Smart Alternators

Ringmaster · 16-03-18, 11:23 AM

Peeps,

I was chatting to a mate of mine about an on-going problem he's been having with his battery. He's been told by his dealer (Alfa Romeo) that these new 'Smart' alternators only charge when there is no input from the accelerator. i.e., they only charge when idling or coasting, so there'is a strong possibility one's battery never gets well charged....

Has anyone else heard this?

vagdream · 16-03-18, 12:06 PM

I understood it was part of the fuel saving benefits of the 'coasting' mode of some current vehicles.

John. · 16-03-18, 12:38 PM

Been common-place for a while now.....if you're belting along at 70 mph with no extra consumables switched on....does the battery need charging, no.
Alternator will start charging it again when voltage drops below a prescribed amount.
Yet another ECU on the modern car

Colin Aitchison · 16-03-18, 03:06 PM

I had a 2008 BMW that only charged when coasting or braking, all to do with MPG saving.

Ringmaster · 16-03-18, 05:07 PM

Seems more of a threat to reliability

msh · 16-03-18, 08:42 PM

That's not alternator but charge controller, separate control unit that controls charging of the battery. Dunno which was first B series audi to have it, B6 or B7, in C series first was C6. It also requires that battery intended for that to be bough, with some specific code, which is used when adapting new battery to controller - if old battery will be replaced by new one without adaptation, controller won't charge it fully...

John. · 16-03-18, 09:01 PM

Quote:

Originally Posted by msh

That's not alternator but charge controller, separate control unit that controls charging of the battery. Dunno which was first B series audi to have it, B6 or B7, in C series first was C6. It also requires that battery intended for that to be bough, with some specific code, which is used when adapting new battery to controller - if old battery will be replaced by new one without adaptation, controller won't charge it fully...

As internal resistance of the battery increases with age the ECU will change the charging characteristics....... so yes the alternator ECU needs to know when a new battery has been fitted.

Makes me glad to drive the older stuff, better for the environment too

theschmallfella · 17-03-18, 12:50 AM

Quote:

Originally Posted by msh

That's not alternator but charge controller, separate control unit that controls charging of the battery. Dunno which was first B series audi to have it, B6 or B7, in C series first was C6. It also requires that battery intended for that to be bough, with some specific code, which is used when adapting new battery to controller - if old battery will be replaced by new one without adaptation, controller won't charge it fully...

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?

John. · 17-03-18, 06:49 AM

Quote:

Originally Posted by theschmallfella

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?

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.

SwallownAmazon · 17-03-18, 11:16 AM

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 ?!?

16-03-18, 12:06 PM	#2
vagdream Grown up member Join Date: Jul 2015 Location: Llandudno Junction Posts: 165	I understood it was part of the fuel saving benefits of the 'coasting' mode of some current vehicles.

16-03-18, 12:38 PM	#3
John. 4 ring whore! Classic Audi Club Member Join Date: Mar 2011 Location: Scottish Borders. Posts: 7,520	Been common-place for a while now.....if you're belting along at 70 mph with no extra consumables switched on....does the battery need charging, no. Alternator will start charging it again when voltage drops below a prescribed amount. Yet another ECU on the modern car

16-03-18, 03:06 PM	#4
Colin Aitchison Senior Member Classic Audi Club Member Join Date: Dec 2013 Location: Back home in Tillicoultry Posts: 1,308	I had a 2008 BMW that only charged when coasting or braking, all to do with MPG saving.

16-03-18, 05:07 PM	#5
Ringmaster Senior Member Classic Audi Club Member Join Date: Apr 2008 Posts: 1,326	Seems more of a threat to reliability

16-03-18, 08:42 PM	#6
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	That's not alternator but charge controller, separate control unit that controls charging of the battery. Dunno which was first B series audi to have it, B6 or B7, in C series first was C6. It also requires that battery intended for that to be bough, with some specific code, which is used when adapting new battery to controller - if old battery will be replaced by new one without adaptation, controller won't charge it fully...

17-03-18, 11:16 AM	#10
SwallownAmazon Grown up member Classic Audi Club Member Join Date: Jun 2017 Location: Tonbridge, Kent Posts: 511	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 ?!?