Charging to 100%, why not?

[Dr Bob]

Sorry guys, maybe has been discussed previously but close to getting a GTS. Simple question to more experience owners, why not charge to 85% and not to 100% every time? Hear me out, on other cars (or electronic devices per se) like Tesla you dont want charge to 100% every time to preserve the battery, HOWEVER, Tesla allows you to use 100% of the battery capacity. On the Taycan only roughly 90% is available to the driver (dont have the exact numbers), remaining 10% are a buffer locked by Porsche.

That begs the question, even if you charge to 100% you never actually charge the battery capacity technically to 100% but only 90%. So why the caution?

If anyone is wondering why ask this question… live close to an EA charger and would charge the car for free…makes more sense to charge to 100% to have less trips to the charger.

Boy, is there some lack of understanding of charging our batteries on here! The myths from the internet are perpetuated and become the norm. Reading this thread gives the reader the impression that 100% SoC is fine but just dont keep it there that long – but is that seconds, minutes, hours or days? Guys (and Gals), you are really not understanding the issues of LFP (or Li ion) batteries.

I'm reasonably new to this forum (I bought a used Taycan 4 months ago) but have significant experience in Lithium batteries. I haven't read all the data in all previous threads on charging but can input from a external perspective. In my day job, I am technical director of a company involved in recycling Lithium EV batteries. This means recovering the important metals as oxides from battery black mass (ie Lithium, Nickel, Manganese and Cobalt) and then re-forming them into cathode materials. I do understand the chemistries of these batteries. I also have 5 years experience of fitting a 5 kWh bank of LiFePO4s (Winston Thunderskys) to a boat – which we spend a lot of time living on, which required me to build my own simplistic BMS to stop overcharging or sub zero temperature charging- so have first hand experience of what can and does go wrong when you charge up to 100% with LiFePO4s. Finally I have 3.5 years experience of charging a Tesla M3 with many charges overnight up to 100%.

Yes, holding an LFP battery at 100% for extended periods is bad for the battery but this is not the main reason why we should worry about taking our batteries up to 100%. Yes, if you want to store the batteries for 3 months, then discharge to 30% as Porsche tells you, but they are fine at 100% overnight if you are charging for a long run (if the batteries are really at 100%). The bottom line is that you do need to charge to 100% now and again but there's no way I would do it on a DC charger every charge, as per the OP's original question.

I'm now going to bore you with the two technical reasons why not! I'll try and keep it simple.

First up, you have to consider the chemistry of what is happening in the battery and what will go wrong as you get to 100% charge. During charging, the lithium ions on the cathode transfer to the anode and at 100% SoC are at the maximum the anode will hold. If the voltage from the charge source then is still higher than the voltage in the cell, further lithium ions will flow but there is nowhere for them to go and then all sorts of things start to go wrong with possibility of dendrites forming (which can short out cells), temperature increases and internal resistance changes etc. Overcharging from 100% is a bad, bad idea. LFP's are better than Lithium ion chemistries and are far less likely to suffer thermal runaways (ie fires) but they will still suffer irreparable damage if charged to over 100%.

OK, so what do we mean by 100% SoC. We really need to consider cell voltage, not SoC as it is not possible to measure SoC – you derive it from other measurements. LFP cells have a max allowable voltage of 4.2V. (Note: this is for typical LFP's – I have no idea what the voltage profiles are for Taycan cells but that's not important for this explanation) At that voltage, the cell is fully charged and the anode will not accept any more ions. You must not exceed 4.2V in any cell during charge. Now, this will be easy to manage if all your cells are exactly the same voltage during charging but unfortunately that never happens. Slight differences in capacity and internal resistance will mean you get some cells at slightly higher voltage and will enter the 'voltage knee' of the charge/voltage curve sooner than the rest and their voltage then shoots up and they reach the 4.2V (or 100% SoC) ahead of the rest. As soon as one cell reaches 4.2V you must stop charging. This is why when we see 100% SoC on the screen, the car is telling porkies. The real SoC will be lower to ensure no one cell ever goes over 100%. The issue then is how to keep all the cells nearly the same – and this is where balancing comes in. The BMS will control balancing but it doesn't happen immediately ie in seconds, but over a period of 4-24 hours. If a cell bank is well out of balance, then you could have some cells reaching 4.2V while some are still down at 3.6V. One important piece of information that is often ignored is that charging to 4.2V is likely to initiate balancing issues which then gives the BMS a lot of work to do and that could lead to damage. It is far better for the battery health to avoid charging into the voltage knee so reducing out of balance issues. On my boat, I have a 4kWhr LFP bank and in the 5 years I have had them, I have never charged above 85% and never had to re-balance any cells after the initial installation (I have no automated balancing). Taking cells to 100% SoC (whatever that means) risks getting cells over the 4.2V through poor balancing.

Another issue here is that our cells are top balanced, ie the balancing is done as we charge to 100% SoC, but what that means is that if cell capacities vary due to long term charging effects, they will not be balanced at the bottom end of the SoC curve and could be a long way out. Everything may look fine at 95-100% but at the end of discharge when some cells are at 10% SoC, some laggard cells could be at 0% and that can wreck a battery just as badly as overcharging. If you are worried, take you batteries up to 100% then discharge to say 10% (or 5% if you are brave!) and look at the cell voltages. That's where you may see big voltage deltas between the cells. Lot's of charging up to 100% will put pressure on the balancing and hence the need to watch the balance at the bottom of the discharge curve.

The second technical input why very frequent DC charging to 100% SoC is not good idea, is all around what happens during charge. You can define charge rates based on the capacity of your battery bank therefore charging a Taycan's 93kWhr bank at 93kW is a charge of 1C. Charge at 186kW and we have 2C etc. Charging at 3C is a frightening thought to the battery chemist!!!!, but that's what we are doing on these Ionity chargers! The temperature rises and the physical changes in moving ions around quickly cause massive mechanical stress which over time will take its toll on the battery structure. I sat in the car a few nights back on a long trip from Jockland to the Midlands (in the UK) watching the Ionity charger put in 270kW. That is just too fast. On my boat, I charge at C/3, ie 9 times slower than this and still see 10°C temp rises in 30 mins.

One thing I do notice is that the Taycan charges significantly faster than the Tesla ever did – I just wonder if the higher number of battery problems I see on this forum compared to what I saw on the Tesla forums is indicative of our super duper charging speeds. It does make me nervous! Overall though, we need to be able to charge fast – and that is great- and doing it now and again will not cause significant issues – and the Porsche warranty will support that. However, doing fast DC charging every charge cannot be good for the battery structure and likely a lot worse than keeping a bank at 100% SoC for 24 hours.

It is worth mentioning though that we have to take our cells up to over 95% now and again for the system to work. Cell balancing can only be initiated once you are in the voltage knee, so if you get balancing drift at mid SoCs when never going outside 25%- 75% SoC, you could be in trouble when you eventually do go high or low. The other thing is the SoC 'measurement'. SoC is not 'measured' by an instrument. It is calculated by integrating the amps passing in and out of the battery bank. Some clever math is required to do this accurately but this drifts over time (weeks/months) and the BMS needs to re-set the SoC itself which happens once you get well up the voltage knee during charging.

So to summarise, the advice to not always charge to 100% is not because these LFP cells dont like being at 100% but because of the inherent dangers of overcharging cells (caused by balancing issues) and not doing it on fast DC chargers all the time because of stress issues on the battery structure. Of course we all need to charge to 100% (and often on fast DC chargers) – that is what EVs need to do, but we need to understand the issues.


On my Tesla, in the 3 ½ years I had it, I estimate 50% of the charging was done on fast DC chargers with the remainder on 3kW and 7kW AC. Battery health was 90% and in the top decile when I sold it. Charging on the Taycan has been similar but these ''very' fast chargers do worry me.

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[Bognar67]

Nice writing.
Side info: Taycan's Max Cell Voltage is 4,2 too.
AFAIK Taycan's BMS is able to balance from 35%SoC.
Attached my cell structure at 90% SoC. Charged from SoC8% with 2,1kW so more than 24H charge that gave good enough time to balance, according to @Dr Bob.
Unfortunately I forgot to take a picture at 8%SoC. Next time will do to extend this.
By the way at displayed 8%SoC the 'Real' SoC was 13% so 5% buffer at that stage.

 

[Dr Bob]

Nice writing.
Side info: Taycan's Max Cell Voltage is 4,2 too.

Thanks Bognar, interesting information.
It raises two issues though that I do not have the answers to.
Firstly, the 4.2V I referred to in 'typical' LiFePO4 cells is the ultimate voltage that must never be exceeded. Most references say that 3.65V is the 'working maximum' that should be the limit of a charging system. My boat system is a nominal 12V and charging to 3.65V per cell gives 14.6V total which is the maximum charge anyone would ever do and is circa 99% charged. The voltage is rising very fast at this point and would exceed 4.2V within a minute if left on charge. I suspect therefore the Taycan LiFePO4's have some doping of other metals to give a higher working voltage. 4.1V at 90% SoC is too high for 'normal' LFP. Anyone know what exactly is the chemistry of the Taycan battery? My Taycan is similar 4.1V at 90% SoC (as guessed by the display).
Secondly, I have seen others report that balancing can be done 'FROM' 35% SoC. I cannot see how that can be. Between 25% and 80%, the voltage/charge curve is on the plateau so it is not possible to determine SoC from voltage and a 'high' cell at say 50% may be a 'laggard' cell once you get into the voltage knee (above 85%). Picking a cell at 35% (that might be 'high') to drain current from would be wrong as as it could cause more of an in-balance. This is how the cells on my boat work. You have to be above 85% SoC to know it is a cell out of balance. I guess, it is in the wording, and more likely is that the BMS can see when a cell needs attention when it is over 85% SoC and then seeks to drain current from that cell during discharge DOWN to 35% (and back up again). That however is not active balancing and may not always be done right, ie you take the power out and hope the cell is then balanced rather than take the power out and then measure the voltage again to confim it is ok.

I like your approach to slow charging - has to be better for the battery and more accurate balancing.

 

[mikezhang31]

Boy, is there some lack of understanding of charging our batteries on here! The myths from the internet are perpetuated and become the norm. Reading this thread gives the reader the impression that 100% SoC is fine but just dont keep it there that long – but is that seconds, minutes, hours or days? Guys (and Gals), you are really not understanding the issues of LFP (or Li ion) batteries.

I'm reasonably new to this forum (I bought a used Taycan 4 months ago) but have significant experience in Lithium batteries. I haven't read all the data in all previous threads on charging but can input from a external perspective. In my day job, I am technical director of a company involved in recycling Lithium EV batteries. This means recovering the important metals as oxides from battery black mass (ie Lithium, Nickel, Manganese and Cobalt) and then re-forming them into cathode materials. I do understand the chemistries of these batteries. I also have 5 years experience of fitting a 5 kWh bank of LiFePO4s (Winston Thunderskys) to a boat – which we spend a lot of time living on, which required me to build my own simplistic BMS to stop overcharging or sub zero temperature charging- so have first hand experience of what can and does go wrong when you charge up to 100% with LiFePO4s. Finally I have 3.5 years experience of charging a Tesla M3 with many charges overnight up to 100%.

Yes, holding an LFP battery at 100% for extended periods is bad for the battery but this is not the main reason why we should worry about taking our batteries up to 100%. Yes, if you want to store the batteries for 3 months, then discharge to 30% as Porsche tells you, but they are fine at 100% overnight if you are charging for a long run (if the batteries are really at 100%). The bottom line is that you do need to charge to 100% now and again but there's no way I would do it on a DC charger every charge, as per the OP's original question.

I'm now going to bore you with the two technical reasons why not! I'll try and keep it simple.

First up, you have to consider the chemistry of what is happening in the battery and what will go wrong as you get to 100% charge. During charging, the lithium ions on the cathode transfer to the anode and at 100% SoC are at the maximum the anode will hold. If the voltage from the charge source then is still higher than the voltage in the cell, further lithium ions will flow but there is nowhere for them to go and then all sorts of things start to go wrong with possibility of dendrites forming (which can short out cells), temperature increases and internal resistance changes etc. Overcharging from 100% is a bad, bad idea. LFP's are better than Lithium ion chemistries and are far less likely to suffer thermal runaways (ie fires) but they will still suffer irreparable damage if charged to over 100%.

OK, so what do we mean by 100% SoC. We really need to consider cell voltage, not SoC as it is not possible to measure SoC – you derive it from other measurements. LFP cells have a max allowable voltage of 4.2V. (Note: this is for typical LFP's – I have no idea what the voltage profiles are for Taycan cells but that's not important for this explanation) At that voltage, the cell is fully charged and the anode will not accept any more ions. You must not exceed 4.2V in any cell during charge. Now, this will be easy to manage if all your cells are exactly the same voltage during charging but unfortunately that never happens. Slight differences in capacity and internal resistance will mean you get some cells at slightly higher voltage and will enter the 'voltage knee' of the charge/voltage curve sooner than the rest and their voltage then shoots up and they reach the 4.2V (or 100% SoC) ahead of the rest. As soon as one cell reaches 4.2V you must stop charging. This is why when we see 100% SoC on the screen, the car is telling porkies. The real SoC will be lower to ensure no one cell ever goes over 100%. The issue then is how to keep all the cells nearly the same – and this is where balancing comes in. The BMS will control balancing but it doesn't happen immediately ie in seconds, but over a period of 4-24 hours. If a cell bank is well out of balance, then you could have some cells reaching 4.2V while some are still down at 3.6V. One important piece of information that is often ignored is that charging to 4.2V is likely to initiate balancing issues which then gives the BMS a lot of work to do and that could lead to damage. It is far better for the battery health to avoid charging into the voltage knee so reducing out of balance issues. On my boat, I have a 4kWhr LFP bank and in the 5 years I have had them, I have never charged above 85% and never had to re-balance any cells after the initial installation (I have no automated balancing). Taking cells to 100% SoC (whatever that means) risks getting cells over the 4.2V through poor balancing.

Another issue here is that our cells are top balanced, ie the balancing is done as we charge to 100% SoC, but what that means is that if cell capacities vary due to long term charging effects, they will not be balanced at the bottom end of the SoC curve and could be a long way out. Everything may look fine at 95-100% but at the end of discharge when some cells are at 10% SoC, some laggard cells could be at 0% and that can wreck a battery just as badly as overcharging. If you are worried, take you batteries up to 100% then discharge to say 10% (or 5% if you are brave!) and look at the cell voltages. That's where you may see big voltage deltas between the cells. Lot's of charging up to 100% will put pressure on the balancing and hence the need to watch the balance at the bottom of the discharge curve.

The second technical input why very frequent DC charging to 100% SoC is not good idea, is all around what happens during charge. You can define charge rates based on the capacity of your battery bank therefore charging a Taycan's 93kWhr bank at 93kW is a charge of 1C. Charge at 186kW and we have 2C etc. Charging at 3C is a frightening thought to the battery chemist!!!!, but that's what we are doing on these Ionity chargers! The temperature rises and the physical changes in moving ions around quickly cause massive mechanical stress which over time will take its toll on the battery structure. I sat in the car a few nights back on a long trip from Jockland to the Midlands (in the UK) watching the Ionity charger put in 270kW. That is just too fast. On my boat, I charge at C/3, ie 9 times slower than this and still see 10°C temp rises in 30 mins.

One thing I do notice is that the Taycan charges significantly faster than the Tesla ever did – I just wonder if the higher number of battery problems I see on this forum compared to what I saw on the Tesla forums is indicative of our super duper charging speeds. It does make me nervous! Overall though, we need to be able to charge fast – and that is great- and doing it now and again will not cause significant issues – and the Porsche warranty will support that. However, doing fast DC charging every charge cannot be good for the battery structure and likely a lot worse than keeping a bank at 100% SoC for 24 hours.

It is worth mentioning though that we have to take our cells up to over 95% now and again for the system to work. Cell balancing can only be initiated once you are in the voltage knee, so if you get balancing drift at mid SoCs when never going outside 25%- 75% SoC, you could be in trouble when you eventually do go high or low. The other thing is the SoC 'measurement'. SoC is not 'measured' by an instrument. It is calculated by integrating the amps passing in and out of the battery bank. Some clever math is required to do this accurately but this drifts over time (weeks/months) and the BMS needs to re-set the SoC itself which happens once you get well up the voltage knee during charging.

So to summarise, the advice to not always charge to 100% is not because these LFP cells dont like being at 100% but because of the inherent dangers of overcharging cells (caused by balancing issues) and not doing it on fast DC chargers all the time because of stress issues on the battery structure. Of course we all need to charge to 100% (and often on fast DC chargers) – that is what EVs need to do, but we need to understand the issues.


On my Tesla, in the 3 ½ years I had it, I estimate 50% of the charging was done on fast DC chargers with the remainder on 3kW and 7kW AC. Battery health was 90% and in the top decile when I sold it. Charging on the Taycan has been similar but these ''very' fast chargers do worry me.

this is fantastic and i love the very scientific but still simple way of explaining things. I have a new found understanding and confidence in my car now.

 

[Scandinavian]

Thanks Bognar, interesting information.
It raises two issues though that I do not have the answers to.
Firstly, the 4.2V I referred to in 'typical' LiFePO4 cells is the ultimate voltage that must never be exceeded. Most references say that 3.65V is the 'working maximum' that should be the limit of a charging system. My boat system is a nominal 12V and charging to 3.65V per cell gives 14.6V total which is the maximum charge anyone would ever do and is circa 99% charged. The voltage is rising very fast at this point and would exceed 4.2V within a minute if left on charge. I suspect therefore the Taycan LiFePO4's have some doping of other metals to give a higher working voltage. 4.1V at 90% SoC is too high for 'normal' LFP. Anyone know what exactly is the chemistry of the Taycan battery? My Taycan is similar 4.1V at 90% SoC (as guessed by the display).
Secondly, I have seen others report that balancing can be done 'FROM' 35% SoC. I cannot see how that can be. Between 25% and 80%, the voltage/charge curve is on the plateau so it is not possible to determine SoC from voltage and a 'high' cell at say 50% may be a 'laggard' cell once you get into the voltage knee (above 85%). Picking a cell at 35% (that might be 'high') to drain current from would be wrong as as it could cause more of an in-balance. This is how the cells on my boat work. You have to be above 85% SoC to know it is a cell out of balance. I guess, it is in the wording, and more likely is that the BMS can see when a cell needs attention when it is over 85% SoC and then seeks to drain current from that cell during discharge DOWN to 35% (and back up again). That however is not active balancing and may not always be done right, ie you take the power out and hope the cell is then balanced rather than take the power out and then measure the voltage again to confim it is ok.

I like your approach to slow charging - has to be better for the battery and more accurate balancing.

Here are two screenshots from my reading of the battery charge. The first is the battery at 95% charge level if I remember correctly. The second one is around 20 %. So would the cells be overcharged at > 4.2 volts??

Interestingly you can clearly identify the two modules that were replaced in September. If I let the car stand for about 12 hours, the cells will all be equal, both at the top level as well as the bottom level. The 95% charge was done with 3.1 kW supply over quite a number of hours. Looking at the charge curve there seems to have been a lot of issues with supply, perhaps many cars charging or the grid supply was unstable.

 

[Jonathan S.]

Glad to hear that my reluctance to road-trip my Taycan given the woeful condition of CCS1 infrastructure in northern New England will help to prevent degradation of the battery health, and ditto for how my occasional DC charging here almost never gets into even the low triple digits — see, glass half full!

 

[Dr Bob]

Here are two screenshots from my reading of the battery charge. The first is the battery at 95% charge level if I remember correctly. The second one is around 20 %. So would the cells be overcharged at > 4.2 volts??

Interestingly you can clearly identify the two modules that were replaced in September. If I let the car stand for about 12 hours, the cells will all be equal, both at the top level as well as the bottom level. The 95% charge was done with 3.1 kW supply over quite a number of hours. Looking at the charge curve there seems to have been a lot of issues with supply, perhaps many cars charging or the grid supply was unstable.

Thanks Peter, very informative.
The fact that you are over 4.2V says that the Taycan cells are operating at a higher cell voltage than 'normal' LiFePO4s. The upper safe voltage must be higher than 4.2V as I suspected in the post above.

Interesting that your wayward cells are lower in voltage at high SoC and higher at lower SoC - indicating the capacity of those cells is higher(?) than the rest. Weird! The voltages leveling out at the top is expected with the balancing via the BMS but I am surprised it levels out at the bottom unless Porsche have found a way to balance at both ends (.....turning lead into gold springs to mind). I must have a closer look at my cell voltages on charging. I bought an OBD thingy when I got the car but have only done an intial check on battery health. You've got me curious!

 

[simcity]

Have I got this right @Dr Bob are you saying the Taycan battery chemistry is LFP and not NMC?

 

[Scandinavian]

Thanks Peter, very informative.
The fact that you are over 4.2V says that the Taycan cells are operating at a higher cell voltage than 'normal' LiFePO4s. The upper safe voltage must be higher than 4.2V as I suspected in the post above.

Interesting that your wayward cells are lower in voltage at high SoC and higher at lower SoC - indicating the capacity of those cells is higher(?) than the rest. Weird! The voltages leveling out at the top is expected with the balancing via the BMS but I am surprised it levels out at the bottom unless Porsche have found a way to balance at both ends (.....turning lead into gold springs to mind). I must have a closer look at my cell voltages on charging. I bought an OBD thingy when I got the car but have only done an intial check on battery health. You've got me curious!

The wayward cells are nearly brand new. The rest of the pack have done more than 55000 km driving and probably 60% fast DC charging.

I will see next time when the SoC is at a low level to see the effect of letting the car stand for a few hours or so.

I need to do a few AC charging runs when back home. Drain to < 10 % rest for a few hours and then Charge to 100% and rest. Then another cycle so that the BMS can calibrate correctly.

I know @Vim Schrotnock got some advice from a Porsche Battery specialist, but can not find that post just now. I did not save that link unfortunately

 

[andb]

I did a reading this evening at 8% SoC and since my last reading from the summer the SoH dropped from 90% to 87% but the cell voltages look very uneven, in portrait mode looks even worst, haha.
I'll let it sit until morning and put it to charge to 100% and check how things change.

 

[Dr Bob]

Have I got this right @Dr Bob are you saying the Taycan battery chemistry is LFP and not NMC?

Sean,
I honestly havent a clue!
I've read many times they are LFP (this forum and other places) but the 4.2V is far too high. 3.65V is the acknowledged high for charging LFPs. 4.2V is Li/NMC technology territory. The vast majority of EV recycling is aimed at NMC and methods for recovering the nickel, manganese and cobalt separately from the Lithium.

 

[Tcar20]

First of all: congrats!

All modern EVs differentiate between a net and a gross battery capacity.
WIth the perf battery, net is 83,7 KWh on the Taycan.

100% means you charged to 83,7 KWh, not 100% of the gross 93,4 KWh.
(That's similar on other EVs, including the Tesla.)

There are various articles on the chemistry and physics, but a short guidance:

• usually (= "daily") between 20-80% (figure readings in car/ app)
• if you immediately leave for a longer trip, occasionally charging to 100% doesn't do harm
  (as you start to unload the electrons immediately by driving)
• occasionally going below 20% doesn't do much harm (not much below 10% though)
• slower charging is better (heat stress, contact corrosion etc.)

If you follow this, your battery will have 100% after 3 years (as tested by many magazines).

I’ve been charging to 100% for 3.5 years and have had no degradation of miles driven on a full charge…in fact, it’s gone up.

I spoke to my dealer early on and the SA told me not to worry about fully charging.

 

[DougFrisk]

Sean,
I honestly havent a clue!
I've read many times they are LFP (this forum and other places) but the 4.2V is far too high. 3.65V is the acknowledged high for charging LFPs. 4.2V is Li/NMC technology territory. The vast majority of EV recycling is aimed at NMC and methods for recovering the nickel, manganese and cobalt separately from the Lithium.

Taycan is NCM 712 made by LG Chem.

Probably no one cares about this but me, but as an addendum NMC and NCM are both used as descriptors. NCM622 and NMC622 are the same thing, 60% Nickel, 20% Manganese and 20% Cobalt. LG Chem used NCM712 instead of 811 to save money on the cost of nickel and NMC712 sure as heck wouldn't.

 

[simcity]

Sean,
I honestly havent a clue!
I've read many times they are LFP (this forum and other places) but the 4.2V is far too high. 3.65V is the acknowledged high for charging LFPs. 4.2V is Li/NMC technology territory. The vast majority of EV recycling is aimed at NMC and methods for recovering the nickel, manganese and cobalt separately from the Lithium.

Here's what's out there on the pack and the cells. They're definitely NMC pouch cells made by LG at the basis of all within the Taycan and e-tron GT...

https://www.batterydesign.net/2019-porsche-taycan/

https://www.batterydesign.net/lg-e66a/

 

[DJ-UK]

Loving the science and learning lots. Different cars different tech, but Jag used to recommend charging the iPace to 100% on AC so the Battery Management System could work its magic and ensure the best battery life. Seemed reasonable to me (that’s what the management system is for), so I did and didn’t notice any real degradation after 3.5 years of use. Having said that, today I typically charge my Taycan to 85% at home, but don’t worry about the occasional 100% before a long trip. Don’t use DC that often, but do go to 90% on long trips when required.

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