Pre conditioning car and battery from the app.

[f1eng]

I hadn't driven my car for 4 days and it has been cold here and it was covered in ice.

The battery temperature was 3C and charge 77%

I plugged the car in and set the 1 hour preheat though I was actually leaving after 30 minutes.

My dispenser was delivering 7.2 kW, after 30 minutes the battery had been heated to 14C but the charge level had dropped to 75%.

The Webasto heater is rated at 10kW iirc so it looks like it was running flat out heating mainly the battery using more than the mains was dispensing so using a bit of the main battery as well.

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[snstevens]

So just for clarity, if I set a Charging Preheat, I am preheating not only the cabin of the car, but also the battery. Is that correct?

 

[W1NGE]

So just for clarity, if I set a Charging Preheat, I am preheating not only the cabin of the car, but also the battery. Is that correct?

Preheat of cabin only but due to the chemical reaction the battery will warm also. This is not the same as preheating the battery as this only occurs when a charging location is set in the PCM NAV as your destination or stopover..

 

[chun]

There is no way to manually preheat the battery; as per porsche directly.

The only way to preheat the battery is by putting a charging destination in the PCM maps.

By preheating the cabin, you "heat" the battery by simply drawing power to power the cabin heater.

 

[snstevens]

Preheat of cabin only but due to the chemical reaction the battery will warm also. This is not the same as preheating the battery as this only occurs when a charging location is set in the PCM NAV as your destination or stopover..

Ok. This is what I thought...

 

[Neptune]

Fun fact, if you put a charging station in the sat nav and never go there it will always keep the battery warm. probably not great for range.

 

[SergeyIndy]

Fun fact, if you put a charging station in the sat nav and never go there it will always keep the battery warm. probably not great for range.

Battery preheat kills range fast and I do not know if it preheats it as fast as it can or it is smart enough to do it gradually based on the distance to the charging station. The risk of preheating is that it kills range quick and if you arrive at a station and it is out of service you may be in trouble.

 

[d00d]

To get maximum mileage I could see using the charging station in the sat nav trick when it's cold and you're charging at home, then set out in range mode with the shutters closed to keep as much heat in the battery as possible.

 

[whitex]

I've experimented with this a bit, and on my Taycan the preheat works like this:

1. If I just start preheating from the app, the car starts preheating from the battery even if plugged into an EVSE. Once the battery level drops to 1% below the set target, shore power is enabled and charging happens in parallel with the heating - car draws the full EVSE advertised power (typically 19.2kW in my garage, unless my wife's car is also charging, then 9.6kW)
2. If I set a departure timer, the car starts preheating immediately from shore power. EVSE shows a draw of ~3-4kW - much less than EVSE advertised capacity. Battery level does not drop and charging does not start (assuming the timer target is the same as regular charging, so battery starts at that target percentage already)

All these experiments were done inside my garage, so no below freezing starting temps. I've started to just set timers even if only few minutes ahead so that the car uses shore power for preheat. When temps are really low and I want to preheat the battery for a longer trip, I set a timer to preheat and and up the battery charge target - this way the car preheats and charges from 85% to say 95% (or 100% if going far) just before departure. Charging itself heats the battery too (I figure 3-4kW to the heater, so 15kW+ going into battery, 10% loss means 1.5kW heating of battery and electronics).

 

[snstevens]

I've experimented with this a bit, and on my Taycan the preheat works like this:

1. If I just start preheating from the app, the car starts preheating from the battery even if plugged into an EVSE. Once the battery level drops to 1% below the set target, shore power is enabled and charging happens in parallel with the heating - car draws the full EVSE advertised power (typically 19.2kW in my garage, unless my wife's car is also charging, then 9.6kW)
2. If I set a departure timer, the car starts preheating immediately from shore power. EVSE shows a draw of ~3-4kW - much less than EVSE advertised capacity. Battery level does not drop and charging does not start (assuming the timer target is the same as regular charging, to battery starts at that percentage)

All these experiments were done inside my garage, so no below freezing starting temps. I've started to just set timers even if only few minutes ahead so that the car uses shore power for preheat. When temps are really low and I want to preheat the battery for a longer trip, I set a timer to preheat and and up the battery charge target - this way the car preheats and charges from 85% to say 95% (or 100% if going far) just before departure. Charging itself heats the battery too (I figure 3-4kW to the heater, so 15kW+ going into battery, 10% loss means 1.5kW heating of battery and electronics).

I'm not sure how you measured the EVSE draw, but this is very helpful to me in understanding what's going on and how immediate Pre-Heat differs from Timer. Thanks!

 

[whitex]

I'm not sure how you measured the EVSE draw, but this is very helpful to me in understanding what's going on and how immediate Pre-Heat differs from Timer. Thanks!

I have a number of ways to measure, including connecting my own experimental EVSE, but for this I just used my whole house power monitoring from Sense. $199 on Amazon, connects to your distribution panel and wifi so it can show you real time consumption as well as historical usage of my home power usage. It's impossible to miss a 19kW kicking on at home, even 3-4 KW, especially that Sense is actually able to identify what device kicks in, so you can subtract known devices (it "learns" over time, it's hit or miss, for example it's never been able to identify the load sharing EVSE's, but it did in the past identify a 40A plug-in one charging a Tesla).

I was actually rather surprised that timer and manual pre-heat work differently. I expected manual pre-heat to just use shore power from the start. IMO it makes no sense to power the car heater from the battery if plugged in. Unless Porsche thought discharging the battery would generate extra heat? I seriously doubt it through, in-garage preheating is not even maxing out the 10kW onbaord heater, so they could have used it for battery preheat faster than by drawing 3-4kW from the battery. My best guess is different teams implemented the two preheat features, so they did it differently.

 

[f1eng]

Preheat of cabin only but due to the chemical reaction the battery will warm also. This is not the same as preheating the battery as this only occurs when a charging location is set in the PCM NAV as your destination or stopover..

That is clearly what most people on here think and my experience shows yesterday not to be the case.

That is why I posted it.

I had never seen it published explicitly by Porsche but I remember that during arctic testing they found that the car had both poor performance and bad range when starting with a very cold battery, unsurprisingly, and the engineers "did somethin to fix it" adding battery warming to the pre-heat cycle being the only thing I could think it might be.

Where it differs from the charging pre-heat is that it is not trying to achieve the high temperature ideal for fast charging but merely getting it warm enough to have reasonable performance and range straight away in a cold climate.

What you write about the chemical reaction in the battery warming it is certainly true but, as an engineer, my interest was piqued by the numbers I have seen on my car not being consistent with only that, and the pre-heat being set at 1 hour when the cabin will be warm within 10 minutes.

Several times last winter my battery had been warmed more than just chemical reaction would explain hence my experiment yesterday.

This shows, without any doubt whatsoever ( at least to my engineering mind} that the preheat also warms the battery if it is too cold.

It clearly doesn't happen in summer and I don't know how cold it needs to be for this part of the preheat cycle to be initiated, or what the target temperature is but it is clear it must be happening from the data I posted.

 

[f1eng]

So just for clarity, if I set a Charging Preheat, I am preheating not only the cabin of the car, but also the battery. Is that correct?

There is no way of setting a charge preheat other than the sat nav destination.

If you set a cabin pre-heat it is evident from the above data that the battery is part of the process if it is cold enough.

 

[whitex]

On the pre-heat, the car will always preheat the battery to the optimum driving target temperature (see next post on active heating and passive heating details). The diagram below is from Porsche technical documentation for 2020 Taycan Turbo(S), so they might have tuned the ranges a bit since, but the principle I'm sure remains the same (at least for all J1 cars).

One thing you can glean from this is that putting the car in Sport+ mode will heat the battery up for you. IIRC some youtube reviewers used that trick for DC chargers not on the PCM map.

 

[whitex]

More details on how battery heating works in J1 cars, for those interested

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