I'm looking to replace my 2009 Audi A4 2.0l TDi which I have owned for the last 13 years. I would like to replace it with another Audi approved A4 35 tfsi, but clearly over the last 13 yrs there has been a significant change in the technology. Firstly it now seems that you can no longer buy an A4 with a manual gearbox, unless you can find a good used 2020 model.

However, the main concern is that all the 2020 on A4's are now mild hybrid or MHEV's that use a separate 12v lithium ion battery, which raises a lot of concern, see attached photo which shows the lithium ion battery to the right of the std AGM battery encased in an aluminium enclosure. 

Firstly there is only a 3yr warranty on this battery, so clearly Audi themselves do not have any confidence as to it's long term life or use and if you were to purchase a 2020 model that warranty would have expired and therefore, like any battery it will deteriorate and could fail at any time beyond that time period with no cover.

The cost to replace the lithium ion battery, 4K0915101, is a current staggering £762 plus fitting and set up so possibly up to £1K? This is for a MHEV system that at best may save 5/10% on fuel so a quick calculation shows that potentially the replacement cost of this battery, certainly in my case, could be 2 to 3 the cost of any fuel saving, madness!

Is there anybody here who has any real time experience of these MHEV models and/or could enlighten as to the likely real time life of these 12v lithium ion batteries? A std AGM battery can usually last 8 to 10 yrs.

Further, can anybody advise as to what happens if/when this battery fails or it's charge falls to a level that it can no longer provide the necessary power? Will all the normal car functions still work and operate and what functions will/would be lost if the lithium ion battery is no longer operational? Could you in fact run without this battery?

Any advice would be greatly appreciated as none of the sales people or service manages I have spoken to have a clue.

Edited March 25, 20233 yr by Sprint

You're right to be worried. Someone local to me was in the paper last year when his mild hybrid mercedes e class battery went wrong and the bill.was more than the car was worth. 

Needless to say I won't be touching any of this electric nonsense in any form untill there is no other choice. 

Thanks for the reply. I think in the case of the Mercedes owner it was a full EV car and not just a mild hybrid. In his case it was £15K to replace the whole batteries, which was was more than the car was worth.

14 hours ago, Sprint said:

Thanks for the reply. I think in the case of the Mercedes owner it was a full EV car and not just a mild hybrid. In his case it was £15K to replace the whole batteries, which was was more than the car was worth.

That's the one, could have sworn it was hybrid as it was the old generation e class. Either way it is a huge worry. 

Are you buying new or would you consider used? 

Just checked, it was hybrid:

https://www.google.com/amp/s/www.leicestermercury.co.uk/news/leicester-news/mercedes-owner-horrified-new-battery-6545540.amp

Yes that is the one that I saw. On reading the full text it still remain unclear as to what sort of EV car it is, mild, plug in or full EV, but in any event a ridicules position and certainly an eye opener for all those pushing for full electric by 2030!

I am/was currently looking at a 2020 35tfsi because that seems to be the only year of the gen 5 A4's that have a manual gearbox.

I have had 3 A4's over the last 17yrs and would like to continue with one but it is looking increasingly likely that since they are all now MHEV's that I will have to look elsewhere which is really very disappointing. 

Whilst the cost to replace the MHEV 12v lithium ion battery is knowhere near the above example it is still a cost that I am concerned I will have to face at any time as there does not seem to be any information at to the longevity of these 12v lithium batteries, not what will happen when it fails.

What was the last year for non hybrid A4 models I wonder? 

 

I believe that the Gen 4 A4's were not MHEV's, mild hybrid, so that would make the last year these were manufactured would be 2018/2019? 

Mine was manufactured jan 19, registered in Aug 19. It’s a mild hybrid.

But is it a Gen 4 or Gen 5 model? The newer Gen 5 models started to arrive in 2019 so there was a period of crossover when they would both of been available and registered in 2019. I believe, but possibly wrong, that the mild hybrid started with the Gen 5 models?

Have you had any issues with your mild hybrid, particularly with the dedicated mild hybrid lithium ion battery or other issues associated with it being a mild hybrid?

Hi Sprint, 

We’ve only had it a month, but no issues. Being completely honest, I didn’t realise until after I’d bought it that it was hybrid. We sold our A6 C7 because it was too big but also because it was a diesel and in the two years we owned it, it did less than 9k miles. A recipe for dpf problems I think. Wonder if this battery is going to be the Achilles heel of the Petrol Audis. 
 

I’m pretty sure it’s a gen 5 mate, the grills low down on either side of the front have the Audi pre sense sensors mounted in them. 

Hi

I would suspect that it is a Gen 5 model. Do you have the rotary MMI control knob? If you do then it is a Gen 4 if you do not it is a Gen 5.

I think time is going to tell on these mild hybrid cars as to the longevity of the lithium battery?  

It’s got the rotary MMI control. 🙈

Then it must be a Gen 4 car. Was not aware that they were also mild hybrid?

On 3/28/2023 at 11:38 AM, CraigR1977 said:

Mine was manufactured jan 19, registered in Aug 19. It’s a mild hybrid.

My A4 Avant (B9) was registered in March 2019 and is a mild hybrid too.

On 3/28/2023 at 12:05 PM, Sprint said:

But is it a Gen 4 or Gen 5 model? The newer Gen 5 models started to arrive in 2019 so there was a period of crossover when they would both of been available and registered in 2019. I believe, but possibly wrong, that the mild hybrid started with the Gen 5 models?

Have you had any issues with your mild hybrid, particularly with the dedicated mild hybrid lithium ion battery or other issues associated with it being a mild hybrid?

My A4 Avant 40 TFSI was registered in March 2019 - it's a mild hybrid purchased used at 3,027 miles and bought from a main dealer (it was the service manager's car for around 4 months.) No problems with the lithium battery so far as I can tell, but I do need to replace the main battery. See my post on that subject.