1. Originally Posted by jimmylee
So . . . what did you do to make sure that the new cables wouldn't also become corroded like your old ones?
I don't think there is anyway to stop the internal corrosion. It's inevitable! Nothing last forever.

Dielectric grease on electrical contact points cuts down on corrosion on exposed connections.

But internally I don't think there's anything we can do.

2. Originally Posted by Pauls1150

Larger cable (smaller gauge number) will carry more current with less voltage loss; as current goes up, voltage drop goes up as the square of the current - NOT a one-to-one ratio.
Since Ohms law states that E = I x R it would seem that if you double the current (I) and keep the resistance (R) the same, the linear relationship would mean that the voltage drop (E) would double. Perhaps you were thinking about the power which would be P = I(squared) x R which would mean if the resistance was the same and the current doubled the Power (watts) would quadruple.

3. ## euromotoelectrics

Originally Posted by walt3022
I wouldn't be too swift to dismiss this as a scam. Old airheads typically have old cables. You can service the cable ends and miss the build up of corrosion under the cable insulation farther down the cable. Can it hurt to replace a cable that may be 30+ years old?
Having said that, I think the ebay offer cited above is quite high, but I have happily purchased new cables from www.euromotoelectrics.com. His site also gives a more detailed explanation as to why they are a reasonable proposition.
I went to euro's web site. Can't find their hours posted anywhere!! Called them on Saturday - guess what??

4. ## Cables

It is true, that corrosion is primarily caused by oxygen. So...preventing oxygen contact is the way to stop it! On new wires, using dielectric grease is the way to seal out the air and oxygen. On stranded wires, that have jacketing, one can get dielectric grease to "suck" in by using a hot air gun.

Ironically, all the talk about electric flow is somewhat nullified simply because in the completed circuit, the electric flow goes through aluminum! Remember, the negative ground cable actually connects to the transmission case. Aluminum is a notoriously poor conductor. I am not sure how much this affects the starting circuit, but it, at least, affects the conductivity of electric at the locations were wires are "grounded" to the engine/transmission case. This is why, there are problems with housing that still has some of the aluminum wiring that they used during wartime to save on copper/brass. All of those connections are now getting terribly corroded and actually causing house fires.

My very humble opinion, is to clean the wiring, re-solder when necessary, then thoroughly clean all connections where electric flow is crucial (like diode board/starting circuits, points/coil groundings, and then be sure to use dielectric grease at every point possible!

Expensive gimmicks are usually not needed, and only have a small percentage of improved performance, if any. Usually nothing noticeable!

Don't waste your money, but use your usually wasted free time, and put it to good use!

Your BMW will love you for it!

5. Thanks for the correction, Paladin, guess I was too quick to jump in on this...

6. The wheel is handy but when you throw power into it you need to watch carefully. The rest of your post was right on but the old teacher in me couldn't let the little error go.

7. Originally Posted by jimmylee
Aluminum is a notoriously poor conductor.
Actually Aluminum is a pretty good conductor (fourth best metal after silver, copper and gold) but corrodes very easily which drastically affects the conductivity of any mechanical joint in the circuit. If the connection points are kept clean and protected from contact with the air (in power wiring they use a substance called Penetrox) it will function almost as well as copper. Cleaning and protecting all grounding points on any vehicle that uses the chassis as the common for it's electrical circuits would be part of good maintenance practice especially if you live in a warm, humid environment (particularly near the ocean).

8. I'm hoping that someone will chime in with a source for quality battery wire so us hands-on guys (cheap) can make our own. I can find wire locally, but it's not the high strand count like the original.

Ed

9. It seems that an improvement in current carrying capacity by using a larger conductor as in this case would be based on the original cable having insufficient capacity to do the job while the replacement does.

Did the BMW engineers specify a cable that due to size & length was ill suited to the job?

Short of working on the starter or replacing the charging system who ever goes into the engine to test & clean the positive cable at the starter? Supposedly in the past, curmudgeonly airhead owners claimed to disconnect, clean & grease every connection on their bikes yearly or so. Seems a bit unlikely to me.

I am more surprised at the small size of the cable that connects the rest of the bike's electrical system at the same starter post.

10. ## Wire source?

I used to be a buyer at a large corporation and have purchased thousands of feet of wire. I would guess, though I am not sure, that any of the large electrical supply houses (I worked mostly with Rexel and Graybar) would have just about any wire you could want. The problem may be, though, that they will want you to by a minimum amount which may be a roll of a hundred feet. I know that our local Rexel outlet, will sell at the will-call counter and maybe you could get smaller lengths - and probably the connectors too.

They are located all over the US, so give a local one a call and find out.

11. Welding wire cable is sometimes used, as it is a high strand-count (for flexibility) with good current carrying capacity (amps!).... check welding supply stores. Stick with larger (4ga) and you should be just fine....

12. +1 on the welding cable. Your local NAPA guy can generally crimp cables which you can then solder over.

But why be so cheap? Any perfectionist knowns you could can get a tiny bit more conductivity from silver wire- its available if you want to spend the \$... smaller gauges actually used as speaker wire in some AV aps but hideously expensive.

13. Originally Posted by kentuvman
Do you buy in to this logic?
I can't tell you because I didn't bother reading all of that. And I certainly would not spend \$50 for cable I can make better for a fraction of that.

You want zero voltage drop across any cable. That means zero resistance, which isn't realistic.

So you take an acceptable voltage drop of 0.1V and divide it by 100A for a resistance of 1 milliohm for the length you need.

You can look up wire specs on any manufacturers site. Resistance is usually given for 1000 feet, so do some simple math to get it for 1 foot and go from there.

I made a ground cable for a local. Crimped the terminals and then flash soldered the ends where the cable stuck out. Resistance for a 13" cable was 0.000714 ohms (measured with an Agilent 33420A 4-wire meter).

Specs of the wire used:

Number: M22759/16-8
Gauge: 8 AWG
Stranding: 133/29
Diameter: 0.199 inch
Resistance @ 20??C per 1000 feet: 0.701 Ohms. (looks like that confirms my measurement at 1 foot = 0.0007 Ohms

Standard wall ethylene-tetrafluoroehtylene (ETFE) insulation ( also known as Tefzel ) designed for aerospace applications where weight, dimensional tolerance, and mechanical durability are required. This wire exhibits high chemical and radiation resistance.

14. Don't know the quality, but this looks like a good source for all kinds of wire and fittings.

http://www.riwire.com/

15. Originally Posted by edbmw
Don't know the quality, but this looks like a good source for all kinds of wire and fittings.

http://www.riwire.com/
This is a source for the classic car folks. Have not heard any thing bad about them.

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