and to find their products (for example Delphi's product).

Regards.


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## JMac (Jul 10, 2013)

[h1]search for Kobalt 450-Amp Jump Starter[/h1]
Item #: 150923 | Model #: 102722 





16ft 2 strand 2 gauge for $30 can't beat this price anywhere.


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## major (Apr 4, 2008)

JMac said:


> search for Kobalt 450-Amp Jump Starter
> Item #: 150923 | Model #: 102722
> 
> 16ft 2 strand 2 gauge for $30 can't beat this price anywhere.


I would not use Jump Starter cable for any other than its intended purpose...jump starting. The search you suggests turns up 100's of hits.....all places where you can buy it, not any specifications. Jumper cables are notorious for having large diameter over the insulation and then tiny copper conductor inside. The insulation material is of unknown specifications w/r/t dielectric and temperature and life. Pay a few bucks more and get good quality cabling for your EV.


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## Caps18 (Jun 8, 2008)

http://www.mcmaster.com/#7818a15/=nkk5qi

This is the cable I am going to get. Probably along with a liquid tight conduit for both positive and negative cables.


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## Tesseract (Sep 27, 2008)

Caps18 said:


> http://www.mcmaster.com/#7818a15/=nkk5qi
> 
> This is the cable I am going to get. Probably along with a liquid tight conduit for both positive and negative cables.


McMaster-Carr is great for getting all the little mechanical doodads to do some mad prototyping, but not for welding cable... Shop around some more as you should be able to get 2/0 cable, in the recommended orange color even, for less than $5/ft. Standard black 2/0 welding cable should be less than $3/ft. Prices depend strongly on the cost of copper, of course.


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## njloof (Nov 21, 2011)

For example:

http://www.wireandcabletogo.com/Welding-Cable/


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## Old.DSMer (May 18, 2012)

I dealt with these guys - great group and fast shipping. AND, custom labelling.

http://www.trystar.com/

They also advertise as "coppercableman" on ebay.


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