[dragonsgate]

In another thread a member was asking some questions about what was needed to fix some things on his Ev. Some of us (self included) were quite adamant about sloppy wiring. One of the discrepancies pointed out was the stacking of wires. Wires should be progressively stacked with larger wire at bottom and smaller ones on top? Other than esthetics I am guessing it gives a better contact. How so? How about tapping into a lug?

[onegreenev]

Originally Posted by dragonsgate

In another thread a member was asking some questions about what was needed to fix some things on his Ev. Some of us (self included) were quite adamant about sloppy wiring. One of the discrepancies pointed out was the stacking of wires. Wires should be progressively stacked with larger wire at bottom and smaller ones on top? Other than esthetics I am guessing it gives a better contact. How so? How about tapping into a lug?

First photo is totally garbage and wrong. The second is good except I'd use a washer under the nut but not between the two connectors. Be sure the other connector is stout and not thin junk that will just squish out and break under a good torque. The last one looks usable but be sure you have a good connection. I don't think I'd do that but then again I never thought of that one. For a small connector it should be fine.

Remember to use good heat shrink on all connections. Don't use the crappy Auto parts store connections. I have them and don't like them I like hefty connections and good shrink wrap. My setup right now is mostly to get it all working. Then I will go through and clean it up. Working the kinks out at this time.

[major]

Originally Posted by dragonsgate

Wires should be progressively stacked with larger wire at bottom and smaller ones on top? Other than esthetics I am guessing it gives a better contact. How so?

Hi drag,

First realize where the current flows. It is not through the threaded stud or the nut. It flows from the lead base battery post into the cable lug. The stud and nut just provide clamping force to keep the base and lug in contact.

Each surface to surface contact is a source of resistance and potential failure due to corrosion, contamination and such. So you want the most current flowing through the least surface to surface contacts. That is why the big cable lug goes on the bottom so the "big" current doesn't have the extra contacts from the smaller cable lug.

How about tapping into a lug?

I've done this in a pinch. It isn't pretty and can have problems. I filed the surface flat before drilling and tapping. But even then, taps into copper are not very strong. Like I said----in a pinch. I used it for sense wires coming off Anderson lugs. So, not recommended, but if you have to, WTF

major

[Ziggythewiz]

I like to separate my high current wire from my low current wire(s) with a washer. The low current doesn't need much contact so it won't care if it's traveling through the washer to the next connector, and the high current wire will perform better with a properly sized washer to back it up.

The real contact surface area is just the portion of the contacts that touch under pressure from the nut/washer, not the full contact area.

[dragonsgate]

Thanks for the feedback. The tapped wire is to the Curtis battery monitor. It has been that way for many years now. I realize the steel bolt and nut is pretty useless for conducting current. That is one reason I put copper spacers inside the lug holes. Those that use the lug type cable ends have probably noticed the gap between the edge of the hole and the threaded post. It bothered me so I made some shims to fill the space around the steel post. I tried wrapping one continuous piece but find that concentric circles of copper works best. I do not know how close the straps on lithium batteries are but if there is noticeable space between the bolt and the hole in the strap maybe this could be a solution. By my way of thinking it gives a little bit more area for those electrodes to move around on. It also centers up the hole on the bolt making a snugger connection. This is also something that has been working for quite a while. Am I going to get flack for it? I think it was clever.

[PStechPaul]

That coil of copper tape is good for centering the lug if the hole is larger than the stud, but probably doesn't help carry any more current. You might be able to use copper that's a bit wider than the thickness of the lug and then torque it down to effectively make the contact surface of the lug larger, but it might be better to make a jig and use a press to do it right. High current connections need a clean, flat surface and lots of pressure well distributed over the contact area. And some sort of anti-corrosive compound will help keep the connection solid.

You can test a connection by running high current through it and reading the millivolt drop, or you can feel it to detect an abnormally high temperature, indicating high resistance and lost watts and less available amps. I like to use stainless steel bolts and other hardware because it does not corrode, has a high tensile strength for good compression force, and is non-magnetic. It's wise to use a thread compound to minimize galling and improve the compression for the same torque, due to lubrication and less friction. A torque wrench is a good idea.

[ricklearned]

I think I read somewhere that it is important to match the lug size and the bolt size. I have 8mm batteries, some 5/16 parts such as my fuse and some other 3/8 parts. I think I originally ordered 3/8 lugs but I am now going through and checking that the lugs are sized correctly. It is hard to fit a lug with a small hole on a large stud or bolt but putting a lug with a large hole on a smaller lug reduces the surface area. This is particularly true of the Tyco Kilovac contactor which has a small contact area on which the the lug sits.

[Ziggythewiz]

Yeah, ideally you would match all your cables to what they're connecting to. My kilovac conveniently came with some epoxy on the contact area to make sure I didn't have too much surface area.

[onegreenev]

This is also something that has been working for quite a while. Am I going to get flack for it? I think it was clever.

Actually after looking at the photo I think it is quite cleaver if you happen to have a lug that is larger in diameter than the post. It keeps it more or less centered and helps keep things from moving around. I'd say very little if any current will be passing through that spacer. Cleaver indeed, but it's still best to have the proper sized lug to post if you can. I happen to have a couple that are odd sized and could use that trick for a temp fix until I get the proper sized lug installed.