Preconditioning & charging planner

[seabird]

So just for the sake of moving some of the actual science of EV charging into this thread, I'm starting from the beginning. This will hopefully help explain when the car is or isn't conditioning the battery and why.

For lithium batteries in current EVs, the temperature/behavior looks approximately like this (based on battery pack temperature, not outside air):

• < 0C/32F: battery pack unhappy and inefficient at both charging and discharging. Car will heat the battery to get above this temperature in normal driving because the range lost exceeds the cost of powering the heater.
• 10C/50F: upper limit for conditioning heat usefulness. Above this temperature, range loss of running the heater exceeds any temperature gains other than for fast charging. Most EVs will not heat batteries above this temperature except with a DCFC destination.
• 20C/70F: ideal battery temperature for discharge. No known EV will apply conditioning heat above this temperature, even for DCFC.
• 30C/85F: ideal battery temperature for fast charging.
• 40C/100F: battery too warm. Cooling fans kick in.
• > 50C/120F: battery overheating. Car will aggressively cool down and may limit charging and/or power output until the battery cools down below 50C.

Destination DCFC Preconditioning
Preconditioning can only help if all of the following is true:

1. Battery temperature must be below ~15C
2. State of charge must be above ~10% when cycle starts (or use of power for heating threatens range)
3. Distance to DC charger must be at least ~15 minutes (or heater will not materially change battery pack temperature)
4. Distance to DC charger must be less than ~45 minutes (or battery pack will cool after end of cycle)

This is why it's rare to observe significant temperature gains in mild weather, and also why even in extreme cold, the gains are limited.

Preconditioning Heat Gain Limits
This is where physics rules the roost. The formula is Q=mcT (Heat gain equals mass times specific heat for that material times the change in temperature).

The heating element in most EVs is 5-6kW, and it will run for 20-40 minutes as a cycle. Assuming 100% efficiency (which of course isn't actually happening in reality) and 30 minutes, a preconditioning cycle "costs" 3kWh, or about 10MJ of heat (Q). The mass (m) of the Macan's battery pack and coolant loop/heat exchanger is about 800kg. The specific heat is about 1200 J/kgC. All that works out to roughly 10 degrees C added to the battery temperature by a preheating cycle.

Effect of Temperature on Charging Times
Although the curve is not linear at extremes, the early part of the curve is close. For every 1 degree C temperature drop, charging rates decrease by a little over 1%. So a 10C difference is about a 12-15% slower charge, all things being equal. In other words, if you're getting 240kW at 30C, you're getting about 200kW at 20C initially. But it won't stay 40kW behind for the full charging stop because of the intense heat generated by DC fast charging.

A preconditioned car has an initial advantage, and it can spend longer at the highest part of the charging curve as a result. However, it must also add back the extra energy spent preconditioning, and the higher initial charge rate also means it will hit the temperature ceiling faster and switch to cooling sooner as well, all of which eats into that 15% initial advantage, leveling out at about 10% faster on the 10-80% charge range, or 2-3 minutes on that stop, extending from 21 minutes to 24.

The time lost is front-loaded, so if you shorten your charging stop to end at 50% instead, which in ideal conditions takes 10 minutes, the lack of preconditioning will extend that same 3 minutes to 13 minutes. So in other words, the only way to "double" your charging stop without preconditioning is to stop for under 5 minutes.

How to Read DC Fast Charging Output
The first 30-60 seconds of charging involve a lot of noise. The speeds displayed there are meaningless. Let the charging settle and then look at the speed. You can check in 5 minute increments and compare your SOC, battery temperature, and power delivered to see this in real time.

The only way to measure preconditioning vs. not, if you are desperate to do so and can't just trust the car to manage this, is to look at the difference between the outside air temperature and the battery temperature at the point you (1) start the drive and (2) arrive at the DC charger.

Here is some direct data from a recent 900-mile road trip using EA. The two bold rows at the bottom were preconditioned via PCM stopovers. All others were not, via CarPlay. For reference, a "perfect" 10-80% charge averages 191.7kW. The actual time savings from preconditioning on this trip is 7% (161 vs 150kW) and preconditioning raised the battery temperature 9F (5C and not 10C here, because that was all that was needed to reach 30C/90F).

Ambient	Start SOC	Battery 0min	Batt 5min	Batt 15min	End SOC	Duration	kWh	Avg KW
44F	9%	79F	95F	108F	81%	30min	72.4	144.8
46F	25%	81	108	114	85%	25	60.7	145.5
43	16%	83	112	116	82%	24	65.8	164.5
53	17%	84	114	119	87%	29	70.2	145.2
47	21%	95	122	127	87%	26	67.0	154.8
41	6%	81	92	106	83%	32	74.9	140.4
37	12%	82	107	125	86%	30	76.7	153.4
46	11%	89	121	129	87	30	75.3	150.6
38	5%	92	128	131	87	30	85.6	171.2

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[ron_b]

Not to be dense, but does this need to be in the actual planner, or can you simply select the charging station in the navigation screen and directly drive there?

In sports+ mode I've never noticed any warming, eg if the battery is at 0c, after 10min in sports+ it may be 1c.

I think the statement is more of the charging planner needs to be enabled in order to get the preconditioning. Also, it has to be aware that you would want to charge there. On some YouTube videos, I see people navigate directly to a charging station, this won’t necessarily do any preconditioning because it doesn’t know what the final destination is going to be so it has no idea how much charge you need. You can go into the gear icon and set the minimum charge at destination to a fairly high number say 70% and then you should see it “pick” that charger that you selected as your final destination and it will show a charging duration and if it does that you will get the preconditioning.
I know this is a rather long answer to a short question, the bottom line is if you simply navigate to your actual final destination, and you have your percentages set the way you like them as far as charging stop minimum and final destination minimum then yes all you need to do is set the map. There is no charging planner interaction other than making sure you don’t have it disabled.
Note that people do get this disabled when they don’t like a charging stop and try to remove it, you are prompted with a message saying to do this you will need to disable the charging planner. A better solution is to pick an alternative charging station along the route then the charging planner will generally use that station instead and you don’t need to remove the one you don’t like.

I have had over five years of experience, dealing with the Porsche charging planner on Taycan 4S driving over 100,000 miles.

 

[AlanH]

Very impressive and detailed analysis. Thanks for this. With so much to consider, I think I’ll just let the car do its thing.

 

[ron_b]

Question is - can you set it as a charging stop (which will trigger the calculation of how much time to charge and should trigger preconditioning). Charging stops have a distinct icon on you route planner wich extra options and if you select it as a destination you cannot change charging parameters for this stop.

Though it’s true, you cannot set the charging parameters for the stop if it’s your final destination in the traditional way. What you would do is go to the gear icon and select minimum charge at destination and set it to a high value say 80% then it would make that final stop be a charging stop and it would do the necessary preconditioning, assuming there was enough time to complete it.

 

[ron_b]

I know folks in this forum as well as many YouTube videos have people looking for a manual preconditioning button. Porsche in its wisdom has chosen, not to provide such a button and I believe they are completely correct in this.
To provide a useful manual, preconditioning button would require a dialogue to ask how soon you would be reaching this destination that the preconditioning is needed for and what max charging speed is available when you arrive. Those two facts go into when to start the preconditioning as well as a target temperature. I know some manufacturers offer a manual preconditioning button which arbitrarily choose a temperature to heat the battery and require the user to pick the appropriate time to press the button this can waste needless energy if the button is pressed too soon and then the battery starts cooling down again before you arrive requiring starting preconditioning yet again.
Having the in car Navigation along with the charging planner, select the appropriate start time for preconditioning and target temperature is really the correct solution. The only failure I am aware of is when you intend to use a charger that is not on the navigation system, this is a relatively rare condition. Simply driving aggressively will generally heat the battery to a level that will give a reasonable charging experience. This is from 100k miles in a Taycan.

 

[Yves]

Very impressive and detailed analysis. Thanks for this. With so much to consider, I think I’ll just let the car do its thing.

Yes very detailed but unfortunately not true for many other people including myself. I do finally understand why @seabird claims pre conditioning will have little impact on the travel time …
Lowest battery temp is 79F =26.111 °C = maximum charge power temperature.

He is already at the perfect temp to fast charge so pre conditioning will have ZERO effect that is the whole debate

So let me repeat what many of us really do experience, car outside at below 15C overnight, the lower the temp the lower the battery temp as well and the lower the charging power.

Driving on the highway at 120-140km/h will hardly raise the battery temp. There is no way to pre conditioning the battery other then entering a charging destination or plan your route to the end destination and let the Porsche Nav add charging stations.
It will take a long time to pre condition … so start early with the navigation stuff (people who have sportplus could heat up the battery by going to sportplus, need more info to confirm if this is 100% correct)

When you arrive with that battery at lets say 15C, in my case I get around 130kw, others see similar speed. In one test I had driven 100+km at highway speed in this scenario, battery warmed up to around 16C charging speed 130kw. Also that speed does warm the battery but very slowly, and when it hits ”optimal” temperature it does not go any faster, it stays on the derated charge curve.
It took 11 minutes to add 22kwh.
Same scenario but with pre conditioning
it took 7 minutes to add 29kwh …

I have this experience from September to the end of April as my car is outside and the ambient temperatures at my location and my 80% of the time AC charging make that my battery will be below 15C even after driving 30 or more km’s.

So when going on a road trip during that period of the year, I make sure I fast charge the car the evening before to 70-80% so that battery is nice toasty. I top up with AC charging, it will help to keep the battery temperature up.
And while I would love to use Apple Maps, for roadtrips in these outside temps, I use the Porsche Nav, it saves me at least 30 minutes.

You have diminishing returns if you charge to 80% or over as both charging curves will meet 2/3 into the charging session. But there is a reason why Porsche keeps the car as short as possible on a charge stop as the Nav knows that it is better to keep the car between 10 and 60%, it will hardly go over 60 only if fast chargers are scares …

So to sum it up when your battery is below the ideal fast charging temp use pre conditioning on long trips it will save you at least 30 minutes on long trips … coldish batteries do not like fast charging and pre conditioning is your best friend, plain and simpel and experienced by a lot of other users I know … and yes it takes a long time to get that battery temp up, so start with a warm battery when possible by doing a fast charge the night before and use pre conditioning if your battery temp is below 22C … it will result in 270kw power to around 35% and nice speeds to 60%.
Again this is only when battery and Ambient are low, with higher Ambient the experience can be different and other issues like overheating can come into play, but pre conditioning will help with cooling in this case …


@seabird 79F is warm and toasty for the Porsche Battery and so yeah pre conditioning has zero impact, everybody with that battery temp should know this and experience good fast charging.

 

[Petzi]

@seabird
Thank you very much for this contribution. I believe that this answers all of the questions.

@Yves
the capacity of the heatpump is limited. I think it has 6KWH. That is not much. In cold temps it has to heat the car and the battery. this takes some time. as seabird explained perfectly there is a point where preconditioning does cost more energy than it could save.

 

[seabird]

Yes very detailed but unfortunately not true for many other people including myself.

It is true for everyone, my guy.

He is already at the perfect temp to fast charge so pre conditioning will have ZERO effect that is the whole debate

Again, you misunderstand. You can change the starting and ending temperatures to anything you like. The math will still be the same. You can't add more than 10C by preheating, and 10C can't slow charging by more than 15%.

So let me repeat what many of us really do experience, car outside at below 15C overnight, the lower the temp the lower the battery temp as well and the lower the charging power.

The "perfect temperature" you're claiming IS the car sitting outside at 5C, which is below 15C.

Driving on the highway at 120-140km/h will hardly raise the battery temp.

It does--by at least 5C, as shown in the data.

It will take a long time to pre condition

It will take no more than 30 minutes.

in this scenario, battery warmed up to around 16C charging speed 130kw.

At 16C, the charging speed is reduced from 270kW to to 210kW, not 130.

Your loss of the other 80kW has nothing to do with preconditioning.

Also that speed does warm the battery but very slowly, and when it hits ”optimal” temperature it does not go any faster, it stays on the derated charge curve.

Both false. 130kW generates heat more than 5 times faster than the car's built-in heater AND there is no such thing as "derated charging curve". If the battery is at the optimal temperature, it will follow the optimal curve. It does not matter how the battery temperature got there.

At any given temperature and SOC, there is one and only one maximum charging speed. Real-world performance below that level is down to other factors.

It took 11 minutes to add 22kwh.
Same scenario but with pre conditioning
it took 7 minutes to add 29kwh …

No. Post the temperatures or stop with this nonsense.

 

[Yves]

It is true for everyone, my guy.


Again, you misunderstand. You can change the starting and ending temperatures to anything you like. The math will still be the same. You can't add more than 10C by preheating, and 10C can't slow charging by more than 15%.

The "perfect temperature" you're claiming IS the car sitting outside at 5C, which is below 15C.

It does--by at least 5C, as shown in the data.

It will take no more than 30 minutes.

At 16C, the charging speed is reduced from 270kW to to 210kW, not 130.

Your loss of the other 80kW has nothing to do with preconditioning.

Both false. 130kW generates heat more than 5 times faster than the car's built-in heater AND there is no such thing as "derated charging curve". If the battery is at the optimal temperature, it will follow the optimal curve. It does not matter how the battery temperature got there.

At any given temperature and SOC, there is one and only one maximum charging speed.


No. Post the temperatures or stop with this nonsense.

My Temperatures:
- of the none pre conditioned charge started at 17C and ended at 22C resulting at 1/2 the charging speed or doubling my time at the fast charger 11 minutes for 22kwh
- of the pre conditioned session 25C so it proves exactly my point, got up to even 275kw and added 29kWh in 7 minutes

You just posted a long and winding thread with only posting charging speeds with a battery at optimal temperature and then claiming pre conditioning is not signifcantly reducing charging time, speaking about stating the obvious

 

[AlanH]

Yes very detailed but unfortunately not true for many other people including myself. I do finally understand why @seabird claims pre conditioning will have little impact on the travel time …
Lowest battery temp is 79F =26.111 °C = maximum charge power temperature.

He is already at the perfect temp to fast charge so pre conditioning will have ZERO effect that is the whole debate

So let me repeat what many of us really do experience, car outside at below 15C overnight, the lower the temp the lower the battery temp as well and the lower the charging power.

Driving on the highway at 120-140km/h will hardly raise the battery temp. There is no way to pre conditioning the battery other then entering a charging destination or plan your route to the end destination and let the Porsche Nav add charging stations.
It will take a long time to pre condition … so start early with the navigation stuff (people who have sportplus could heat up the battery by going to sportplus, need more info to confirm if this is 100% correct)

When you arrive with that battery at lets say 15C, in my case I get around 130kw, others see similar speed. In one test I had driven 100+km at highway speed in this scenario, battery warmed up to around 16C charging speed 130kw. Also that speed does warm the battery but very slowly, and when it hits ”optimal” temperature it does not go any faster, it stays on the derated charge curve.
It took 11 minutes to add 22kwh.
Same scenario but with pre conditioning
it took 7 minutes to add 29kwh …

I have this experience from September to the end of April as my car is outside and the ambient temperatures at my location and my 80% of the time AC charging make that my battery will be below 15C even after driving 30 or more km’s.

So when going on a road trip during that period of the year, I make sure I fast charge the car the evening before to 70-80% so that battery is nice toasty. I top up with AC charging, it will help to keep the battery temperature up.
And while I would love to use Apple Maps, for roadtrips in these outside temps, I use the Porsche Nav, it saves me at least 30 minutes.

You have diminishing returns if you charge to 80% or over as both charging curves will meet 2/3 into the charging session. But there is a reason why Porsche keeps the car as short as possible on a charge stop as the Nav knows that it is better to keep the car between 10 and 60%, it will hardly go over 60 only if fast chargers are scares …

So to sum it up when your battery is below the ideal fast charging temp use pre conditioning on long trips it will save you at least 30 minutes on long trips … coldish batteries do not like fast charging and pre conditioning is your best friend, plain and simpel and experienced by a lot of other users I know … and yes it takes a long time to get that battery temp up, so start with a warm battery when possible by doing a fast charge the night before and use pre conditioning if your battery temp is below 22C … it will result in 270kw power to around 35% and nice speeds to 60%.
Again this is only when battery and Ambient are low, with higher Ambient the experience can be different and other issues like overheating can come into play, but pre conditioning will help with cooling in this case …


@seabird 79F is warm and toasty for the Porsche Battery and so yeah pre conditioning has zero impact, everybody with that battery temp should know this and experience good fast charging.

Thanks for all this info and the tips. I’ll be driving to the Alps soon and have not yet experienced cold weather driving and charging. Will my battery warm up enough if I charge it from my home charger (7kw) before leaving? I will definitely use the Porsche nav planner to get that preconditioning. Any other tips for cold weather trips?

 

[seabird]

My Temperatures:
- of the none pre conditioned charge started at 17C and ended at 22C resulting at 1/2 the charging speed or doubling my time at the fast charger 11 minutes for 22kwh
- of the pre conditioned session 25C so it proves exactly my point, got up to even 275kw and added 29kWh in 7 minutes

An 8 degree temperature difference cannot cause a 140kW change in charging speed. I don't know what's stopping you from understanding this. It's not physically possible.

You just posted a long and winding thread with only posting charging speeds with a battery at optimal temperature and then claiming pre conditioning is not signifcantly reducing charging time, speaking about stating the obvious

The fact that the entire post went that far over your head is your own problem.

Nothing changes if you start at 5C instead of 15C. Preheating isn't capable of increasing the temperature more than 10C, regardless of where you start the cycle. In your own example, preconditioning raised your battery temperature 8C, exactly in line with the math.

The only part that seems not to be landing for you is what that 8 degree change is capable of doing for your charging speed.

 

[seabird]

Will my battery warm up enough if I charge it from my home charger (7kw) before leaving?

If you have fully charged the battery when you leave home, the temperature doesn't matter until you're nearing your charging stop.

I will definitely use the Porsche nav planner to get that preconditioning. Any other tips for cold weather trips?

Just use the planner and drive. Let the car condition itself. Don't overthink it and don't try to outsmart it.

 

[Yves]

Thanks for all this info and the tips. I’ll be driving to the Alps soon and have not yet experienced cold weather driving and charging. Will my battery warm up enough if I charge it from my home charger (7kw) before leaving? I will definitely use the Porsche nav planner to get that preconditioning. Any other tips for cold weather trips?

Cool I will drive to the pre Alps to!

- No AC charging will not significantly warm your battery, it will just maintain at best.
- Fast charge the battery the evening before to 70 - 80%, also before you do it pre condition the car going to the fast charger, you want 270kw to heat the battery meaningful … you want to reach 40C or more during this charge as the battery will cool overnight
- charge to 100% on the AC charger so to keep the battery at higher temp of the fast charge.
- Use the Porsche navigation!

 

[Yves]

An 8 degree temperature difference cannot cause a 140kW change in charging speed. I don't know what's stopping you from understanding this. It's not physically possible.


The fact that the entire post went that far over your head is your own problem.

Nothing changes if you start at 5C instead of 15C. Preheating isn't capable of increasing the temperature more than 10C, regardless of where you start the cycle. In your own example, preconditioning raised your battery temperature 8C, exactly in line with the math.

The only part that seems not to be landing for you is what that 8 degree change is capable of doing for your charging speed.

Why do you not do the test yourself instead of citing your experience that as far as I can tell only charges the battery when it is already at optimum …
I posted REAL experiences and you just state they are impossible, shows how far of you went in this conversation, if you do not do the test for yourself and just use armchair reasoning, my advise is do the test for yourself and see what your experience is …


Advising people that AC charging to 100% is enough should be wrong if that car is outside at 5C
… according to your own claims

 

[seabird]

Why do you not do the test yourself instead of citing your experience that as far as I can tell only charges the battery when it is already at optimum …

I can't change the weather. The data is all right there. I don't know what exactly you think would change if the battery started 10 degrees colder. You keep ignoring the fundamental flaw in your claim: 8-10 degrees can't halve your charging speed.

What you can see is that driving does maintain a warmer battery than air temperature. Preconditioning does warm the battery, but at 5C, it's giving an extra 11kW or so. You can double that for a 10C preheat and average 22kW. That's still in the 10% or 3 minute range. In all cases, the battery was ~40C above ambient air temperature by the end of charging. So unless your battery is at -20C to start with (in which case the car is going to heat the battery anyway), that 10% time savings is pretty stable.

I posted REAL experiences and you just state they are impossible,

The charging speeds and times are possible. The reason for the difference that you are claiming is what is impossible.

It is entirely possible to charge at 130kW at a fast charging stop. It is NOT POSSIBLE ANYWHERE IN THE UNIVERSE for a battery that's 8 degrees colder to be the reason for losing 140kW.

if you do not do the test for yourself and just use armchair reasoning

You can't call physics "armchair reasoning" when you don't even understand what is happening. I have done the test myself. So have researchers on thousands of cars completing hundreds of thousands of charging cycles.

Advising people that AC charging to 100% is enough should be wrong if that car is outside at 5C

Good grief. There is nothing to do if you're leaving home with a full charge on a road trip. You won't need to precondition anything for 2+ hours until you're getting ready for a charging stop.

Depleting the battery, doing a DC fast charge the night before, hoping the battery doesn't cool down and all your other nonsense is exactly the kind of terrible overthinking that doesn't help anyone. If the battery temperature is above freezing, don't worry about it.

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