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 Post subject: Re: 12 volt battery?
PostPosted: Mon Nov 30, 2020 7:41 am 
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Joined: Thu Nov 12, 2020 3:48 pm
Posts: 2
Thanks, very interesting that the 12 volt battery charging software seems quirky!

Well, 4 weeks after the service actions:
*service action 80C8 air conditioning software update; and
*service action 93H4 battery regulation control unit and low-voltage connection seal,

I have had a range of electrical problems. Have been using the 12 volt battery trickle charger, all tickety-boo there, but last week all of a sudden the high voltage battery wouldn`t charge. Red plug-in light in vehicle. External charging unit green and says plugged in and charging. Charging module on vehicle solid yellow. Return to dealer using charge maintain mode. Dealer says its the cord on the external unit. Resealed it and sent me home. Parked the vehicle for 3 days to de-Covid. Went for a 20km trip to use up the high voltage battery. Used the seat warmers. Returned home with 5 km showing on the high voltage battery.

On restart attempt, the same problem as on my initial return home after the recall service: yellow engine malfunction lamp continuously lit. Vehicle will not start, even in EV mode. After numerous attempts nothing. Tried the trick that worked last time, touching convenience key to sensor on steering column, this time nothing. Yellow engine malfunction light still on. Vehicle immobile. So frustrating. I`m guessing that there was something in the two service actions that caused a software or electrical glitch.

Back to the dealer, again.

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2018 A3 E-tron Technik Sport Tech


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 Post subject: Re: 12 volt battery?
PostPosted: Thu Apr 22, 2021 4:44 am 
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Joined: Thu Apr 22, 2021 4:21 am
Posts: 2
Very instructive reading about the A3 e-tron 12v battery. After 18 months of ownership of 2015 model I have just received the yellow Low Battery warning. After reading some forum material online I attached a 12v charger to the charging points in the engine compartment which then read 3 on a 5-point scale. I charged overnight alongside re-charging the high voltage batteries. In the morning it still read 3. When I removed the high voltage charger, however, the needle on the 12v charger moved steadily from 3 to 0. What can I deduce from this? I found the high voltage batteries had been fully-charged as normal, but a few seconds after starting the car up the Low Battery Electrical Fault Workshop warning re-appeared.

As I understand it, the Low Battery warning indicates either a 12v battery nearing the end of its life or a faulty DC converter. Can I tell from these symptoms which it might be? Does the shift from 3 to 0 indicate that the converter is working correctly and the 12v battery has been fully charged alongside the high voltage batteries? And therefore does the warning light indicate that despite being fully-charged the battery is no longer delivering adequate power and needs to be replaced?

Anyone know how to read the runes on this please?


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 Post subject: Re: 12 volt battery?
PostPosted: Thu Apr 29, 2021 6:21 am 
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Joined: Thu Apr 22, 2021 4:21 am
Posts: 2
Just to follow up my own post for anyone with same issue: the fault triggering the low 12v battery warning proved to be not the 12v battery itself but corrosion on the attached earth strap which in turn had reached the control unit located beneath it and adjacent to the battery. Replacing the earth cable and control unit, therefore, fixed the problem. This was done in an Audi workshop.


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 Post subject: Re: 12 volt battery?
PostPosted: Wed May 12, 2021 9:57 pm 
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Joined: Wed May 12, 2021 9:41 pm
Posts: 1
GolfCartDriver wrote:
New to the forum. Vehicle just 1 year in service only 1200 km (COVID a factor, working from home), 90% electric since just grocery shopping and errands in city, only 2 longer trips during the summer. Works exactly as I'd hoped - just like a glorified golf cart - easy on the planet and the pocket book. No cold weather (parked in heated garage), no lights left on overnight, no incidents, no fault or warning lights (in particular, no red or yellow battery lights), the combustion engine came on once at around 250 km even though high voltage battery fully charged - indicator said combustion engine needed to run.

Took to dealer for 15k/1 year maintenance, even though low km. Dealer also did:
*service action 80C8 air conditioning software update; and
*service action 93H4 battery regulation control unit and low-voltage connection seal.
No charge, happy as Larry, straight home.

Parked for 10 minutes. On attempted restart, yellow malfunction lamp continuously lit. Vehicle will not start, even in EV mode. After numerous attempts and even after waiting overnight, called roadside assistance who showed how to turn off yellow malfunction lamp by touching convenience key to sensor on steering column. Drove on EV to dealer. Dealer tested it and said 12 volt battery dead. It failed to charge overnight, so dealer says it requires new battery. C$807 plus tax. Warranty won't cover! Dealer alleges "improper usage" - not driving it enough! Dealer says you need to use gasoline engine! Huh, I thought that just driving the vehicle charges the 12 volt battery, but dealer says that it only charges when combustion engine is used.
Dealer also installed a trickle charger for another C$380 plus tax, so I can plug in the 12 volt battery once a week on household current to keep it topped up.

Can't find a schematic online, but thought I'd read that the high voltage battery charges the 12 volt battery through a connector module, and I've searched for an alternator for this vehicle in the US on https://parts.audiusa.com/ and can't even find one listed.

Is there an alternator or is the 12 volt battery powered by the high voltage battery?
Must I use the combustion engine? If so, what's a reasonable minimum?
Was there something in the service actions that triggered the problem?



That dealer is scamming you.

There is no need to use the gasoline engine, the 12V battery gets charged by the high voltage DC/DC converter any time the car is on. I know because I just went to the garage and tried it. It will also very likely get charged any time the car is plugged in, which means they sold you a trickle charger that you don't need.


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