Question about the Charging timer...

[masmole]

when setting the charging timer on the PCM or myPorsche app, does the Taycan initiate charging to reach desired percentage based on a certain fixed AC charging rate? I'm guessing it's not a "smart" system that senses how fast the charging rate was historically or recently based on the location of the AC charging source.

I'm asking because I have a 50A EVSE on a 70A breaker, which enables up to the maximum 48A (11kW) charging on the Taycan, which is obviously higher than the included Porsche PMC. So even if I set the timer to reach 90% charge by 7am, I've noticed that it consistently reaches that charge almost 2 hours earlier than what I set on the timer. Is it because the charge timer in the car assumes Porsche owners are using the crappy PMC units that came with US-spec Taycans?

Perhaps I should set the charge timer 1.5 hours later to compensate

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[Jhenson29]

The EVSE advertises its current limit by setting the duty cycle on the 1kHz control pilot signal.

The car knows the max available current.

Then, the car is the one that determines the current while charging. The EVSE does not (and can not) control the current. It just tells the car what is available and it’s expected that the car respects this.

I don’t know on the 2 hours early. Maybe try deleting and recreating the timer. Or do you have a profile with preferred times set?

 

[daveo4EV]

wow - a lot to unpack here - let me try…

a typical EVSE is rated by it's "breaker" size - so I'm not sure if your EVSE is 50 amps or 70 amps - EVSE's in North America are allowed to run at 80% of the breaker size for continuous load

so it breaks down as follows:

50 amp breaker = 50 * 80% = 40 amps of EV charging or 240V * 40 amps = 9.6 kW charge rate
60 amp breaker = 60 * 80% = 48 amps of EV charging or about 11/12 kW
70 amp breaker = 70 * 80% = 56 amps of EV charging or about 13.44 kW

as you can see from the table above - there is really honestly no 50 amp EVSE - the normal rate of charge would be 40, 48, or 56…it wold help if you could share which EVSE you're using.

now a North American EVSE's job is to tell the EV how much power it can provide - this is normally a static value and it reported to the car when you plug it in…

the Porsche software then uses this value to calculate how long it will take to charge to reach the desired % at the desired time…it will then sit and wait to start the charging session until the calculated time…

now Porsche's software has no reliable method to calculate charging time if the AMP's can change during the charging session

if you plug the car in and the EVSE reports 32 amps is "max rate" - Porsche's software will calculate the necessary charging time based on the reported 32 amp rate- if the amp rate increases during the charging session (which can happen with some EVSE''s) the battery will charge faster and be ready "early"

this could be what's happening - some EVSE "under" report their AMP's but once the charging session starts they "ramp" up to their allowed limit - this can happen for a variety of reasons- the same can happen in terms of ramping down - you can start at 40 amps, but during the session dip down to 20 amps if you're on a shared EVSE circuit and other EV's start charging...

Porsche's software assumes/requires a static EVSE charge rate to predict it's charging window…

this behavior is one of the reasons I prefer schedule based charging (start at my assigned time) vs. depatures based charging (start charging based on a static AMP estimate) - Porsche's system is easily mislead and will not always achieve the goal if the AMP charge rate is variable during hte charging session

you'd have to look at the in car kW's on the lower center console and watch them to see what the actual charge rate is during a session - if it ramps up from where it started then that is why you're finishing early.

 

[daveo4EV]

The EVSE advertises its current limit by setting the duty cycle on the 1kHz control pilot signal.

The car knows the max available current.

Then, the car is the one that determines the current while charging. The EVSE does not (and can not) control the current. It just tells the car what is available and it’s expected that the car respects this.

I don’t know on the 2 hours early. Maybe try deleting and recreating the timer. Or do you have a profile with preferred times set?

also what is reported is only AMPS over the 1kHz signal - if voltage increases or descreases during a session more/less power will be delivered

210 volts * 40 amps = 8.4 kW
220 volts * 40 amps = 8.8 kW
230 volts * 40 amps = 9.2 kW
240 volts * 40 amps = 9.6 kW
250 volts * 40 amps = 10 kW

220/240 is "ideal" voltage but 210-250V is common and acceptable for grid AC powers supply - during the night grid power is under less load and has higher voltage - the Porsche software might be thrown off by getting more voltage that it's modeling for calculations…and getting the greater charge rate - allowing the car to finish "early".

honestly I don't consider the car finishing "early" to be a problem

but the only way to know "why" this is happening is to watch a charging session and see if the actual kW's are higher than normal - otherwise it's a bug in the porsche software and might be time zone related, day light savings or some other software fault.

the Porsche software is not as clever as you make it out to be - it's just calculating linear charge rate based on EVSE amps * voltage and it "knows" how quickly the battery will be filled and then calculating a start time…it's actually quite brain dead.

 

[daveo4EV]

I prefer "schedule based charging" vs. "depature time charging" and think we should have the option to use either method at different locations

I've sent a letter to PCNA about this - I expect no response

but schedule based charging to me is better for off-peak rate management and better absorbs variation during the charging session - the car doesn't have to know/care how fast it will be charged - it just needs to start charging at 11:01 pm…and it will be done when it's reached the target %…

it is my preferred method of charging and to date is impossible with the PCM charging software.

 

[masmole]

as you can see from the table above - there is really honestly no 50 amp EVSE - the normal rate of charge would be 40, 48, or 56…it wold help if you could share which EVSE you're using.

Actually there is a 50 amp EVSE. The Autel Maxicharger has 50A (12kW) model that can be set to 50A, 48A, 40A, 32A, 20A, etc based on the breaker it is installed on. It's a great unit btw and I really love the extensive connectivity features. Although I'm fully aware the stock AC charger inside the Taycan can only do 48A/11kW max rate, I had my electrician hardwire this EVSE to a 70A breaker anyway, which satisfies the 125% rule, and I have the Autel EVSE set to 50A max charging via my iPhone app, knowing full well the Taycan will ultimately control the actual rate. We've been through this in another thread already, so let's get back to my original question....

Porsche's software assumes/requires a static EVSE charge rate to predict it's charging window…

this behavior is one of the reasons I prefer schedule based charging (start at my assigned time) vs. depatures based charging (start charging based on a static AMP estimate) - Porsche's system is easily mislead and will not always achieve the goal if the AMP charge rate is variable during hte charging session

you'd have to look at the in car kW's on the lower center console and watch them to see what the actual charge rate is during a session - if it ramps up from where it started then that is why you're finishing early.

...which you've answered right there in that once sentence. So thank you! That's all I needed to know. I guess I will have change my departure time to 1.5 hours later to compensate for this then.

 

[Jhenson29]

which you've answered right there in that once sentence. So thank you! That's all I needed to know.

You understand that @daveo4EV meant “static” as “it doesn’t change during the charging session”, and not “static” as “set to a fixed value (e.g. 40 amps) in all cars”, right?

 

[daveo4EV]

You understand that @daveo4EV meant “static” as “it doesn’t change during the charging session”, and not “static” as “set to a fixed value (e.g. 40 amps) in all cars”, right?

@Jhenson29 ,as normal, is annoyingly correct…

my apologies for being unclear in my original post.

the "static" value I'm talking about here is what ever value the Taycan "receives" from the EVSE when it's intially plugged in - but it will calculate different charging times for a 16 amp EVSE vs. a 40 amp EVSE - but it will not account for "changes" in the value during the charging session - and it will not "remember" that the last time it used this specific EVSE this is what my charge rate it…

it calculates charging start time based on what ever "non-changing" value the EVSE reports at plug-insertion and initial handshake time - after that it just takes what ever level of charge it can get once the electrons start flowing later…

 

[masmole]

You understand that @daveo4EV meant “static” as “it doesn’t change during the charging session”, and not “static” as “set to a fixed value (e.g. 40 amps) in all cars”, right?

Yes, I get that. So the only workaround for now seems to be changing the departure time to compensate. Worst case, if the departure time is set too late and overcompensates for the discrepancy, I'd just be short a few % of my desired charge level by the time I leave. No big deal in my case. Didn't mean to start a whole exhaustive discussion about it or my motives for wanting to be at that charge level exactly when I leave. But thank you, all. This forum is great.

 

[daveo4EV]

Actually there is a 50 amp EVSE. The Autel Maxicharger has 50A (12kW) model that can be set to 50A, 48A, 40A, 32A, 20A, etc based on the breaker it is installed on. It's a great unit btw and I really love the extensive connectivity features. Although I'm fully aware the stock AC charger inside the Taycan can only do 48A/11kW max rate, I had my electrician hardwire this EVSE to a 70A breaker anyway, which satisfies the 125% rule, and I have the Autel EVSE set to 50A max charging via my iPhone app, knowing full well the Taycan will ultimately control the actual rate. We've been through this in another thread already, so let's get back to my original question....



...which you've answered right there in that once sentence. So thank you! That's all I needed to know. I guess I will have change my departure time to 1.5 hours later to compensate for this then.

thanks this is great information about the Autel - and I appreciate the correction

the Autel is on my short list of recommended EVSE's - and and know it's a great choice.

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