48v battery on a 2020 SQ5?

[Centaurik3]

Hi everyone. Has anyone heard of a 2020 SQ5 that has 2 batteries? One 48v and the other a 12v. The service person at my local Audi dealer says that I have two batteries in my 2020 SQ5. I've never heard of that. I took it in for stalling after start up, right when I go to accelerate, and then I get a low voltage warning. When I try to restart, I get a strong crank, but no start. Only when I add a battery jump pack the voltage goes from 10.4 to 13.x, and then it starts with no problem. They BOTH batteries test good. And they said they can't replicate it too. Thanks guys.

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[Smac770]

B9 SQ5 uses the CWGD engine, which has no MHEV aspect. The EA839 gas V6 used in the D5 and C8 are 48v MHEV. But the EA839 gas V6 (3.0T CWGD, 2.9T DECA) as used in the B9 are not MHEV.

The only 48v MHEV application on the B9 "platform" is the 3.0 TDI (diesel V6) used in the B9 facelift S4/S5/SQ5 in applicable markets where those get a diesel instead of a gas engine.

Your measured voltage should never be so low as 10.4v. You probably need to start by logging the battery voltage value and see what it is in fact doing, as measured at the battery by the J367, when you turn ignition on, then start the engine, then put the transmission in gear, then apply the accelerator pedal. But the voltage going low could be the chicken or the egg. Sorting that becomes your next task.

[Centaurik3]

Thank you so much for your input. I looked all over the internet and could only find basically what you said about the 3.0TDI. But the dealer tech is adamant about a 48V battery being in my SQ5, Non TDI. Thanks again for your help.

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[383vett]

Have him show you the 2 batteries.

[Hostile]

Have him show you the 2 batteries.

Yea, this.

[Smac770]

The MHEV battery sits in the spare battery well next to the primary starting battery, when equipped. So simple enough to look there.

The 48v battery in the SQ5 TDI you can see here to the right (side of vehicle) of the primary battery in this cutaway view: https://youtu.be/xZIwuI7EFzE?t=95

[Centaurik3]

Thanks again for the info. My car is still at the dealer, its been there since last Thursday. I'm going to ask to see this 48v battery and for them put it in their report, for reference. I wonder what they tell other customers that aren't as familiar with their own cars, I'm also a engineering technician in the aerospace field and I'm pretty familiar with ac/DC curcuitry and troubleshooting plus i have worked on cars myself for a few decades now. I know I don't know everything, but I'm an above average car person when it comes to troubleshooting. I appreciate your input, you seem way more knowledgeable than me. Thanks again.

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[Centaurik3]

Yes, when I pick up my car, I will be asking them to show me this extra battery.

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[Centaurik3]

Lol the dealer finally admitted, "umm...it looks like you don't have a 48V battery". They apologized and they still couldn't find out why my car stalls intermittently after start up. They said if it happens again, bring it right in

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[Centaurik3]

The tech working on my car explained that the altenators look very similar to the starter/generator alternator types used in the 48 volt systems. He was very nice and informative and apologized for the mix-up. He sounded like a good guy. So, no extra battery in a 2020 SQ5.

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[Smac770]

Still odd. There's never been a 48V B segment (A4/A5/Q5) vehicle in the United States. Maybe he normally works on the larger vehicles, where the twin scroll turbo 3.0T is 48V.

But still no joy on resolving your actual issue?

[Centaurik3]

Ok :( so my SQ5 is back at the dealer. I was on my way to work. about a mile from home, i was pulling away on a green light and then, it sputtered and then it stalled out. Right in the middle of a major intersection too. I tried to restart it, it had a strong crank, but no start. Then i was unable to get it into N, until i used that "L" shaped plastic tool placed in the floor board. I had to hold it turned while a police officer gently pushed me to a parking lot. While i was waiting for the tow truck, i was able to start it like nothing happened. Last time Audi had it for 3 weeks trying to duplicate the stalling, they never could and sent me on my way with a new battery. I really hope they find something this time.

[S4'ed]

Perhaps a problem with the Low Pressure Fuel Pump or it's Control Module?
Alternator cables/ground connection issues?
Battery cable issues?
Fuse box or Power distribution box connection issues?
"Terminal 15" or ECU relay issues?

Do you only have this problem when AutoStart is enabled?

Need DTC codes to begin troubleshooting this.

[Centaurik3]

Thanks for the ideas, I might have to do my own troubleshooting. I'm pretty good, but since it's under warranty, I'll let them for now.

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[Centaurik3]

Well, if anyone is interested, the dealer found a melted connection on the low-pressure fuel pump module. They also replaced the low-pressure fuel pump as well. They seem to think that's what was causing the intermittent stalling. They replaced the same fuel pump back in February because of the low pressure fault codes. We'll see, I suppose. I just hope it doesn't stall in the middle of a rush hour intersection like this past time.

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[Smac770]

These melted connections on the 3-phase pumps (introduced with B8.5) seem to be not as uncommon as one would hope.