Smart Alternators

[msh]

Originally Posted by theschmallfella

What?! I never knew this, and the battery in the A6 is being a ball ache for the last month or so, and I was thinking that it was nackered. So, are we saying that if I were to leave the A6 idling for 10 minutes on the drive it would charge the battery better than a long drive on the motorway? Am I picking this up right?

I don't know how and when does it charges the battery, but what I do know is that if you replace your battery in C6 or newer, and don't code it to charge controller, you'll sooner or later end up with battery being flat...

[John.]

Originally Posted by msh

I don't know how and when does it charges the battery, but what I do know is that if you replace your battery in C6 or newer, and don't code it to charge controller, you'll sooner or later end up with battery being flat...

.....sounds about right.

It's the devils work.....it really is.

[Ringmaster]

Originally Posted by SwallownAmazon

That explains why my E38 BMW 740 Sport has jump lead terminals under the bonnet when the battery is in the boot and not easy to get at. I'll start a thread on the 7 Series forum and find out some more as my alternator seems to be working overtime with the characteristic whistle as though it's working hard. That'll be a bugger if it ever goes wrong - it's buried deep in the front of the V of the engine as it's cooled by water at around 88 dec C. How hot can the bloody thing get ?!?

I don't believe that indicates your car has a smart alternator, it's more likely just a convenient feature to make jump starting easier when your battery is located in the rear. Besides, the E38 was made before smart alternators were prevalent, surely?

[theschmallfella]

Originally Posted by John.

No.

On the negative terminal* (if it has smart charging) there is a sensor which tells the ECU how many amps the battery is taking. Only if it is fully charged (and in good condition- the ECU will decide) and therefor taking very little charge, will the car be running solely off the battery.

The above is my take on it, TBH I'm not really worried about how it works just as long as it stays working!


*A cover on the negative terminal with picture showing not to attach a jump lead is a sign that it has smart charging.

I must check this tomorrow, if I can get into the boot. I tried earlier and it's frozen solid at the moment. The battery in the A6 is in the boot but I've not seen any warning notice about jump starting. The battery is running down if left idle for a few days, I thought maybe that it's just on the way out, not sure now. I did also think of something else, my sister had a 2001 A4 which developed an issue where the battery was constantly draining, even when a new battery was put in. I investigated it several times but couldn't find the source, the alternator was fine and even when I did find out a possible cause (apparently the alarm module fails and causes battery drain in the B6 and early TT's), removing the alarm module still didn't solve it. I haven't found any info online as to whether the C6 suffers any similar issues but it's got me thinking.

Sorry, I went off on a tangent there!

[SwallownAmazon]

Originally Posted by Ringmaster

I don't believe that indicates your car has a smart alternator, it's more likely just a convenient feature to make jump starting easier when your battery is located in the rear. Besides, the E38 was made before smart alternators were prevalent, surely?

Yes, it's only the latest 7 series cars that have that "luxury". My E38 does disconnect the alternator while starting and at full throttle though.