MZ-3 Negative battery cable (from 4/99)

[Ron Stygar]

Trying to get the battery cable clamp part. The S54 negative battery cable doesn't come up on the EPC. I ordered the one for the S52 which turns out ito be the same. $$$.

<img src="http://www.unofficialbmw.com/images/batterycableneg.jpg">

[bob lindquist]

Trying to get the battery cable clamp part. The S54 negative battery cable doesn't come up on the EPC. I ordered the one for the S52 which turns out ito be the same. $$$.

http://www.unofficialbmw.com/images/batterycableneg.jpg
They dug real deep into the flesh with that price!

[///MDex]

Anything special about the BMW unit? I think I picked up one at my local AP store for ~$5

http://www.digitalsimple.com/TheMCoupeProject/FORWEB125-2533_IMG.jpg

http://www.digitalsimple.com/TheMCoupeProject/FORWEB125-2530_IMG.jpg

[Ron Stygar]

[QUOTE=///MDex]Anything special about the BMW unit? I think I picked up one at my local AP store for ~$5
QUOTE]
I know you can get a Pep Boy one for $5. I should have checked pricing before ordering, but I didn't. I also could have returned the one I got, but I didn't.
I was trying to get the unique clamp as a spare for both cables. The up to 4/99 M-Z3 cable retails for $18.70. Should have bought that one to see if it had the unique clamp. The from 4/99 retails for $71.75 which I paid $43.79 for.
The positive cable retails for $200.00.

[///MDex]

I was trying to get the unique clamp as a spare for both cables. Ah, I see. Do you have any idea though why the BMW units are so pricy? Something about the cabling used? The gauge?

Anyway, paying ~$45 for a ~$75 cable is a good deal :)

[Ron Stygar]

Ah, I see. Do you have any idea though why the BMW units are so pricy? Something about the cabling used? The gauge?

Both ends are crimped and soldered. The crimped inside lug diameter is 9 mm. Will check my book later today. Your pic post saved me a stop at Pep Boys.

[The Other Tom]

Do you have any idea though why the BMW units are so pricy?



My guess is that they don't get much call for them...low volume part, special order = high price.

[Ron Stygar]

Anything special about the BMW unit? I think I picked up one at my local AP store for ~$5

My cable measures .354 inch in diameter. Code book says 7 strand measures .332 inch which is 1 gauge. The BMW cable has around 400 strands. Have no idea which way how the number of strands changes the gauge. How many strands did the one you purchased have?

<img src="http://www.unofficialbmw.com/images/batterycableneg-1.jpg">

[dwm]

My cable measures .354 inch in diameter. Code book says 7 strand measures .332 inch which is 1 gauge. The BMW cable has around 400 strands. Have no idea which way how the number of strands changes the gauge. How many strands did the one you purchased have?

<img src="http://www.unofficialbmw.com/images/batterycableneg-1.jpg">

For battery cable replacements, I like welding cable. Very flexible. I have some 2/0 I bought from McMaster-Carr a while back for when I finish the new battery box. I think it's ~ 1300 strands. McMaster-Carr P/N 6948K96.

Pic of the ends is attached. Diameter of copper (not counting the jacket) is about .5"

[dwm]

A zoom of the end of the red one.

[Randy Forbes]

My cable measures .354 inch in diameter. Code book says 7 strand measures .332 inch which is 1 gauge. The BMW cable has around 400 strands. Have no idea which way how the number of strands changes the gauge. How many strands did the one you purchased have?

<img src="http://www.unofficialbmw.com/images/batterycableneg-1.jpg">

As I'm sure you know, the current travels down (around) the outside of the copper. I would presume the advantage of a greater number of finer strands (besides cable flexibility) is there would be fewer air voids that would enable localized hot spots.

Ron, you have a knack for asking questions about things that we just all take for granted. As dwm would say, "it makes you look up" :thumbup:

[Terry Kennedy]

For battery cable replacements, I like welding cable. Very flexible. I have some 2/0 I bought from McMaster-Carr a while back for when I finish the new battery box. I think it's ~ 1300 strands. McMaster-Carr P/N 6948K96.Yup. In 1977 I got fed up with the low quality of jumper cables then available (and in those days they still used copper!), so I bought some welding cable, alligator clips, and red/black boots and made my own. I've had them in the trunk of the 7 cars I've owned since then and they're now in my BMW. I amazed a friend last winter when he needed me to jump-start his car - he pulled out his sooper-dee-luxe import cables, and when he tried to unfold them, the insulation shattered and fell off. I pulled out my cables, flexible as ever, and got him going.

[dwm]

As I'm sure you know, the current travels down (around) the outside of the copper. I would presume the advantage of a greater number of finer strands (besides cable flexibility) is there would be fewer air voids that would enable localized hot spots.


'skin effect'. However, it isn't present for DC current (0 Hz).

[Randy Forbes]

'skin effect'. However, it isn't present for DC current (0 Hz).

I guess you know what most of my wiring was for :angel:

Seems as though the air void thing would still hold true though...

So now Ron has caused me to look up ;)

[dwm]

I guess you know what most of my wiring was for :angel:

Seems as though the air void thing would still hold true though...


The fill factor is more or less the same regardless of the number of conductors (with an infinitely thick bundle, it's exactly the same). They only differ for boundary conditions (in this case, the jacket). With smaller conductors (more strands/cross sectional area), you have more air voids of smaller volume each. With fewer conductors, you have fewer air voids of greater volume each. In either case, the fill factor for an ideal (infinite cross section) bundle of round conductors is pi/(2 * sqrt(3)). That's about .9.

A solid cable has greater DC conductivity than a stranded one. That's generally true up to frequencies well above what you'd find in a power application.

To the best of of my knowledge, the only reason for higher strand counts in DC or low-frequency AC apps (like below 10kHz for copper over short distances) is greater flexibility. Since the idealized fill factor for round strands is .9, you don't give up very much in DC current capacity. But it costs a lot more to make the higher strand count cables, so you pay for the flexibility.

[///MDex]

How many strands did the one you purchased have?Beats the BMW outta me; its 2 gauge (http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/wirega.html). My car starts - its a battery cable - end of my story.:)

[pmpntl]

[QUOTE=///MDex]Anything special about the BMW unit? I think I picked up one at my local AP store for ~$5
QUOTE]
I know you can get a Pep Boy one for $5. I should have checked pricing before ordering, but I didn't. I also could have returned the one I got, but I didn't.
I was trying to get the unique clamp as a spare for both cables. The up to 4/99 M-Z3 cable retails for $18.70. Should have bought that one to see if it had the unique clamp. The from 4/99 retails for $71.75 which I paid $43.79 for.
The positive cable retails for $200.00.

Ron, where did you get that cable for $44 bucks... my dealer wanted over $80... i broke the threaded part of that clamp off. Now, i'm using a monster cable (-) clamp and cut the top of the cable off.

[Pinecone]

The fill factor is more or less the same regardless of the number of conductors (with an infinitely thick bundle, it's exactly the same). They only differ for boundary conditions (in this case, the jacket). With smaller conductors (more strands/cross sectional area), you have more air voids of smaller volume each. With fewer conductors, you have fewer air voids of greater volume each. In either case, the fill factor for an ideal (infinite cross section) bundle of round conductors is pi/(2 * sqrt(3)). That's about .9.

A solid cable has greater DC conductivity than a stranded one. That's generally true up to frequencies well above what you'd find in a power application.

To the best of of my knowledge, the only reason for higher strand counts in DC or low-frequency AC apps (like below 10kHz for copper over short distances) is greater flexibility. Since the idealized fill factor for round strands is .9, you don't give up very much in DC current capacity. But it costs a lot more to make the higher strand count cables, so you pay for the flexibility.

And flexibility is also vibration resistance, so in things like cars, it becomes fairly important.

Copper work hardens under vibration, so the more strands, then less effected by individual strand breakage. One strand, it breaks, you walk. :)