Grounding question

[jjwithers]

Just curious if grounding a battery cable to the frame instead of the transmission will still work.

Or is it necessary that it gets grounded on the transmission (near the speedo cable)?

I'm thinking of grounding either to the frame or to the left side of the transmission to the bolt that mounts the transmission to the engine (near the shifter).

Before any criticisms ensue, keep in mind that it is a customized BMW project and the battery is being relocated. I am trying to tidy up the cabling as much as possible.

Thanks in advance!

-J

[SteveD]

Can't speak for the frame, but due to the fragile thread at the speedo/trannie ground, it's apparently a common mod to take the ground to elsewhere on the trannie.

[chasbmw]

The engine block is the place where the starter motor and other parts of the bike ground. I think that you might be better served by running an extra ground wire from the alternator/diode box via the grounding point on the coils, down to the negative post on the battery. You then just have to remember to disconnect the battery at the battery rather than at the gearbox. This is the fix proposed by rob Frankham.

Bikes with black painted timing chests often had grounding problems, because the paint got in the way of the ground path from the alternator diodes. BMW supplied a grounding lead that went from the diodes to the starter bracket, what Rob has proposed is just an extension of that ground path.

Cleaning up connections and providing a decent ground will increase the charging rate of your system

[jjwithers]

Thanks.
I guess my other question is how thin of a gauge wire can the negative battery wire get? Or is it a 'bigger is better' situation?

I have some welding cable that is about 1/4 inch to almost a half inch thick that I could use but again, I am trying to minimize my wiring so I prefer the look of something smaller.

[dougie]

I used #4 welding cable. Better than stock, and the size allowed me to re-use the original end terminals.
(and solder is better than crimped.)

[Motorhead]

if you use a 10 guage wire the operation will build heat, heat builds load, a thicker in gage will releve load and heat

thin weld lead with a thin core an solder is right track thinking

[Ken in Oklahoma]

Let me 4th or 5th that. #4 gauge welding cable is the stuff to use. The cable is intended for welding "leads", such as connection with the stinger of an arc welder. It is very flexible and has a real rubber jacket. The down side is that the cable is spendy, but you are getting value for your money.

I prefer to use new terminals rather than trying to re-use the old ones. I crimp them and then solder too, and cover the bare area with some shrink tubing. It makes everything look more professional.

There is a down side to new terminals. All I have been able to find are copper ones. Copper is great, except that it is soft and the terminal ends can become ugly looking since the terminal is more flexible than the cable itself. I hope someday to find a source for plated steel terminals.

Crimping the new terminals can be a bit problematic if you don't have a crimper that large, and who does? I made a crimper by boring a hole of the right diameter into some hardwood. Then I cut slightly less than half of the hole away. The actual crimping was done with the barrel of the terminal laid in the half circle and the use of a purposefully dulled chisel and hammer. If you do solder the crimp be careful not to wick the solder up underneath the cable jacket. It's too easy to do, and there's no way to see how the wicking is progressing. In this case less heating is more. If the crimp was good the solder is extra insurance. That is corrosion can't creep between the terminal barrel and the copper wire. Perhaps the welding shop where you buy the cable can crimp the terminals for you.

Ken

[Duane Ausherman]

Ken is right, don't let the solder wick up under the insulation if you can. Be sure to use heat shrink on the connection to keep the humidity out of the cable.

Ken, do you mean 4 gauge, or 4/0? I would try to find 2 or 4 gauge flexible stuff such as welding cable. I make up jumper cables from the free 2/0 and 4/0 I get out of cell sites for free. Makes for super quality jumpers.

A couple of years ago I needed the clamps and could only get a package of several sets from eBay. I made up more jumpers and gave the excess away to friends. I stil get compliments from them after they finally need them and find just how superior they are over the crap that one finds in auto parts stores. They are super heavy duty and just plain heavy. I keep a set in each vehicle.

[Ken in Oklahoma]

Ken, do you mean 4 gauge, or 4/0? I would try to find 2 or 4 gauge flexible stuff such as welding cable. I make up jumper cables from the free 2/0 and 4/0 I get out of cell sites for free. Makes for super quality jumpers.

Duane, you're asking me what I meant? I don't know the numerical designation, but it's somewhat larger in diameter than the stock BMW cables--and a lot more flexible. And it doesn't have that damned PVC jacket.



Ken

[Ken in Oklahoma]

Ken, do you mean 4 gauge, or 4/0? I would try to find 2 or 4 gauge flexible stuff such as welding cable. I make up jumper cables from the free 2/0 and 4/0 I get out of cell sites for free. Makes for super quality jumpers.

Duane, you're asking me what I meant?

I don't know the numerical designation, but there's a "4" in it somewhere. It's somewhat larger in diameter than the stock BMW cables--and a lot more flexible. And it doesn't have that damned PVC jacket.



Ken