Car Stereo Headunit causing increased Battery Discharge

[orinj]

I've had a non-standard car stereo headunit (Alpine iDA-X100) that I fitted to my mark II Octavia over two years ago. In order to keep the memory and settings intact it has a permanent power feed (though not switched on) when the car is not being used.

Unfortunately, after a few low battery problems and not being able to start my car a couple of times these past few months I took the car in to my local dealer to check for any electrical problems. They told me that the battery was discharging 0.2W/h rather than the expected 0.02W/h because of the non-standard headunit.

Apparently the standard Symphony headunit 'speaks' to the on-board computer to check everything is ok when the car is not being used and because my headunit is not communicating with it, the computer keeps polling back and forth to try to get a response. This is causing the excess battery discharge.:thumbdwn:

Does anybody know if this can be stopped or prevented so that the battery isn't hammered so much?

Edited 28 March, 2009 by orinj

[Ali_Wright]

Thats an interesting point. I too have the same Alpine head unit fitted with the car permanent +12volts connected to both the permanent and switched supplies of the head unit.

I have also been caught out on two occasions after leaving the car for a week and coming back to a flat battery.

When I installed the unit I disabled the CANbus address for the standard unit using VAGCOM and this seemed to stop any faults which were being flagged up by the ECU trying to find the standard head unit. But the battery issue happened to me after that.

I'll put a meter in line with both lines into the Alpine and see how much current it pulls while switched on and off. There may be a need to run a switched live from the fusebox to prevent it

TBC............

[Ali_Wright]

Hi Orinj,

I've had chance to have a look and after the car is locked and has been allowed to go to sleep (2 minutes ish) the current drawn from the battery is approx 130 milliAmps. If you pull out fuse 8 in the fusebox next to the battery the current drops to 2 milliAmps (alarm etc)

Fuse 8 is the permanent 12 volts supply for the radio.

It appears that the Alpine iDA head unit pulls current even when it is switched off when it is connected to a permanent supply. If you switch the red "ignition" cable on the back of the unit then the unit "goes to sleep" and the current drawn reduces dramatically.

The solution is to route a switched 12 volts from the fusebox inside the car (located behind the end panel of the drivers side dashboard. If you fitted the headunit using the proper Skoda fascia adapter and wiring loom then it will have come with the cable and instructions on which spare fuse bay to use.

Once this is done swap the red and yellow cables on the rear of the head unit. This has to be done to ensure that the cars permanent 12 volt supply is connected to the correct connection on the unit.

After this has been completed the current drawn from the battery when the car is locked is again 2mAmps

Use VCDS (VAGCOM) to alter the CANBUS configuration so that it does not look for the original radio.

Happy days

[orinj]

Thanks for your investigation Ali. It's been a while since I installed the unit but I'm sure I came across this the first time round and may have cut corners in order to get the power correct.

From what I remember, I initially tried to get a switched power feed but couldn't have both a switched (ignition) and non-switched power feed. Since the non-switched feed was more important in order to preserve headunit settings I stuck with that, leaving me with a permanent live feed and hence draining battery.

I haven't used VAGCOM to alter the CANBUS configuration. Is this something I can ask my local Skoda dealer to do or should I ask one of the nice guys on this forum to help?

I'll take a look at the power feeds first and get them changed or re-wired before doing anything else.