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

[sor]

@sor agreed, in my case the drainage has been 1% consistent every day, and the dealership observed it as well. The rebalancing could also happen on top, because I’ve also recently seen the big changes of SoC.

Yeah a constant daily drainage doesn’t sound like a rebalance, and also sounds abnormal.

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[Petzi]

@sor agreed, in my case the drainage has been 1% consistent every day, and the dealership observed it as well. The rebalancing could also happen on top, because I’ve also recently seen the big changes of SoC.

I would like to come back to the PC's statement. What does "within specifications" mean? Such "specifications" would have to be communicated somewhere. It would be interesting to know whether such a loss is "normal." How does Tesla handle this, for example? I cannot imagine a technical explanation for the "disappearance" of such an amount of energy.

 

[platypus]

@Petzi I think you’re right to push on this, because indeed it would be good to see what Porsche considers normal in their own documentation. I looked at the visit receipt again and it actually doesn’t specify anything (my bad, sorry), so since I’m going to bring it back, I’ll ask them to clarify in writing what is considered normal by Porsche. I don’t have that much hope on this front because I assume they created terms that are favorable to them, even if not normal.

 

[Petzi]

that is what google ai has to say:

The disappearance of charge from a High Voltage (HV) car battery, especially when parked, is
an abnormal symptom that usually indicates an underlying technical issue, such as parasitic electrical loads, a failing 12-volt battery, or an internal HV battery fault.
Unlike a conventional car battery that solely starts the engine, an HV battery powers the electric drive system in a hybrid or electric vehicle and maintains the auxiliary 12V battery.

Common Causes of HV Battery Drain

• Parasitic Loads: The most frequent cause of unexpected battery drain is a parasitic electrical draw. This occurs when electronic components or control modules in the vehicle fail to shut down properly after the car is turned off, continuously drawing power.
  • Common culprits include aftermarket accessories (alarms, dashcams, stereo systems), faulty relays stuck in the "on" position, or issues with computer systems (ECU) not entering sleep mode.
  • Connectivity issues: In some EV and hybrid models, apps tied to a vehicle account (like for remote status checks or smart charging) can constantly "ping" the car, keeping systems awake and causing a drain.
• Failing 12-Volt Battery: All EVs and hybrids still use a smaller 12-volt battery for essential functions, including powering the systems that engage the HV battery contactors to start the car. If the 12V battery is old or faulty and cannot hold a charge, the car's power management system may continuously try to top it up from the HV battery, leading to a noticeable drop in the HV battery's state of charge when parked.
• Internal Battery Issues or Cell Imbalance: The HV battery itself may have a fault. Over time, individual cells within the large HV pack can become unbalanced or degrade, losing their ability to hold a charge effectively. This is common in older vehicles and can lead to rapid self-discharge.
• Software Glitches: In modern vehicles, software issues can sometimes cause the charging logic to malfunction or prevent systems from powering down correctly. Checking for software updates may resolve these issues.
• Prolonged Inactivity/Short Trips: While normal self-discharge is slow, leaving a car unused for extended periods (weeks or months) can lead to significant deep discharge of both the 12V and HV batteries. Conversely, frequent short trips prevent the batteries from fully recharging between uses, gradually depleting their charge over time.
• Extreme Temperatures: Both excessive heat and freezing cold put extra strain on batteries and can accelerate the rate of charge loss.

Recommended Actions

• Consult a Professional: Due to the complexity and high voltage of these systems, you should have the car diagnosed by a certified technician or dealership. They can perform specialized diagnostic scans and safely test components to identify hidden drains or faulty cells.
• Check the 12V Battery: Get the 12-volt auxiliary battery tested. If it's failing, replacing it may resolve the issue.
• Monitor for Parasitic Draw: A mechanic can perform a parasitic drain test using a multimeter to pinpoint which circuit is drawing excessive power when the car is off.
• Drive Regularly: Ensure the car is driven regularly for sufficient lengths of time to allow the battery management system to cycle and recharge the batteries properly.

 

[platypus]

I asked Claude too, and my guess at this point (which is not worth much) is on something like an ECU failing to update and trying indefinitely, as @pm4s suggested earlier, or something else software-related that prevents the car from going to sleep.

 

[Petzi]

I asked Claude too, and my guess at this point (which is not worth much) is on something like an ECU failing to update and trying indefinitely, as @pm4s suggested earlier, or something else software-related that prevents the car from going to sleep.

they have to fix it

 

[platypus]

If you know someone at Porsche that could bump up the priority of this issue, don’t hesitate

 

[Petzi]

If you know someone at Porsche that could bump up the priority of this issue, don’t hesitate

you have a very favorable lemon law in the us. if they do not fix it, a letter from a lawyer will bump up the priority very fast..

 

[platypus]

I’ve been curious about this indeed. I’ll research the best way to bring it up to the dealer.

 

[CHP]

Without dedicated equipment and battery design insights you are unable to measure true battery capacity, state of charge and load. Apple for example only excepts their own health assessment for battery replacement under warranty.

To measure disappearance of charge from a High Voltage (HV) I would first test battery.

Charge your car with 50 kWh and percentage should increase by around 50% (47.5%). Obviously you don't know if a) displayed Macan SoC is correct, b) displayed delivered electricity is correct and c) if Macan received 100% of delivered electricity. Would do a test for AC and DC.

If above adds up, record your SoC, leave your car idle for a few days, record drop of SoC and then charge exactly assumed loss of electricity and record SOC afterwards. SoCs should match. It's an n = 1 observational study. Not science but good enough to make a case.

 

[platypus]

Thanks! I think I’m going to ask the dealer to run and document these tests, I don’t have that kind of time (at least for now)

 

[Petzi]

Thanks! I think I’m going to ask the dealer to run and document these tests, I don’t have that kind of time (at least for now)

as i mentioned earlier: this has to be tested properly: state of health test.
there are independent companies who do this. at least your porsche center should do this and submit the results. of course a positive soh is no guarantee that the draining issue is not existing.

 

[pm4s]

Another simple test would be to get a logging multimeter for example 121GW (225usd on Amazon) & log 12v voltage

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