12 volt battery?

[Kmoores77]

Perhaps I’ve missed it somewhere but is there an actual traditional 12 volt car battery in the A3 e-torn? Some online info I’ve seen says it’s in the trunk near the gas tank but looking in my new (to me) 2017 I can’t find it. I’ve seen info on the jump start procedure under the hood but that uses non-battery terminals.

 

[Deepbank]

Hi Kmoores77,
Yes, the 12 volt battery is beneath a black cover plate in the trunk to the left of the fuel tank. The location is shown in the figure below.
Overview of Battery Location

 

[Kmoores77]

Thanks, Deepbank,

I don't think they mention that in the user manual, in fact, looking at the vehicle battery section again I think they are specifically choosing not to: "Because of the complex power supply, all work on the batteries such as disconnecting, replacing, etc. should only be performed by an authorized Audi dealer or authorized Audi Service Facility."

I guess that makes sense, this is not my 2007 A3 anymore... looking at its old manual in the same place they just say "All work on the battery requires technical knowledge!" before they tell you where it is.

 

[AvH]

If the 12V battery fails, or get disconnected, everything fails: can't open doors with fob, no dashboard, everything completely dead (as one can expect with a bad/dead/disconnected battery). The battery gets charged from the high voltage battery system via module A19. Charging also will no longer work if the 12V battery is dead.

I was able to make the car drive by hooking up one of these starter battery kits, on the points mentioned in the manual. It only drew 2.3A.

Note: this issue happened right after the car had a service visit at the Audi dealer. It was also an intermittent issue: one moment all was fine, the next it was dead. So in hindsight I think the terminal to the 12V was not tightened. Took it back to Audi, they stated they replaced the battery ($200 at Audi) and charged $300 in labor etc. So $500 for a battery... Maybe they just tightened the clamp again.

I am posting this in case others encounter this "dead car" issue - and maybe save the expense.

I initially thought the car did not have any 12V battery - that the 12V was always coming from the high voltage battery DC DC converter. The included Audi etron manual does mention a 12V battery in the front of the car (right side, near windscreen, under cover) - but it is not there in the etron, I suspect that is the location in a regular A3. So now know the 12V battery is well hidden in the rear trunk.

 

[cat]

I have, sadly, discovered the dead battery issue for myself. Seems I inadvertently left the sidelights on while the car was parked in my garage for a few days - am not going out in it very much at the moment what with the Covid-19 situation. This resulted in the battery - and hence the car - being completely dead on Sunday; I had roadside assistance out to it on Monday and they managed to start it, advised me to leave it on for 90 mins and then take it for a drive, which I did, then when I got back, and stopped it, pressed Start again and after an exciting array of error messages and the dash lighting up like a Christmas tree for about 30 secs, it went completely dark and dead again.
So, had roadside assistance out again yesterday and they got it started again, advising that the battery was likely beyond redemption and to take it to a dealer. IT's having the battery replaced - not under warranty, as the car has snitched on me and told them I left the sidelights on - at a cost of nearly £400. Ouch.

 

[cmc]

Hello all, I am new to this car, just picked up a 2018 a couple of weeks ago. Glad to have found this forum. First of all thanks for all the info regarding the 12V battery. I have several other regular cars and I have had great success keeping their 12V batteries alive for long periods of time by keeping them topped up. Lead acid it seems, like to be full, unlike lithium ion. I still have the original lead acid in one of my cars from 1997! Anyway with regards to the A3 I have plugged in my regular 1A trickle charger into the jump start terminals a couple of times. I am finding that the 12V drains quite a bit in terms of how long my 1A charger takes to get it back up to full. (In comparison to my other cars). I recently went on a fairly long trip, over 100 miles round trip. After topping up the high voltage I plugged in my 1A trickle and found that it was still rather depleted, taking several hours to top up..... Anyway interested to see if anybody else have paid any mind to the 12V..... :mrgreen: :mrgreen:

 

[bruuster]

I had same issue in Jan, with my 2017 bought used (lease return). Still under warranty though so dealer replaced for no charge.

On another topic, Just this month dealer said there was pre-paid maintenance and did the 40K mile service (engine oil, air filter, cabin filter, spark plugs, transmission drain and filter) for no cost. Who leases a new vehicle and buys the service package??

 

[cmc]

https://www.youtube.com/watch?v=QN1zXNpDbE0

DIY 12V battery replacement as well as VCDS coding.

 

[GolfCartDriver]

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?

 

[cmc]

Hi I have a 2018 as well and I purchased a voltmeter that plugs in into the 12V socket to observe things

- My car has a AGM 12V battery, I believe others may not.
- AGM battery has a different charging algorithm compared to regular
- There are 3 voltages that I see:
- 14.9/15V "full power"
- 13.4 "half power"
- 12.4 "not charging"

- Most of the time the system does not charge the 12V, I see it at 12.4
- When I use the seat heater it charges at the max rate of 14.9V
- When the 12V gets weak (without seat heater) charging will kick in at half power (13.4V)

The above I observe regardless of whether the gas engine is running or not.. The 12V charging algorithm seems to be biased towards maximizing mpgs and electric range at the expense of the 12V battery. I am now using seat heating more because turning on seat heating has the side effect of charging the 12V at full power. I'm not OCD on battery range or mpgs. A $500 bill for 12V battery replacement is much more expensive than losing a few miles here and there on gasoline or kilowatts...

- The 2018 model has higher mpg rating than older ones. I am guessing that the AGM battery and the lack of charging is the difference...
- I have a 240V system at home and can recharge in 2 hrs.. I don't think 2 hrs is enough to recharge the 12V adequately
- When plugged in, I see the "half power" voltage of 13.4 on the 12V side
- I have a 2A AGM smart charger which I plug in into the fuse box 12V terminal after charging the high voltage battery. It takes hours each time before the 12V is fully charged... I let it charge overnight.
- Perhaps if one charges at 110V and it takes 8 hrs, the 12V could be adequately charged?
- There is no alternator, the 12V is normally charged by the main battery but in a very controlled (and stingy) way.

Hilarious, keeping the 12V alive takes more effort than the main high voltage battery!

 

[GolfCartDriver]

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.

 

[JohnH]

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?

 

[JohnH]

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.

 

[danielblnc]

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.