Preconditioning & charging planner

[Yves]

You have the answer in this thread.

Charging speed is 36% less efficient at 0C than 25C. It is 12-15% less efficient at 15C than 25C. Not half.

To be 50% less efficient, the battery would need to be over 35C colder, a difference far, far beyond what preconditioning can achieve. Those are the facts. There is nothing more to be said about your unscientific experience involving multiple EV charging factors beyond preheating. I'm sorry you can't come to terms with that.

As someone mentioned i n this thread colder batteries behave not in a predictable way … why do you not believe that I see 130kw between 15C and 22C in one charging session also observed by others And it will not ramp up during that charging test due to heat generated by the charging as one would expect, this is also observed by other members on this forum …

Why call my test unscientific …
- repeated with charging stations I know can deliver power
- repeated with both none pre conditioned and pre conditioned to warm battery
- with warm battery I always get 270kw at 10-20% SOC

But I get it you have all the wisdom and are the only one scientifically qualified.

It’s colder now so will not be able to do the 15C test, but as soon as my SOC drops below 20% I’ll go to a fast charger and take a picture

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[sor]

I refuse to be forced to use the OEM charging planning, regardless of the car. They’re just not that good or flexible.

I might use one if it’s really good, but luckily I’ve never had trouble hitting max charge rates on any of my EVs in Rocky Mountain winters. So speaking generally with EVs tend to just skip preconditioning unless I had to overnight outdoors and I haven’t done anything to warm up already.

This might be because I’ve always started with a garaged car that is reasonably warm (above freezing), it takes hours and hours to chill a battery, and it really takes a very cold battery to meaningfully affect charging rates (approaching 0C).

 

[CHP]

Congratulations, assuming both seabird and Yves are indeed correct, both of you just identified an unobserved factor. Keep me updated.

 

[sor]

I think part of the crux of the issue is this:

1) people report slow charging in the middle of spring or summer all the time. So why assume an extremely slow charge in winter, and specifically an example when a battery is only mildly cool, not freezing, is solely due to lack of preconditioning? Because the next time preconditioning was used and it happened to do better? So is it just something we do from now on for good luck?

2) it only takes one example of a decent fast DC charge in cold temps without precondition to prove preconditioning effects are minor. One experience alone is enough to rule out that preconditioning is the key to fast charging in cool temps, and then you start looking at all of the reasons why sometimes you don’t get fast speeds in good weather too.

That might mean you have to try not preconditioning more than a few times to rule it out as being the thing that doubled charging rates. You may find a small difference is measurable, that’s clear, but certainly if one gives it a go several times they will find charging speed doesn’t get cut in half just because the battery is cool.

That said I agree charging in general is a complex thing, and it’s hard to make sense of it from simply trying a few different things and drawing conclusions.

Hopefully the battery temp reading is reasonably accurate depiction of the whole battery, as a good starting point. I’ll be doing plenty of cold weather driving and I hope the Macan continues the trend I’ve had the past five years of preconditioning not being necessary to hit max charge speeds.

 

[Yves]

I think part of the crux of the issue is this:

1) people report slow charging in the middle of spring or summer all the time. So why assume an extremely slow charge in winter, and specifically an example when a battery is only mildly cool, not freezing, is solely due to lack of preconditioning? Because the next time preconditioning was used and it happened to do better? So is it just something we do for good luck?

2) it only takes one example of a decent fast DC charge in cold temps without precondition to prove preconditioning effects are minor. One experience alone is enough to rule out that preconditioning is the key to fast charging in cool temps, and then you start looking at all of the reasons why sometimes you don’t get fast speeds in good weather too.

That might mean you have to try not preconditioning more than a few times to rule it out as being the thing that doubled charging rates.

That said I agree charging in general is a complex thing, and it’s hard to make sense of it from simply trying a few different things and drawing conclusions.

Hopefully the battery temp reading is reasonably accurate depiction of the whole battery, as a good starting point. I’ll be doing plenty of cold weather driving and I hope the Macan continues the trend I’ve had the past five years of preconditioning not being necessary to hit max charge speeds.

As mentioned, I have observed this several times: coldish battery … slow charging curve, 25C or warmer fast charging every time …

Now I can imagine that if we see 15C in the display that this is an average … and so it could be that one part is colder like 10C and the car keeps that value to determine how fast it can charge. Unfortunately there is not really a good app for the Porsche battery stats that uses the OBD port. CarScanner is the closest thing, but it’s values are really bizar and you need to do conversions, to make sense of it, which makes me doubt it.

I do not agree that one fast charge at lower temps is proof that it works all the time, otherwise we would not have that discussion and I do agree with the remark of @TomekGnomek that cold batteries do behave erratically … hence I will keep on testing and if the result is better then what I’ve experienced until now, I will also report back, I’m a grown up and can take the flack for it.

I cannot see the battery temp Of the iX without my OBD dongle, but I have a feeling that it is less prone to lower temps, not freezing just lower temps … but that is just gut feeling not scientific in any way

 

[Yves]

OK this is a bummer, in order to get to the bottom of this. I took my OBD reader and carscanner app … and while in the past the values made a bit of sense but needed some interpretation …
After the software update of the car most values stay empty and the ones reported like ODO meter are completely wrong … so the update did completely change the parameters being reported over the CAN bus, they changed the PID’s
It used to “work” as shown here:

 

[Yves]

At the site that can deliver 350 per stall and I was alone at my stall and one other 400v car at another stall, close to the end a Q6 arrived and used the 3ed stall so no shared power and always full power to myself …

What I’ve been telling all along,
from 19% to 49% 12 minutes / 30% charged, battery started at 10C and reached 26 at the end, went further up to 28 after charging stopped, no real increase, as other people have mentioned one stays on the degraded charging curve
I repeat, no pre conditioning you loose 2x the time when you drive the car between 10 and 60%, little less if you charge to 80, but why should you waste time to 80% even the Porsche Nav hardly will go that high for the exact same reason!
12 minutes, the car had been driven 50km that day, 25 just before the charge at 120km/h … so it’s not that it was from a cold standstill either … the battery did ”heat” up during the day by 2C, so from 8 to 10C

My car is perfectly fine and will do 270 kw anytime of the day when pre conditioned …
Make what you will seabird will say that this is either not scientific or that there is a defect with the car or charging station, I can assure you there is none!

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[Yves]

And a picture of the middle part charging

 

[Petzi]

The car shows a total consumption of 2.0 kWh, it's probably stationary

stimmt. es ist eine Fahrt durch eine Stadt. Ich wollte damit nur verdeutlichen, wie viel energie das von einigen hier geforderte Vorwärmen der kühlen batterie direkt nach dem Start kosten würde.

And a picture of the middle part charging

may be. the point is that the heating of the battery would cost so much energy that there would be no gain in charging time. the car calculates this and act accordingly. when you leave with 10c battery temperature and need to charge soon it would 1.) not even be possible for the heatpump to heat the cabin and the battery (at least one hour for 10c) 2.) it would cost so much energy that charging would last even longer. The car tries to reduce charging time as good as possible.

 

[Petzi]

may be. the point is that the heating of the battery would cost so much energy that there would be no gain in charging time. the car calculates this and act accordingly. when you leave with 10c battery temperature and need to charge soon it would 1.) not even be possible for the heatpump to heat the cabin and the battery (at least one hour for 10c) 2.) it would cost so much energy that charging would last even longer. The car tries to reduce charging time as good as possible.

 

[TomekGnomek]

one stays on the degraded charging curve

This is a good observation which I share and which explains a great deal. Once you start charging on the degraded charging curve it will never get back to the optimal one even if the temperature reaches optimal level.

In my case when I start charging with optimal parameters (like 10-20% SoC and warm battery) I instantly get 270kw no problems, it holds it very very well and the total charging time is as advertised by Porsche. BUT if you start in sub-optimal conditions the whole charging curve changes and even when battery reaches optimal temp by 50% SoC I still get 100-150 kw max. You can debate the physics all day but at the end it's the software which controls this process.

The car tries to reduce charging time as good as possible.

And this is also good observation which also explains a lot. I noticed PCM is quite good and planning the route with minimal charging stops and I trust it to do it's job. Only sub-zero temps throws it off balance a bit as the real life charging times can sometimes differ from estimates.

 

[Yves]

may be. the point is that the heating of the battery would cost so much energy that there would be no gain in charging time. the car calculates this and act accordingly. when you leave with 10c battery temperature and need to charge soon it would 1.) not even be possible for the heatpump to heat the cabin and the battery (at least one hour for 10c) 2.) it would cost so much energy that charging would last even longer. The car tries to reduce charging time as good as possible.

Heating the battery costs 2 to 3kwh and I already explained before a roadtrip I will fast charge the car to get a warmer battery the night before departure. 2% is like 1.9kwh it is really nothing …
In 12 minutes I can probably charge from 10 to 60% … or 220km or about 2 hours of highway driving in colder conditions …

I loose 40 seconds charging 3kwh at 270 kw, due to the pre heating so no it’s never ever a good idea to not pre condition the battery if you are driving 1000km+ in the cold. Another benefit is that if you have a quick charging session, your battery goes to 40C and then you are good for the day and pre conditioning will hardly consume any energy …

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