[JRP3]

I've been wondering how I should size the wiring on my project. 48 volt 400 amp Alltrax, I'll be using 4 gauge for the pack wiring, but what should I use for the switch to primary contactor, which will see 48 volts? Also what should I use for an ignition switch, will a 12 volt switch work?

[major]

Hi JRP3,

Wire size is determined by the current (amps) and the insulation by the voltage. Most insulation is good for 48 volts. Get up over 100 volts, you'd better check it.

You should have two basic circuits. The 48 volt, high current circuit which includes the battery, fuse, contactor, controller and motor. And a control circuit which may be 12 volts, 48 volts or a combination. This control circuit has the switches, contactor coil, and other low power devices. These are usually a lot less than 10 amps, mostly like 1 or 2 amps.

For the high current circuit, 4 gauge is probably o.k. although it is not rated for 400 amps. But it may be suitable for you average current. Depends on your duty cycle (how you drive) and battery (how long you drive).

For the control circuit wiring, I like to use all 18 gauge. It is probably overkill, but nothing wrong with that. I find smaller wire hard to work with and prefer just to stock a variety of colors of 18 AWG.

Hope this helps,

major

[frodus]

http://visforvoltage.org/forum/3111-...#comment-17335

that might help a bit...

its all about how much current you'll need to carry. 400A is likely peak... but your cruising current won't be more than 150-200A... so size the cable to that. See my post in the above thread.

[dataman19]

Isn't there also specific wire type (I'm talking about wire flexibility, temperature and abrasive resistance).
I know welding wire is cheap - but not the better choice.
..
I'm asking all the other members- Which Wire Tyupe do you recommend?
..
Then I have to ask: Which wire type is the best?
...
dataman19

[JRP3]

Welding cable seems to meet the requirements since they need to be flexible and abrasion resistant. They'll see more action on a welder than on an EV.
As an update to my original post, the 4 gauge was fine for the battery wiring, but does get a bit warm under heavy load on the controller to motor wiring.

[Sunking]

Ok I am a commercial electrical engineer and can help with wire strand type and insulation.

Starting with insulation from my POV you want to look at either MTW (machine tool wire) or DLO (diesel loco automotive). Both are synthetic rubber compounds which means flexible, and resistant to heat and oil. Properties you need in a EV. I am sure the automotive industry has very similar insulation types.

As for wire stranding the finer the better. Not because it carries more current, but because it is much easier to bend around tight quarters and vibration resistance. Wire Class H and I are the finer or higher strand counts. FWIW the finer strand counts require much higher degree of termination techniques and tooling.

[DIYguy]

Originally Posted by dataman19

Isn't there also specific wire type (I'm talking about wire flexibility, temperature and abrasive resistance).
I know welding wire is cheap - but not the better choice.
..
I'm asking all the other members- Which Wire Tyupe do you recommend?
..
Then I have to ask: Which wire type is the best?
...
dataman19

Welding cable really is the best for this application. Many small strands allows flexibility while overall cross sectional area provides current carrying capacity. The sheath on welding cable is very abrasion and oil resistant. Some sizes of welding cable come in a "Superflex" option,.. these ones have even more strands/flexibility. You likely don't need to go to Superflex... but if you had some, it would work fine.
For a 400 amp peak application with up to 200 amp draw for longer time periods, I would use 2/0 cable. It may be a bit oversize... but better that than under.

[JRP3]

Another point. The cable I used was marine cable from work. Not quite as flexible as welding cable but better than standard automotive cable. Boats, speed boats at least, see much higher vibrations and shock loads than cars, and I've never seen cable fatigue issues on a boat. I'd think that any welding cable would be more than good enough.

[Joey]

I'm at the point of selecting cable. I dug up this thread with a google search. The electrician at work recommends DLO cable. I looked into it. 4/0 AWG is rated for 405 amps, has good flexibility - min. bending radius is 3.1 inches, 550 strands of 24 AWG conductors, rated for 90 deg C, and the jacket has chemical resistance (PCE). The electrician is going to help me get it at the local supply house, which will include rental of the hydraulic crimping tool that they only loan out if you have an electrical license. Now the only drawback - as usual - price. I need to get a quote.

[Ziggythewiz]

You don't need 4/0. If you want you could use it for the motor controller loop, but you don't need it anwhere else. You want wire rated for your average use, not peak.