Charging Best Practices

[feye]

Thanks very much. I also figured out that if you log into My Porsche and select the “Charging at Home” service you can see the PMCC connected to your My Porsche account and display the charging history (including the length of charges and total kWh delivered). You can even generate a PDF report by date range.

Thanks, good to know!

I purchased a CPO 2020 TTS from an out of state Porsche dealer. While the PMCC came in the bag in the trunk with all of the manuals and attachments, it doesn’t seem to have the little envelope with the password for the web interface. I really don’t need it given the My Porsche method and others you mentioned but just wondering if there is a way to reset the password?

The little envelope stuck to the charger unit, when it came new.

If you cannot find it, I believe a PC has a master key for them to reset the password - but you need to ask them.

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[kailifish]

Excellent point on the 240V versus 800V - you are correct - I was crossing the input versus output sides! I think all your math adds up - thanks for the correction!

Thanks Squiden and jcroix, very informative posts.

Just curious, I remember seeing Porsche's Battery system allows replacement/repair of individual cells in our battery pack.

So say if we always charge/discharge the pack from 20%~80%, that leaves ~40% of the full battery capacity unused most of the time.

Now does the BMS do,
a) leave the ~40% of cells unused, thus preventing overall battery degradation,

or

b) share the ~60% use/loading onto all of the cells equally, so all batteries degrade at a discounted rate?

If at the end of the 8-year warranty, we can replace individual cells in the pack and thus reduce cost, would strategy a) make more sense compared to b)?

 

[yoursuf]

Dumb question… does it stop consuming power once it reaches to 85%?

 

[daveo4EV]

Dumb question… does it stop consuming power once it reaches to 85%?

yes - the car controls the external “charger“ - actually called an EVSE - the only roll of the EVSE is to respond to “on/off” commands from the vehicle - when the vehicle stops charging it tells the external EVSE to turn off the power flow (like a light switch)

in this design the external charge does not ‘push’ power into the car - the car asks the external charger to let power flow and it accepts the power and charges the battery…the external charger can not force power into the car - it’s an external passive device.

no power is flowing if the car is not charging (for safety) - this is not like laptops or powertools - the power is actually cut off by the car & the EVSE if there is no active charging occurring - *

* -there is a pilot/carrier signal that the EVSE and Vehicle-charger use for communcation - this is like 5V/12V very very low amerage “signal” - it’s purpose is to maintain an electrical circuit so that if the connect is “broken” it can be detected by loss of signal and both ends (the car and the EVSE) will then assure no high power voltage/current is “flowing” - it’s a safety mechanism - the amount of power consumed by this communcations signal is inconsequential and might add up to 0.1 kWh annually or something like that - so the answer is no major power is flowing, but there is some residual power for communication, but as noted is trival

 

[daveo4EV]

Thanks Squiden and jcroix, very informative posts.

Just curious, I remember seeing Porsche's Battery system allows replacement/repair of individual cells in our battery pack.

So say if we always charge/discharge the pack from 20%~80%, that leaves ~40% of the full battery capacity unused most of the time.

Now does the BMS do,
a) leave the ~40% of cells unused, thus preventing overall battery degradation,

or

b) share the ~60% use/loading onto all of the cells equally, so all batteries degrade at a discounted rate?

If at the end of the 8-year warranty, we can replace individual cells in the pack and thus reduce cost, would strategy a) make more sense compared to b)?

how Porsche actually managed the batteries overall capacity (93 kWh) is buried deep in their proprietary battery management software - I doubt anyone outside of Porsche germany can speak authoritatively as to what the actual managment techniques employed by Porsche’s BMS are…we can make well informed speculation, but as to actual management that would require access to confidential internal Porsche design documents and LiON battery models - this type of informatoin varies by vehicle manufacturer and overall capacity goals for the life of the battery - it is likely to vary by manufacture, battery vendor, cell supplier, and could vary even across the the same model generation if there are supply chain differences introduced for battery source material…

the _EXACT_ chemistry of the LiON battery cells varies widely across EV’s and potentially across time due to supply chain changes or simple updates to LiON cells as manufacturing improves or changes - this chemistry and it’s behavior requires subtle changes to how cells are charged and balanced, and I’m sure Porsche is continuously updating their BMS to fit particular battery characteristics that can vary between production runs…

I would find it hard to believe that there are not signficant changes/improvements/variations in the actual batteries of an Oct. 2021 Taycan vs. my July 2020 Taycan- these changes are not consumer visible nor do they represent changes in overall major specifications, but I’m sure the batteries and their cell construction, materials, and exact specifications have varied over time - and I expect some of those changes need to be absorbed by the BMS software and tuned to optimize battery behavior and longevity…

also I expect over time Porsche will update this software‘s behavior as they gather real-world data from the 10’s of thousands of Taycan’s sold that are rolling experiements and data-sets as to actual battery metrics - based on actual observed usage from actual customer batteries fleet wide I would expect Porsche could/would make changes to the battery management policies by updating the battery management software during service visits to either improve warranty claims or battery performance or longevity.

battery management is one of the few bits of “secret sauce” remaining with EV’s where manufacturers can actually compete and it’s hard for their competition to glean insights and parity…

as to if/when the fact that the internal‘s of Porsche’s battery are claimed (by porsche) to be high modular - well that remains to be seen, I doubt Porsche itself will encourage or ever offer fractional battery replacement services at the dealer service level - but enterprising 3rd parties (like ICE tuners today) may find business in servicing out of warranty batteries and replacing modules to extend the life/performance of out of warranty batteries - I have NO DOUBT Porsche factory service will eventually offer refurbished batteries to the market, where they have used the modular factors in their design to simple swap worn out cells for new cells vs. replacing the entire thing. ICE motor’s are highly modular and you can replace only worn out bits while keeping non worn out bits, but most people purchase a “rebuilt motor” where someone else has invested the time/effort to determine which parts needed replacing - batteries will be similar IMHO - most people will buy and entire replacement rather than hunt down and replace the individual parts, but this modularity will be used by the service industry to provide a robust parts infrastructure - some highly motivated individuals will do their own rebuild but most will receive a fully refurbish battery and the old battery will become the next rebuild project for the battery vendor…

GT3 CupCar motors famously have a 40-80 hour service life between rebuilds for optimal performance - and for racing certification the motors are ’logged and sealed’ by Porsche Factory Service regionally - when you need your Cupcar flat-6 motor serviced you send it to Porsche Motorsports and they tear it apart, fix it, measure it’s performance, and send it back to you as a ’sealed’ unit for the next 40-80 hours of service life - I would envision a similar approach to batteries - trained/elite service people can service the battery at a “modular” level - and replace only the cells that need replacing - but this is not practical nor encouraged at the “retail” level - but can be used to maintain a set of replacement parts for the fleet…I’d be surprised if my local Silly-con valley Porsche dealer was ever to ”crack open” a Taycan battery vs. just swapping it with a refurbished part from Porsche (which is what they do most of the time for say a PDK transmission vs. fixing the broken parts inside the tranmission).

 

[biohoodc]

This is my first EV, so beginner question: I have heard it's unsafe (e.g., garage fires) to leave an EV plugged in overnight. Is that truly the case or is that a matter of flukes, poorly installed home chargers, etc. Said differently, is this even a concern if you have a reliable charger, professionally installed and to code?

 

[W1NGE]

This is my first EV, so beginner question: I have heard it's unsafe (e.g., garage fires) to leave an EV plugged in overnight. Is that truly the case or is that a matter of flukes, poorly installed home chargers, etc. Said differently, is this even a concern if you have a reliable charger, professionally installed and to code?

On the basis that your EVSE ("charger") has been professionally installed by a qualified electrician and all to code then there is no reason to worry about overnight charging or leaving your EV connected during the period.

Home charging (overnight) is one of the key advantages to EV ownership particularly when there are more attractive overnight charging rates to be harvested.

I only ever charge overnight at home.

 

[daveo4EV]

leaving it plugged in overnight or days is not risky - no power flows unless it’s charging - sittting there no charging is no different than unplugged - please leave microwaves plugged in for years

 

[kailifish]

how Porsche actually managed the batteries overall capacity (93 kWh) is buried deep in their proprietary battery management software - I doubt anyone outside of Porsche germany can speak authoritatively as to what the actual managment techniques employed by Porsche’s BMS are…we can make well informed speculation, but as to actual management that would require access to confidential internal Porsche design documents and LiON battery models - this type of informatoin varies by vehicle manufacturer and overall capacity goals for the life of the battery - it is likely to vary by manufacture, battery vendor, cell supplier, and could vary even across the the same model generation if there are supply chain differences introduced for battery source material…

oach to batteries - trained/elite service people can service the battery at a “modular” level - and replace only the cells that need replacing - but this is not practical nor encouraged at the “retail” level - but can be used to maintain a set of replacement parts for the fleet…I’d be surprised if my local Silly-con valley Porsche dealer was ever to ”crack open” a Taycan battery vs. just swapping it with a refurbished part from Porsche (which is what they do most of the time for say a PDK transmission vs. fixing the broken parts inside the tranmission).

Thanks @daveo4EV, for the long write up. Very informative

 

[Vim Schrotnock]

OK, first of all, very informative posts. Great stuff. Based on what I'm reading, it's best to simply plug the car in every night for an overnight charge at relatively low current.

Why the heck doesn't Porsche simply recommend this if it is the best way to preserve the battery?? I don't see any recommendations from Porsche for 'optimal' battery charging that states you should simply plug it in every night. Why not?

 

[daveo4EV]

given an 8 year 100,000 mile warranty any charging below 50 kW is not the problem - the most "damage" you could do to a LiON battery is charging it to 100% all the time and letting it "sit" at 100% - or fastcharging at 200++ kW for most/all charging cycles...

keeping your Taycan "ready" at 85% charging at 11 kW or less (standard onboard charger is 11 kW maximum charge rate) is not "the problem" affecting battery life.

use the car, keep it ready, and enjoy.

 

[Fish Fingers]

OK, first of all, very informative posts. Great stuff. Based on what I'm reading, it's best to simply plug the car in every night for an overnight charge at relatively low current.

Why the heck doesn't Porsche simply recommend this if it is the best way to preserve the battery?? I don't see any recommendations from Porsche for 'optimal' battery charging that states you should simply plug it in every night. Why not?

I assume its because not everyone has a home charger.
So these people have no option but rely on public DC fast charging.

 

[W1NGE]

OK, first of all, very informative posts. Great stuff. Based on what I'm reading, it's best to simply plug the car in every night for an overnight charge at relatively low current.

Why the heck doesn't Porsche simply recommend this if it is the best way to preserve the battery?? I don't see any recommendations from Porsche for 'optimal' battery charging that states you should simply plug it in every night. Why not?

Because there is no need to do that

The recomendations come for daily charging limits, long journeys and laying up.

 

[Raphie]

My merc e350e hybrid battery was charged from empty to full like every other day, for 5 years, never 80%, just connect up to 100%, drive empty, connect etc.
After 5Y it measured 81% capacity according to Mercedes Xentry. (They have an 80% threshold warranty) but reality was in summer 29km became 14km, in winter 15km became 5km.
driving electric top speed went from 100km to 70km, before flipping on the ice, because of lack of power. But Mercedes said, this was ‘OK’ en ‘within spec’
they did see it themselves, but did hide behind the software saying 81% (while reality was more like 50%) So pardon me not having to much faith in vendors sorting out <30% range loss under warranty.

 

[whitex]

OK, first of all, very informative posts. Great stuff. Based on what I'm reading, it's best to simply plug the car in every night for an overnight charge at relatively low current.

Why the heck doesn't Porsche simply recommend this if it is the best way to preserve the battery?? I don't see any recommendations from Porsche for 'optimal' battery charging that states you should simply plug it in every night. Why not?

Perhaps because the benefit is not huge, and they don’t want to pigeon-hole their product as only for those who have regular nightly charging available at home. Tesla also stopped pushing this recommendation, even though I know for a fact they use shore power whenever available (for usecases which would use HV battery). To estimate the benefit, say you preconditioned your car twice a day, every single day and always not plugged in. That would be maybe 4KWh per day, so 1460KWh a year of charging and 1460kWh discharging extra per year, or about 15 full charge discharge cycles per year, and that it for a power-user model.

In other words they don't want to have customers obsess over it. Note that even the recommendations of not keeping the car at 100%, limiting DC fast charging, or using the option for battery friendly DC charging ate just recommendations - not following those does not void the warranty. It might get you closer to the warranty threshold in 8 years, or in Tesla cars, might get your max DC charging and/or max range and/or max power reduced over the air while under warranty to reduce chances of failure (no clue if Porsche will do it).

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