balbs

For those who installed a 3rd party amp in the trunk. Where did you get the ground from? I don't want to run a straight connection to the battery. Is there a post or screw nearby that has good ground?

Thanks!

bruce_miranda

You should NEVER take ground from the battery.

Near the amp there are at least two ground posts, use one of them itself.

Anzafin

For example the same ground point what tail lights use.
Works for me!

- Antti -

inspire e60

I just took off my sound system but i had my ground near the the side wall of the battery's holding frame I just drilled a small hole, worked great there for me, since i didnt want wires going all over the place

Booyaazaa

You should find a flat metal chassis section next to the amp, remove the paint, and tap a screw into the metal with the ground. Keep the ground as short as possible and ground it to the chassis only.

balbs

Thanks for the suggestions guys! The ground point from the tail lights worked great for me.

umichchris

i used a bolt where there spare tire should be (M5s dont come with spares) but i agree with Bruce, dont connect it directly to the battery negative terminal...bad news bears.

MORI3L

Mines not connected directly to the negative terminal but rather to the opposite end where the battery would meet the chassis. Could you elaborate a bit more on why this is a really bad idea? I've had it like that for a while...don't want my car to explode tho...

methodsound

It will not explode, but it will not be able to measure the additional load you are putting on the charging system. The thing to avoid is connecting your ground cable directly to the negative battery post. There is a current sensor built into the negative battery post, it needs to see the current flow from all devises in the car. As long as your amplifier ground is connected on the car side of the current sensor ( not the battery side ) it will function correctly. I recommend using one of the star ground points provided other than the heavy duty one that the negative battery cable is using.

AI001

I don't agree with the theory of not putting it to ground due to IBS lead not being able to sense current drawn by the power hungry amp. IBS is on positive lead so as long as you connect directly to the positive irrespective of where you put ground you are bypassing it anyway. Remember in order to detect the "current" draw most electronic measuring device must be connected in series. IBS is intelligent I guess it checks both current and voltage to instruct dme to release alternator charge accordingly. For perfect solution read below

Putting it directly to the battery is still bad idea because there will be noise then due to difference in voltage between chassis and battery terminal directly, afterall your headunit is taking its ground from chassis somewhere. Difference in voltage will introduce noise.

After months and months of finding here is what I will suggest:

Buy these original BMW parts from dealer:

Double leaf connector - 61 13 8 377 733 (thicker one for 4-6mm cable) or 61 13 1370 692 (smaller one for upto 2.5mm cable) depending upon how much power your amplifier needs. If you need the crimped one the part number is 61 13 0 007 271 (thicker one with 6mm cable attached) 61 13 0 007 440 (smaller one with 2.5mm cable). I would recommend non-crimped one as anyway you need longer length of cable. Looks like part #02 or #05 as in this picture:



Fan connector - 61 13 1 387 144 1.5-2.5mm or 61 13 1 387 146 4-6mm for ground connection. Again choose size based upon your amplifier power usage. Looks like #05 in this picture



Really cheap parts (non-crimped ones) and then crimp (use plier or crimp tool if you have got) them to the cables, leaf connector to the positive side and fan connector to the negative side. Positive side should be inserted in the same pin row where Logic 7 and other power hungry electronics go from. WDS doesn't show exact name and location of plug but it is above the battery and pin has 5 pin (most of them empty depending upon installed equipments) and 2-3 of them should be empty, this is I am telling from my car which is LCI one, so make sure you find equivalent one for your car if pre-LCI. A indicative picture is here



Not very clear but it is around where fuse 60-71 arrow points to. There is only one row of double leaf pin (afaik) so should be hard to located. Take positive from there.

For negative insert fan connector as indicated in the picture #5 above into comb type connector as #1 covering and #2 contact located here indicated by X13795 or basically any similar ground point.



Now route your wire and you are done. Use thick gauge as appropriate and don't use the shit looking transparent cable which has less conductor and more cladding.

Hope it helps.

Regards,
Afsar