[Ender]

I went and had my own look and it does exist!
At least on my '23 anyway.

It’s deceiving! It’s not actually connected. The most people seem to be able to do with it is pop the trunk, which is at least somewhat useful.

 

[gk1]

It’s deceiving! It’s not actually connected. The most people seem to be able to do with it is pop the trunk, which is at least somewhat useful.

Right, it does seem to imply that it is just to release the trunk and not for charging.
But then with access to the hood there are posts under the hood to charge. So that's all you should need. (Your case seems to be special unfortunately. )

Edit: Oh unless you meant for a 12v charge point all-the-time....yeah...this is just for the "supposedly rare" case that the 12v battery dies.

Interestingly they do explicitly warn NOT to try to jump start anyone else.

 

[Ender]

Yeah, people can get the trunk open but not the hood. People have said it’s disconnected and others have said it’s because the Taycan has a frunk button on the remote that the GT doesn’t have.

For jump starting, the battery is very small, 40 amp hours is about the size of a lawnmower. I can see an ICE car sucking up the entire battery and maybe still not being able to start.

 

[gk1]

Yeah, people can get the trunk open but not the hood. People have said it’s disconnected and others have said it’s because the Taycan has a frunk button on the remote that the GT doesn’t have.

Wait, what?
I just thought we were using "trunk" to mean frunk (hood) since that is what we were talking about.
The image is specifically for the frunk. That is definitely what it does.
The rear trunk is easy just climb through the fold down seats and pull the emergency release. Plus nothing in the actual rear trunk of any use in a dead 12v situation anyway.

 

[Ender]

Wait, what?
I just thought we were using "trunk" to mean frunk (hood) since that is what we were talking about.
The image is specifically for the frunk. That is definitely what it does.
The rear trunk is easy just climb through the fold down seats and pull the emergency release. Plus nothing in the actual rear trunk of any use in a dead 12v situation anyway.

Oh yes! The method to open the hood doesn’t work in the states. Dealers were opening up belly pans and going under previous to unscrewing the hood latch entirely.

 

[Ender]

An update for anyone following along: the car has been in the shop for 11 days now. They ended up having to call in Audi tech support and were given a battery of tests to run through. It was determined that the issue is the front and rear drive control modules need to be replaced. They managed to get the last ones in the country, which will take anywhere from 3-10 days to arrive and a few days to replace.

I'm unclear how this is related to the 12v battery (unless the modeules were running it down) or how confident they are that this will remedy the issue. In any case, I will be asking AFS for a lease credit and will strongly consider pursuing a lemon if this doesn't fix it.

My car has now been at the dealer since January 2nd and supposedly will be ready for pickup today or tomorrow. The repair has taken a long time because it required them to completely drop both motors from the vehicle. The drive control modules are not just small computers and also act as a three phase inverter. This was also their first time doing a repair of this type and there is supposedly one more to do right after mine.

At this point I am qualified for a lemon, but do not plan to pursue it unless future issues occur. I plan to also contact Audi for credits once I have a repair order to show them.

 

[Snorlax]

glad you are nearing the end of this!

did they have to drop the motors just to access the 12v for replacement? or for some other reason?

 

[Ender]

glad you are nearing the end of this!

did they have to drop the motors just to access the 12v for replacement? or for some other reason?

The drive control modules are in a place inaccessible before dropping the motors. I'm still unclear on how it related to the 12v being dead aside from maybe the control modules not sending power to it.

 

[zytra]

It’s deceiving! It’s not actually connected. The most people seem to be able to do with it is pop the trunk, which is at least somewhat useful.

Yeah, people can get the trunk open but not the hood. People have said it’s disconnected and others have said it’s because the Taycan has a frunk button on the remote that the GT doesn’t have.

For jump starting, the battery is very small, 40 amp hours is about the size of a lawnmower. I can see an ICE car sucking up the entire battery and maybe still not being able to start.

happened to me today, the car had not been driven for several weeks.
found my way inside with the key, then googled and found the trick for the taycan which got me to open the trunk.
went to harbor freight to get air shims and got in.
battery was at a dead 0.0V
jumped the battery with another 12V battery for a few minutes. note that after a few seconds the voltage was high enough and activated the systems, lights, horn, etc.
Removed the jump battery and the etron battery was sitting at 1.6V which is expected from a quick 5mn jump.
Plugged in a maintainer and it's been charging for about 1hour.

I hope the issue didn't trigger any drive issue like it did for you, I'm sorry this must have been a nightmare.

Has the issue popped up again?

I can understand failure and problems, however I am bit disappointed by the fact you have to rely on air shim to force your way into the hood. That's just crazy to me and screaming design fault. Seems like an easy fix which could have been implemented for at least 3 years and if not, at least officially documented.

 

[Ender]

Has the issue popped up again?

No, it has been good since. I was hit with the battery recall though and will need to get at least some of the cells replaced at some point. For now, I am just not supposed to charge over 80% until they can do the work.

I'm glad you solved your issue and it wasn't more than the dead 12v that all EVs seem to have issues with.

That's just crazy to me and screaming design fault

What's odd to me about this one is that it's something that Porsche had accounted for and Audi decided to remove the failsafe.

 

[zytra]

turns out the charger stopped charging and the battery emptied itself in the span of a couple hours.
I'll get in touch with the dealer, roadside assistance is of no help and the car is parked in my garage and there is no way a tow truck can get it out of there easily. so hopefully they can deploy a tech to replace the battery on site.

 

[Ender]

If you have a roadside tech hook up a jumper you can put the car in neutral so it can be pulled on to a flatbed. This is what we did with mine. Just have to remember you need a way to unlock the hood to get the car off the flatbed. My driver just closed the hood without knowing the headache it would cause.

 

[gk1]

What 12v charger did you use?

Also let us know what they end up charging you for the battery. I believe it retails for $1200

 

[zytra]

the charger i was using was a regular battery charger/maintainer designed for acid batteries. so when I realized it was a lifepo4 battery I figured that might have been the problem. at 12.8V charge rate it is a very low soc.

turns out I have a good regulated DC PSU, so I set it to 14.4V and charged it this way. It was current hungry for the first part and was c.c.'ing at around 20A (and 13.3V). to be safe I adjusted the max current to 15A, and it eventually charged it to full (14.4V). I read that some chargers push 14.4 and some others 14.6 / 14.8. I played it safe with 14.4.

I disconnected everything and it's been 30mn and the voltage is holding.


I read contradicting report on whether or lifepo4 batteries can handle full discharge like this one but figured it's worth a try.

No idea why their batteries are so expensive but that's not entirely surprising based on the costs of audi replacement parts in general.

 

[gk1]

I assume you tripped the BMS relay.

If the voltage drops below 10V, the relay is opened to protect the lithium ion cells.
Deep discharge (deep discharge protection)

(The relay is closed again as soon as the voltage remains within the range of 11 V < U < 14.8 V for 10 to 30 seconds. There is an audible click. The battery should then be charged for at least 30 minutes.)

If the voltage drops below 8.0V the relay can no longer be closed. The battery must be replaced.

Did you hear the click of the relay closing?

 

[zytra]

I assume you tripped the BMS relay.

Did you hear the click of the relay closing?

I heard some clicks, at least the one when I jumped the battery and the system saw > 11V.

Before going to bed last night the PSU was at 14.4V and 0.1A, so it was done charging and I pulled the leads off.
Checked this morning and the battery is still sitting slightly above 14V, which is about 96%.
I'll check again tonight then go on a ride and check again.

 

[Ender]

Glad you got it figured out and definitely a good idea to check after a ride to make sure that the power regulator is functioning (that was ultimately my issue).

 

[Internet Rando]

I read contradicting report on whether or lifepo4 batteries can handle full discharge like this one

The battery chemistry cannot deal with being flat, it totally destroys the battery. Having built battery packs from scratch from raw cells and electronics in a past life, I know from experience!
Because of this, any "battery" that you actually buy (and comes in a package, rather than raw cells) has a small battery management system built-in, which will disconnect the outside if the battery gets towards a dangerously low state of charge. This is why you read 0.0V -- it's entirely disconnected.
However, there is a diode in the BMS (probably actually a body diode from a MOSFET) that allows current to go in, even when it's cut off, so you can charge it up again.
The BMS also should shut off in case of over-voltage, or over-current.

The max state of charge for a LiFePO3 is 14.8 Volts. However, you need to also keep charging at that voltage for a while to fill it up -- it comes to top voltage before it's saturated. You should stop charging when the current draw gets low (like 0.1 Amps) at the full voltage (14.8V)
Note that if you charge below the max voltage, you won't ever get it to full charge.
Separately, the voltage is NOT a great indicator of state of charge, especially when not under load. The curve quickly flattens out, and then once the battery runs out, the voltage suddenly starts dropping quickly, at which point the BMS must cut it off to avoid damage.

Likely the reason we shouldn't jump another vehicle with this battery is that the BMS isn't beefy enough for the starter current draw. 40 Ah should be plenty to start an engine ... once. But, it'll probably draw 200 Amps or more, which might count as "overcurrent" for the BMS, and it would emergency break the cicuit. (Guessing here, but that's how it usually works.)

Overall, a LiFePO3 with proper BMS and proper access is a much better battery than a lead-acid battery. Although charging $1200 for 40 Ah at 12.8V is unconscionable. That's about a 10x mark-up!

 

[Ender]

which might count as "overcurrent" for the BMS, and it would emergency break the cicuit.

That's exactly what they have stated. They are worried about overcurrent causing damage to the battery and gases escaping.

 

[zytra]

The battery chemistry cannot deal with being flat, it totally destroys the battery. Having built battery packs from scratch from raw cells and electronics in a past life, I know from experience!
Because of this, any "battery" that you actually buy (and comes in a package, rather than raw cells) has a small battery management system built-in, which will disconnect the outside if the battery gets towards a dangerously low state of charge. This is why you read 0.0V -- it's entirely disconnected.
However, there is a diode in the BMS (probably actually a body diode from a MOSFET) that allows current to go in, even when it's cut off, so you can charge it up again.
The BMS also should shut off in case of over-voltage, or over-current.

The max state of charge for a LiFePO3 is 14.8 Volts. However, you need to also keep charging at that voltage for a while to fill it up -- it comes to top voltage before it's saturated. You should stop charging when the current draw gets low (like 0.1 Amps) at the full voltage (14.8V)
Note that if you charge below the max voltage, you won't ever get it to full charge.
Separately, the voltage is NOT a great indicator of state of charge, especially when not under load. The curve quickly flattens out, and then once the battery runs out, the voltage suddenly starts dropping quickly, at which point the BMS must cut it off to avoid damage.

Likely the reason we shouldn't jump another vehicle with this battery is that the BMS isn't beefy enough for the starter current draw. 40 Ah should be plenty to start an engine ... once. But, it'll probably draw 200 Amps or more, which might count as "overcurrent" for the BMS, and it would emergency break the cicuit. (Guessing here, but that's how it usually works.)

Overall, a LiFePO3 with proper BMS and proper access is a much better battery than a lead-acid battery. Although charging $1200 for 40 Ah at 12.8V is unconscionable. That's about a 10x mark-up!

that's really info, thank you. I wasn't exactly sure since I just did a quick good search, hence why I played it safe at 14.4V.
it's good to know the BMS is protecting the battery. I did see voltages much lower than 11V: 1.2V-1.1V, which is kind of strange. measuring voltage in the dark while probing the circular studs wasn't exactly easy, so maybe measurement error.