Does your Macan EV keep SoC stable when left idle for a week or longer?

[dimaa_6abc]

Mine was updated in early May 2025, since then it was updated sometime in October, especially high voltage battery was updated, and I indeed see at least one change - before, the car would not stop the AC charging session when target SoC is reached, after the update it terminated the session as the other EV would. And currently I don't have SoC drop, but maybe a long trip with rapid charge sessions will bring this back.

EVowner, your case is the worst I have seen, definitely something is not right. Our PCM screen went black only once is 16,000km. And if the car refuses to accept 11kW AC charge, I believe the dealer must do anything to fix that, as it is so obvious and easily reproducible.

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[ChrisFromUK]

Mines been in the 1% club since delivery in April 2025. Just checked and its already 2% down since I parked it 50 hours ago.

The big software update in November didn't make any difference to this behaviour.

However, the update did seem to introduce a different layer of madness with the SoC level which can now change quite significantly (up to 5%) over short periods (couple of hours to a couple of days), more often than not downwards but upwards also. This is quite possibly the battery pack cells being unbalanced but I have run down to 2% and charged up to 95% a couple of times which has only helped slightly. It was also reporting zero miles range at 10% SoC last time I ran down to 2%.

I'm going to have a chat to the dealer about this again next week as I need to book it in to get a dashboard vibration/rattle fixed.

 

[platypus]

What’s “reassuring” in a way is that we’re all experiencing the same symptoms, so it should really be on Porsche’s radar at this point.

 

[EVowner]

Just to be clear as I stated before all the issues are completely random. There are days when car is not dropping SoC and then there are days when it starts dropping SoC and continues to do so at various rates across multiple days. Same with that AC charging. It works fine most of the times, but then multiple charge cycles it just start charging at half of the speed until I stop the charging if I am near the car, replug it and then it works fine for rest of the cycle. I don't believe that it is caused my charger as it worked just fine every single time with loaner Macan.

As I said before I believe certain conditions are triggering this behaviour, but I have not yet figured out what are those. On one hand with all the stuff that my particular PCM is doing I would say that car sometimes just refuses to go to sleep properly and it is computer or some HV module draining the battery which would be in line with other people saying that they think this started happening for them after SW update.

Issue with that SW theory for me is that mine did first SW update in September. My car was produced in June 2025 so at this point it was 2 months old and with around 3K kms. At that time I was already complaining about planner saying that I will arrive with higher SoC than at the start of the journey, car being unable to hit charge limit (always higher or lower SoC then limit), music stopping randomly, blind spot monitor seeing ghosts and rain sensor not working at all (at least this one thing was fixed on first try, with service center stating that it was not seated properly from factory). Whether it was draining already at this point I honestly cant tell as I was using preconditioning often. Service center said that they already saw issue in diagnostic with HV system before doing the update and even at that first visit they were doing something with battery/BMS module (I guess first recalibration of battery as unexpectedly they called me that they need to keep the car overnight and actually returned it to me just before closing next day with them stating that they were working on it till last minute). So this would mean that on my car at least something was wrong with HV system even before any SW update. Also if it would be SW caused why is it affecting only some cars? Maybe some specific combination of equipment in the car and mine came with some faulty SW build from factory?

On the other hand fact that service center saw poor SoH and recalibrated my battery, if what they are saying is true, already so many times tells me that they are getting either constantly strange readings from it or they really don't have any idea and are just trying it over and over again as it is the only thing that they can do (I heard from various sources that service centers see between 30-40% of data in diagnostic and everything else is visible only to Porsche, which sound absurd, but from my experience I tend to really believe it at this point). Like somebody pointed out losses are real as battery is happy to accept charge again, so maybe issue is really in the battery itself? I know Porsche is starting to produce their own batteries with Cayenne EV and I saw them stressing out that they will now thanks to that have much better QA which would maybe point to them knowing that their battery supplier is not very good. That would be in line with many Taycans getting quietly battery swaps these days (luckily their owners can at least see state of their batteries themselves thanks to the tCAN SW). This would technically also explain why, so far they are pretending, as seen on this forum from experiences of others with their service centers, that the issue with discharge on Macan does not exist as replacing batteries on almost brand new cars would be quite expensive problem for them. But I don't want to speculate.

All I know that every day I see more and more owners (not only here in various different threads, but also on various FB Macan owner groups) seeing same issues that I have been seeing for months which on one hand is reassuring me that I am not crazy, but on the other hand I don't think there is a known real fix or even not publicly disclosed known issue to dealers by Porsche, as my dealer is already at the point of discussing potential replacement with me. Scary thing is that there seems to be zero guarantee that new car wont start doing the same thing one day...

 

[MacanEVOwner]

What’s “reassuring” in a way is that we’re all experiencing the same symptoms, so it should really be on Porsche’s radar at this point.

Just curious, but who is “we’re all experiencing the same symptoms”?

It should be noted that after a re-charging session…to 80% or more, it;s NOT uncommon that for the next day, or two one will experience charge re-distribution on the battery…This is normal, and with the re-distribution, one can see a few % drop in the SoC as seen on the driver’s screen. As explained by Google AI:

Key Aspects of EV Charge Redistribution & SoC Changes

• Voltage Relaxation (Battery "Resting"): After you stop driving or finish charging, the battery is in a non-equilibrium state. Lithium ions are not evenly distributed within the cells, and the voltage is temporarily high (after charging) or low (after driving). Over several hours, the battery relaxes to a true equilibrium state, which can make the SoC percentage tick up or down slightly.
• "Vampire Drain" or Passive Drain: While the chemical redistribution is happening, the car's Battery Management System (BMS) is still active. It uses electricity to maintain the battery, stay connected to the app, or run security features, which causes a steady, small, and real decline in SoC over time.
• Temperature Effects: Cold temperatures cause the battery to become less efficient. The BMS may activate heaters to protect the pack while parked, consuming power and reducing the reported SoC.
• Typical Behavior: Many modern EVs experience a small, normal loss of 0.5%–3% of charge per day when parked, commonly known as "vampire drain".
  ScienceDirect.com +4

Why This Matters

• Inaccurate Estimates: When you park after a long drive and see 30%, you might return a few hours later to see 28% or even 32% as the battery equilibrates.

 

[platypus]

Fair question. Here's the pattern that keeps showing up across multiple owners (I asked Claude to help):

• Sustained 1%/day drain over weeks, not a one-time adjustment after charging
• For many of us, it started after a specific SW update (byebye: fine for months, then 1%/day after Oct 2025. Dekord: zero issues for 6 months, then 1%/day after May 2025 update. Mine started after a June 2025 dealer visit)
• Dekord noticed that when drain is happening, battery temp is 3-4°C above ambient, suggesting the BMS is actively doing something. And below 30% SoC, the drain stops entirely and temp drops to ambient. That doesn’t look like voltage relaxation.
• Multiple owners (M324, EVowner) confirmed their loaner Macans had zero drain under identical conditions. Same charger, same garage.
• BMS resets haven't fixed it (craz8 confirmed).

In my case, the car is plugged in. It charges back from 78 to 80% every couple of days. That's real energy being pulled from the grid, roughly 1 kWh/day disappearing somewhere.

EVowner's case is clearly more severe (12% in 10 hours, 91% SoH after 6 months), which looks like a hardware problem on top of whatever BMS bug the rest of us have.

My current guess: a SW update broke something in the BMS sleep cycle. It keeps doing balancing or thermal work instead of going to deep sleep, which would explain the suspicious timing, the elevated battery temperatures, the threshold at 30%, and why loaner cars (possibly on different SW versions) don't have the issue.

 

[MacanEVOwner]

Fair question. Here's the pattern that keeps showing up across multiple owners (I asked Claude to help):

• Sustained 1%/day drain over weeks, not a one-time adjustment after charging
• For many of us, it started after a specific SW update (byebye: fine for months, then 1%/day after Oct 2025. Dekord: zero issues for 6 months, then 1%/day after May 2025 update. Mine started after a June 2025 dealer visit)
• Dekord noticed that when drain is happening, battery temp is 3-4°C above ambient, suggesting the BMS is actively doing something. And below 30% SoC, the drain stops entirely and temp drops to ambient. That doesn’t look like voltage relaxation.
• Multiple owners (M324, EVowner) confirmed their loaner Macans had zero drain under identical conditions. Same charger, same garage.
• BMS resets haven't fixed it (craz8 confirmed).

In my case, the car is plugged in. It charges back from 78 to 80% every couple of days. That's real energy being pulled from the grid, roughly 1 kWh/day disappearing somewhere.

EVowner's case is clearly more severe (12% in 10 hours, 91% SoH after 6 months), which looks like a hardware problem on top of whatever BMS bug the rest of us have.

My current guess: a SW update broke something in the BMS sleep cycle. It keeps doing balancing or thermal work instead of going to deep sleep, which would explain the suspicious timing, the elevated battery temperatures, the threshold at 30%, and why loaner cars (possibly on different SW versions) don't have the issue.

Good analysis.

 

[craz8]

a SW update broke something in the BMS sleep cycle. It keeps doing balancing or thermal work instead of going to deep sleep

Mine did not start with a software update, but otherwise I agree.

I suspect that low usage - periods of no driving, and/or, lots of short trips - cause something to get confused in tracking SOC which then triggers the BMS to work too much. When I was driving longer trips last year, I did not see this problem

The key thing to measure this is to do it over several days. Due to shutdown usage, ongoing cooling, 30 minutes of powered on accessories, and correct BMS balancing after a drive or charge, a single night's loss or change is entirely expected.

However, the only way to see the change is to go to the car, open it up, and turn it on. The app can't tell you the car battery status over time. Each time you turn the car on, it will restart some of those shutdown activities, so you can't measure daily with the car displays.

I think this failure escalates to needing a BMS reset, and might also cause excess battery work that ends up with the bad cases some here have hit.

I have reported this to my service guy as a note that will likely turn into something. Those of us with the issue need to report this to our dealers to give Porsche a chance to see these reports. If anyone knows how to report a technical issue to Porsche USA directly that would help too.

The Audi PPE cars might be having similar problems, but I have no idea where those folks hang out - having a known problem in that group would help get Porsche focussed on a fix for us.

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