Alternator whine after relocating battery to boot

[_XR6T]

Hi Guys,

 

Hoping to get some ideas on how to fix alternator whine after relocating the battery to boot. The whine only occurs when accelerating and higher RPM means louder whine. The whine is only noticeable when the battery is in the boot. If I relocate the battery back to the factory position there is no whine. The car runs fine with no apparent issues apart from the whine which gets annoying.

 

To relocate the battery, positive lead is a 0 gauge cable ran down the drivers side to the starter motor. Negative lead is 0 gauge next to the battery box. Ground point has been sanded back and have also tried new ground point.

 

Previous owner fitted the car with an aftermarket Alpine system with all speakers going back to the amp. There are 2 amps situated behind the rear seats. Amp positive lead is 2 gauge running down the drivers side to the factory battery point. Negative looks to be 4 gauge with the ground point being under the rear seats. Both amps have the same ground point which I have sanded. Speaker wiring also runs down the drivers side.

 

I have disconnected the amp by disconnecting the positive and negative leads, this made no difference to the whine which I would have thought means 1) the amp is not the issue, and 2) the 0 gauge positive lead from the battery to the starter motor running down the same path as speaker cables is not causing interference?

I have also wrapped the battery positive lead in aluminium foil as I thought this may help reduce interference if any.

 

Head unit is situated below the factory unit. When disconnecting the amp, the head unit remains on. The Alpine head unit has a remote control which I can control the power (turn on/off). Turning off the head unit makes no different to the whine. Seen some cases of the head unit causing the issue but unsure if related in this instance?

 

My next steps were to run the positive battery lead outside the car away from any speaker cables to cross off the possibility of interference. However, after that I am a bit stuck.

 

Any ideas before I leave the battery in the factory position and get an under battery intake?

[k31th]

I'd be doing your suggestion, e.g. run the battery relocation cable somewhere obviously out of interference range, just to confirm the interference is somewhere along the relocation cable.

[_XR6T]

Ran the positive lead outside the car and there was no whine, so definitely interference.

 

Also tried running the positive lead along the passenger side. Passenger side did have speaker cable for the front left speakers in addition to other factory cables. Disconnected the passenger side speakers from the amp and still had whine.

 

I could run the lead below the car but I was hoping to avoid this.

 

Has anyone used braided cable shielding sleeve applied to the positive lead to overcome interference issues?