Battery cells reset/rebalancing after erratic SoC readings

[Fly4ever]

There are so many threads I could use to post my experience, however I thought it would be a way better idea to introduce a new thread regarding the SoC readings and the associated battery actual SoC (not the same thing,unfortunately,as I recently realized!)Besides,this thread will most likely provide answers and explanations to so many of us and it would be applied to so many threads in regards to the same or related issues.

As I was completely fed up with what my SoC % was keep telling me about my range and battery which were completely out of place according to what I was getting from a charger and what the car system reported I actually got,I started to suspect the SoC % was completely false for unknown reason(s).It wasn't like this right from the start but rather gradually,charge after charge and use after use the remaining power inside my battery as reported by the % SoC became more and more unrelated to the actual remaining power inside the battery.I then started to monitor how many kWh a charger was delivering for a certain charging session and how much the car "thought" it was getting: For 50% according to the SoC % there were only just 31kWh of energy delivered by the charger.Wait...50% should normally be equal to 47,5kWh,not 31!!Where were the other 16,5kWh???Was still in the battery but somehow failed to be seen and reported by the SoC system?Additionally,whatever % reported by the SoC system was actually true or there was a chance the 80% was in fact 70 or 60 or even lower??I suspected the readings were all over the place and completely unreliable so I decided to perform the so called battery cells rebalancing or SoC% reset as I called it.

I drained the battery in driving sessions in a couple of days.Every time the reported remaining SoC was going up after a couple of hours the sessions ended:while driving went down to 11%,session ended,car parked.Couple of hours later it went up to 14%. Another driving session and went to 7%,session ended,car parked.A while later went up again to 11%!!Another session around my city block this time (turtle mode and all warnings about the reduced range were on) and car parked at 4%. From then on I decided trying to reduce even more what was remaining in the battery by using only power hungry features inside the car like maximum heating everywhere inside the cabin rather than driving to avoid surprises on the road as the reported remaining Km display was now just "--" (0). Even though it reached at 2% an hour later went up again to 4% so I realized there simply wasn't an easy way to get it so low and left it at that low 4% state for 24 hours.It showed exactly the same the next day when I plugged the car in (22kWh charger) with the charging slider all the way up to 100%. Normally I should get approx.91kWh (remaining 4%=3.8kWh,95-3,8=91,2kWh) in 8 hours 40min given an avg of 10.8kW/hour charging speed.This was the exact time I was getting from the car for the charging session to be completed.I though,o.k. that's a good sign,the car "knows" it must receive another 91kWh to top up up to 100%!!!
However,at some point I started to realize that the charging session will be completed way sooner than calculated (the SoC % was constantly showing considerably higher values from what it should) in fact it ended an hour sooner!!I got exactly 80.28kWh according to the charger.Another confusion as I did the math...!!!There must be another 10-11kWh,somewhere!!!But here is the car,saying SoC 100% range 400kM!!!

When I got back to the car couple of hours later I thought:Are you absolutely certain the car has topped its battery?Was there a chance the SoC % system to not represent the actual battery SoC?It certainly was,it shows completely falls readings in the low %,how we can be sure it doesn't do the same in the high %?!!?
Disconnected the plug and plugged it once more with the reading still show 100% SoC.Guess what...:It started a new session and kept going...!!!I though to my self,naahhh...it will not get more than a couple of dozens W and the session will soon be terminated.It didn't!!!!!It kept charging another 9,8kWh ABOVE what the car was reporting as 100%!!!The new charging session lasted for almost an hour,and in fact was the hour missed from the main session earlier!!Did the math again: 3,8kWh remaining SoC + 80,28kWh main charging session + 9,8kWh secondary session = almost 94kWh.Even there was still 1kWh missing I'm sure if I would plug the car again after a while or so I'll certainly get it but doesn't mind,it won't bother me much.At least not now I know what's going on here!!Car still shows 100% now but the range went up almost another 19% to 475Km!!!

What's going on here?Definitely the SoC % system for some unknown reason(s) gradually "detach" from the actual battery SoC and start to behave erratically showing completely irrelevant readings.As the problem remain undetected therefore unsolved the readings are getting even more inaccurate,lower than the real SoC in the lows and higher in the highest actual battery SoC.Seems the gap between the actual SoC and the indicated % is getting larger below 50% and in favor of lower indicated values and vice versa above 50-60%.As we constantly charge from around 25-30 to 70-80 the issue is getting even worse and in the end no one knows at what SoC we are when we start a charging session and at what SoC we end it.Fact is the reported 80%,90% or 100% are definitely NOT REAL therefore the car never has the amount of energy displayed by the SoC% reading.

I need to underline here that I don't think all cars are having the same issue,I'm sure most of them are behaving perfectly fine.But for some reason(s)yet to be discovered some cars start to behave that way.Maybe a problematic charging session?Who knows...Thing is the issue has at least "this solution" which can be performed by us without the need to visit a service center.Certainly a service center will perform the procedure way more completely, scientifically and professionally and also without the need to have to drive our cars at a such low indicated %SoC/0Km even if we still know there's still more energy in there that the one we see!!But at least we now know the energy is there even if we've been reported otherwise.As well as that it's highly likely that in most cases we get considerably less kWh when a charging session ends than what the car tell us it got.I simply don't know yet if I do the same after a charge ending at 80% for example there will be some more kWh to get in order to reach the actual/real 80% battery as I don't know if the "trick" will also work for lower SoC other than 100%.

I also wouldn't be so surprised if the SoC 1% reduction when the car remain parked has something to do with all of this!Maybe it's only phenomenal rather than real...!After all with such SoC indication system everything seems possible!!

Please excuse my lengthy post,I wanted to analyze as much as possible the procedure and my experience as well,I believe that many fellow owners will find some answers and hopefully a likelihood solution to this issue which appears to affect quite many of us in here!!

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[F2M]

Wow. What a nice summary.

I remember that in another thread somebody mentioned that switching the logged in user to Guest (or maybe any other as well) would lead to a correct SOC % display. It seems to be tied to driver/user/profile.

 

[sor]

https://www.macanevowners.com/forum...-how-cosmic-rays-charged-my-car-or-not.24080/

 

[chaz]

AI Key take‑aways from the post

Area	What was observed / done	Why it matters
SoC % drift	The battery percentage that the car shows gradually becomes unreliable. After many charge‑drain cycles the reported SoC no longer matches the real amount of energy in the pack.	Drives people to over‑ or under‑estimate range and charge levels.
Low‑SoC under‑reporting	50 % SoC appeared to correspond to only ~31 kWh delivered by the charger (≈ 47.5 kWh expected). The 4 % SoC that was “reached” in a test still held ≈ 3.8 kWh in the pack.	The car thinks the battery is much smaller than it actually is, so it may stop charging early or give a too‑conservative range.
High‑SoC over‑reporting	Even when the charger had only put ~80 kWh into the pack, the car still reported 100 % SoC and a 400‑km range.	The pack can actually hold more energy than the meter says, leading to a hidden “extra” capacity.
Post‑charge SoC jumps	After driving to 0–4 % SoC, the percentage would rise a few points after a few hours of parking (e.g., 4 % → 11 %).	Indicates the SoC calculation isn’t purely based on the pack voltage; recovery or idle behavior skews the reading.
“Reset” / cell‑rebalancing test	The owner drained the pack to very low SoC, then used the cabin heater to load it heavily before re‑charging to 100 %.	This exercise (often called a “cell rebalancing” or “SoC‑reset”) realigned the reported SoC with the actual energy delivered.
Extra charging beyond 100 %	After a 100 % SoC reading was reached, the car still continued to charge for almost an hour, adding ~9.8 kWh beyond what the meter said it had.	Demonstrates that the pack still had usable energy even when the meter claimed it was full.
Range mis‑prediction	With the “reset” performed, the car’s range estimate improved (≈ 475 km instead of 400 km for the same SoC).	Shows the benefit of recalibrating the SoC reading for more accurate range forecasts.
Pattern of the error	The gap between real and displayed SoC widens below ~50 % (real > displayed) and above ~50–60 % (displayed > real).	Knowing this pattern helps users interpret SoC readings at different charge levels.
Scope of the problem	Not every car shows this issue; it seems to appear in some vehicles only, possibly after an anomalous charging session or software glitch.	Users should check if their own vehicle behaves similarly before applying the fix.
Suggested fix	Perform a battery‑cell rebalancing / SoC‑reset (drain to low SoC, load heavily, then charge fully) – can be done by the owner or by a service centre.	Helps align the SoC meter with real capacity, giving more reliable range and charge status.
Open questions	Whether the “reset” trick also corrects the low‑SoC side (below 100 %) and what the exact root cause is remain unknown.	Further experimentation or a software update may be needed.

Bottom line:
Some vehicles’ SoC meters can drift away from the true battery state, leading to misleading range estimates and early charge stops. By intentionally draining the pack to low SoC and then fully charging (often called a “rebalancing” or “SoC reset”), users can bring the meter back into line with the real capacity—though the exact effectiveness may vary and professional service may be required for a full recalibration.

 

[craz8]

Recently, Rivian has had a problem with their LFP batteries - not the same as the Macan, but interesting symptoms.

With a battery, the SOC is estimated based on the voltage of the battery. This works for many chemistries, but is hard for LFP as the voltage doesn’t change much as the battery discharges.

For their LFP batteries, Rivian uses something called ‘coulomb counting’ to track the power in and out of the battery. In this case, they missed some of the power and now you can have no power left despite the SOC reading 20%. The temporary fix for this is a discharge/charge cycle as indicated at the top of this thread.

I wonder if the Macan BMS is doing something similar here. Particularly if there is a phantom 1% per day drain that the car might not be tracking correctly?

My car certainly has some SOC issues - enormous range displayed, adding 5% after a DC charge is balanced, and a drain when sitting for days. I’m currently draining to zeroish to do the reset thing, which with my usage may take a month! (I think low daily usage may also confuse the car - bet they didn’t test for that in the extensive test program!)

Wikipedia has a non-AI page about SOC that is interesting, including the SOC drift you can get from coulomb counting - https://en.wikipedia.org/wiki/State_of_charge

An extra note: The Wikipedia page mentions using a Kalman filter to combine the voltage and coulomb counting techniques. From the text, "The strength of this technique is that a Kalman filter adjusts its relative trust of the battery voltage and coulomb counting in real time". It could be that there might be conditions that cause this adjustment to be wrong for the Macan, and the battery SOC reset process provides better data to the model?

 

[M324]

Wow. What a nice summary.

I remember that in another thread somebody mentioned that switching the logged in user to Guest (or maybe any other as well) would lead to a correct SOC % display. It seems to be tied to driver/user/profile.

This is related to another issue where the navigation shows more SoC% at destination than currently.

 

[M324]

There are so many threads I could use to post my experience, however I thought it would be a way better idea to introduce a new thread regarding the SoC readings and the associated battery actual SoC (not the same thing,unfortunately,as I recently realized!)Besides,this thread will most likely provide answers and explanations to so many of us and it would be applied to so many threads in regards to the same or related issues.

As I was completely fed up with what my SoC % was keep telling me about my range and battery which were completely out of place according to what I was getting from a charger and what the car system reported I actually got,I started to suspect the SoC % was completely false for unknown reason(s).It wasn't like this right from the start but rather gradually,charge after charge and use after use the remaining power inside my battery as reported by the % SoC became more and more unrelated to the actual remaining power inside the battery.I then started to monitor how many kWh a charger was delivering for a certain charging session and how much the car "thought" it was getting: For 50% according to the SoC % there were only just 31kWh of energy delivered by the charger.Wait...50% should normally be equal to 47,5kWh,not 31!!Where were the other 16,5kWh???Was still in the battery but somehow failed to be seen and reported by the SoC system?Additionally,whatever % reported by the SoC system was actually true or there was a chance the 80% was in fact 70 or 60 or even lower??I suspected the readings were all over the place and completely unreliable so I decided to perform the so called battery cells rebalancing or SoC% reset as I called it.

I drained the battery in driving sessions in a couple of days.Every time the reported remaining SoC was going up after a couple of hours the sessions ended:while driving went down to 11%,session ended,car parked.Couple of hours later it went up to 14%. Another driving session and went to 7%,session ended,car parked.A while later went up again to 11%!!Another session around my city block this time (turtle mode and all warnings about the reduced range were on) and car parked at 4%. From then on I decided trying to reduce even more what was remaining in the battery by using only power hungry features inside the car like maximum heating everywhere inside the cabin rather than driving to avoid surprises on the road as the reported remaining Km display was now just "--" (0). Even though it reached at 2% an hour later went up again to 4% so I realized there simply wasn't an easy way to get it so low and left it at that low 4% state for 24 hours.It showed exactly the same the next day when I plugged the car in (22kWh charger) with the charging slider all the way up to 100%. Normally I should get approx.91kWh (remaining 4%=3.8kWh,95-3,8=91,2kWh) in 8 hours 40min given an avg of 10.8kW/hour charging speed.This was the exact time I was getting from the car for the charging session to be completed.I though,o.k. that's a good sign,the car "knows" it must receive another 91kWh to top up up to 100%!!!
However,at some point I started to realize that the charging session will be completed way sooner than calculated (the SoC % was constantly showing considerably higher values from what it should) in fact it ended an hour sooner!!I got exactly 80.28kWh according to the charger.Another confusion as I did the math...!!!There must be another 10-11kWh,somewhere!!!But here is the car,saying SoC 100% range 400kM!!!

When I got back to the car couple of hours later I thought:Are you absolutely certain the car has topped its battery?Was there a chance the SoC % system to not represent the actual battery SoC?It certainly was,it shows completely falls readings in the low %,how we can be sure it doesn't do the same in the high %?!!?
Disconnected the plug and plugged it once more with the reading still show 100% SoC.Guess what...:It started a new session and kept going...!!!I though to my self,naahhh...it will not get more than a couple of dozens W and the session will soon be terminated.It didn't!!!!!It kept charging another 9,8kWh ABOVE what the car was reporting as 100%!!!The new charging session lasted for almost an hour,and in fact was the hour missed from the main session earlier!!Did the math again: 3,8kWh remaining SoC + 80,28kWh main charging session + 9,8kWh secondary session = almost 94kWh.Even there was still 1kWh missing I'm sure if I would plug the car again after a while or so I'll certainly get it but doesn't mind,it won't bother me much.At least not now I know what's going on here!!Car still shows 100% now but the range went up almost another 19% to 475Km!!!

What's going on here?Definitely the SoC % system for some unknown reason(s) gradually "detach" from the actual battery SoC and start to behave erratically showing completely irrelevant readings.As the problem remain undetected therefore unsolved the readings are getting even more inaccurate,lower than the real SoC in the lows and higher in the highest actual battery SoC.Seems the gap between the actual SoC and the indicated % is getting larger below 50% and in favor of lower indicated values and vice versa above 50-60%.As we constantly charge from around 25-30 to 70-80 the issue is getting even worse and in the end no one knows at what SoC we are when we start a charging session and at what SoC we end it.Fact is the reported 80%,90% or 100% are definitely NOT REAL therefore the car never has the amount of energy displayed by the SoC% reading.

I need to underline here that I don't think all cars are having the same issue,I'm sure most of them are behaving perfectly fine.But for some reason(s)yet to be discovered some cars start to behave that way.Maybe a problematic charging session?Who knows...Thing is the issue has at least "this solution" which can be performed by us without the need to visit a service center.Certainly a service center will perform the procedure way more completely, scientifically and professionally and also without the need to have to drive our cars at a such low indicated %SoC/0Km even if we still know there's still more energy in there that the one we see!!But at least we now know the energy is there even if we've been reported otherwise.As well as that it's highly likely that in most cases we get considerably less kWh when a charging session ends than what the car tell us it got.I simply don't know yet if I do the same after a charge ending at 80% for example there will be some more kWh to get in order to reach the actual/real 80% battery as I don't know if the "trick" will also work for lower SoC other than 100%.

I also wouldn't be so surprised if the SoC 1% reduction when the car remain parked has something to do with all of this!Maybe it's only phenomenal rather than real...!After all with such SoC indication system everything seems possible!!

Please excuse my lengthy post,I wanted to analyze as much as possible the procedure and my experience as well,I believe that many fellow owners will find some answers and hopefully a likelihood solution to this issue which appears to affect quite many of us in here!!

Very good summary! As I am having the same issues, I guess I'll give it a try. But as I understand you, this hasn't fixed the root cause, right? You "just" figured out what's happening.

BTW: In the outofspec review on YouTube about the new GTS, Kyle mentioned that the new Macans in all countries now come with a new battery delivered by Samsung and no longer with the one from CATL. Maybe that's one of the reasons?

 

[Awaz]

I checked on Google search; it seems a switch to Samsung batteries applies only to vehicles sold in South Korea.
Porsche Switches Macan EV to Samsung SDI in South Korea

 

[Fly4ever]

Very good summary! As I am having the same issues, I guess I'll give it a try. But as I understand you, this hasn't fixed the root cause, right? You "just" figured out what's happening.

I'm glad I'm helping other fellow owners facing similar issues!!
Obviously I don't know why this is happening as my knowledge on how things are working is quite limited.And I'm afraid neither at Porsche themselves know what's going on here.I'm trying to find out if there are any common factors amongst all of us facing the issue.As an example,I also don't use the car so much but rather sporadically and then again for relatively small driving sessions. Sometimes the car stays in the garage for some days in a row.Friends of mine who bought their cars almost simultaneously, both aren't having such problems.
Or maybe a bad charging session (which indeed happened to me almost right after I got the car) triggered something inside BMS or the battery itself.
I'll keep investigating,next will be a series of test/charging sessions to see if the same phenomenon occurs when the charging limit is set lower than 100% full charge.I'm more than curious to see if a charging session limited to 70% ends what will happen when I reconnect the plug agter a while without using the car at all.
We'll soon know more on the subject... keep searching!!

 

[craz8]

I also don't use the car so much but rather sporadically and then again for relatively small driving sessions. Sometimes the car stays in the garage for some days in a row

This is exactly my recent usage over the last 3 months.

I've been keeping my charging limit at 75 or 80%, with the Battery Preservation setting selected. It does rebalance to a higher % once charging is complete, which I hope the reset will fix.

 

[EVowner]

Please dont take this the wrong way. I own this "marvel of german engineering" too and I have also spent way too much time trying to figure out WTF is hapenning with my car.

I had higher SoC reported issue during navigation (It was me who reported guest account fix after dealer was unable to fix it for several months), I had and still have phantom drain, unable to hit charge limit SoC, high consumption and now massive drops of SoC. On top of that I have blind spot monitor seeing ghosts and audio stopping playing randomly during drive.

I am just curious at which point we as the owners should conclude that there is something very wrong with these cars (there are more and more owners reporting same issues) nstead of trying to come up with voodoo like rituals in effort to fix botched design and crappy diagnostics that does not allow by design even dealers to see full sets of data.

I am sorry, but I find it baffling that on almost brand new cars with 100k+ pricetag owners are forced to be doing these kind of mental gymnastics and tests themselves rather than bringing their weirdly behaving cars to service centers and demanding proper fix or refund.

 

[craz8]

For me, I want to have specific information to give to my dealer to show exactly how the problem presents, I've already asked for a battery reset for this problem using this bulletin https://static.nhtsa.gov/odi/tsbs/2025/MC-11015163-0001.pdf, but my dealer didn't want to do it - it costs them time and money, so it's not a high priority.

If I can show that there's a real issue here beyond the implausible range display - in my case, my car could actually be at 85% SOC whilst charging at a level that it thinks is 80% SOC, putting 70kw extra power into the battery causing possible damage - then I can pursue a resolution with that data in hand.

The dealer model doesn't seem to be great with 'there's something wrong here, can't tell what exactly' type of problem. Having others reporting similar problems helps too, and this forum helps with that.

When I do go to the dealer with specific data, and the bulletin in hand, they are pretty good at providing a fix, but are terrible at diagnosing 'strange things' happening.

My car is drivable currently, but you're right about the quality for the money. This will affect my decision on lease buyout or trade when the time comes.

 

[Fly4ever]

The local leadership was the first I was presented the problem to.Their reaction was totally unacceptable up to the point to even doubt what I was saying and try to convince me it was related to the low temps and my driving style (which by the way was super conservative).I decided then they were completely incapable to resolve the issue,they even didn't want to see it was actually existed in the first place.
That's why I decided to proceed with this procedure which I can now confirm it was 100% successful.In my upcoming post in this thread I'll describe my findings after my last road trip to the same destination 188 Km away with all related conditions affecting range and consumption remaining exactly the same.Stay tuned!!!

 

[EVowner]

Sounds awfully lot as my experience with service center...

I have a meeting with them tomorrow about future of this "dream car adventure" as it was towed to them a day later after they handled it back to me after week of service claiming that at least HV system is now hopefully finally fixed just to see again high consumption and SoC plummet 12% in 10 hours while standing in garage. As reported in another thread I also have photos of battery temp going up during SoC drops (nothing massive, but worrisome as it started happening when drops started being bigger) so I am getting to the point where I am actually afraid to keep that thing in garage and charge it during night.

I understand and to a degree admire your determination to figure out thing on your own, but honestly this is getting ridiculous. They are not only making us beta testers, but they seem to not even willing to acknowledge the fact that they have defective product and instead of apologizing they insult our intelligence by claiming that we are all imagining this.

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