Preheat/Precool function, what is it doing?

[whitex]

I was hoping to see both the battery temp and the g force but I have noticed when engaging the launch control feature, that ring of information changes to a message. I'm wondering, can that information be duplicated on another screen, other than the passenger screen? I'll play around with it and see.

Have you tried just hitting the back button on the steering wheel (with the tube of interest selected)?

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[hifi239]

Batteries warm naturally due to the chemical reaction when used (your mobile will get warm when used a lot) and so if you have preconditioning enabled to heat the cabin (max duration is 1 hour per timer cycle) then naturally this will create heat in the HV battery as that reaction takes place.

The temperature increase is low and will have little or no impact on the car's performance. J1.2 Taycans / Macan EVs appear to run at lower battery temperatures in normal use - I did a 126 mile journey yesterday (ambient 5.5C) in a 4S Macan EV and the battery was at 10C and reached 14C by journey's end. Took it to Ionity for a volt and bolt and the battery reached 32C and maxed at 235kW charge rate.

Actual HV battery pre-conditioning takes this to the next level and aims to raise the battery temp to at least 32C (89.6F) in readiness for optimised charging at a DC charging location (must be >= 50kW). In so doing it also uses available battery capacity (obviously).

The difficulty with this theory is that preconditioning on shore power and a timer doesn’t use the HV battery.

 

[W1NGE]

The difficulty with this theory is that preconditioning on shore power and a timer doesn’t use the HV battery.

First off, not a theory.

It is somewhat obvious that if you have an active departure timer for a target charge and within that you have preconditioning set then the final part of the heating of the cabin will coincide with the departure time (including target charge) whilst still charging.

Set a separate timer with no charging set, connected to your EVSE and I'm 99% certain that shore power won't be used - HV will step up (unfortunately).

I have tried on 2 Taycans now to get preconditioning to use solely shore power but to no avail. I may be mis-programming but I have an end to end Porsche Home charging ecosystem where you'd reasonably expect this to work and draw power from the grid rather than the HV.

In any event it is largely a moot point - preconditioning in this context barely moves the needle on HV warming primarily because its not designed to do so.

 

[hifi239]

I agree that the battery won’t warm from 30F to 62F from the internal resistance of level 2 charging, nor will it warm like that due to internal resistance of running the PTC to precondition the cabin. It won’t warm like that with normal driving which is much more power than the PTC. What I don’t know is whether preconditioning a cold car via the PTC warms the battery coolant intentionally (a valve is opened) or as a side effect (no way to avoid if warming the cabin). But I have gone out after a timer on very cold mornings to a warm cabin to see the battery at 62F. And I thought we concluded that the only time preconditioning happens from shore power only is with a timer.

 

[DES_MX]

Just yo-yo it as others have said, works on every EV. Sport mode, hard accelerate-decelerate to max regen, do it like 10-20 times just before HPC charger arrival (when 3-5km out), then arrive in hot and go max regen plus breaks into the stall?. Not same as full precondition but will raise battery temp nicely “.
Just don’t put sport plus if you have chrono, as it has more aggressive battery cooling from what I understand

 

[whitex]

I have tried on 2 Taycans now to get preconditioning to use solely shore power but to no avail. I may be mis-programming but I have an end to end Porsche Home charging ecosystem where you'd reasonably expect this to work and draw power from the grid rather than the HV.

I realize your software localizations may be different (different country) and I don't have the Porsche management system (not sold here at all), but the only way I can get my Taycan to precondition from shore power is to have the car already charged to the profile minimum, then set a timer with the same target SoC as my profile minimum, and of course the desired cabin temperature. Manual start preconditioning from the app uses the battery, until the battery SoC falls 1% under the profile minimum, then the car starts charging the battery while heating (I have a 19.2kW charger and matching EVSE, which can sustain max heat and still have sufficient balance leftover for battery charging).

As a side note, I forgot to mention, when doing longer trips, I set a preconditioning timer with 100% SoC. This way the car charges from the general profile 85% to 100% just before the trip. This also helps pre-heat the battery a little - there is approximately 2kW efficiency waste when charging, so like a really powerful hair dryer going for an hour or so.

 

[bn8959]

When using a timer the BMS will delay a large proportion of the charging process so it finishes just-in-time for departure. The charging process obviously heats the battery, so this delay is there to ensure you have warmth in your battery for when you leave.
I don’t know if it uses the heater or heat pump to also actively add heat to the battery.

In this example I plugged in the night before and it added about 30% SoC immediately, then paused overnight and added a chunk of charge to meet my 100% target for 15:30. You can see if finished charging a bit before (see the tail-off as it approaches 100%), then a short blast of shore power to preheat the cabin.

 

[hifi239]

I agree that the battery won’t warm from 30F to 62F from the internal resistance of level 2 charging, nor will it warm like that due to internal resistance of running the PTC to precondition the cabin. It won’t warm like that with normal driving which is much more power than the PTC. What I don’t know is whether preconditioning a cold car via the PTC warms the battery coolant intentionally (a valve is opened) or as a side effect (no way to avoid if warming the cabin). But I have gone out after a timer on very cold mornings to a warm cabin to see the battery at 62F. And I thought we concluded that the only time preconditioning happens from shore power only is with a timer.

So I did a test. I plugged into a slowish Level 2 source (6.3kW, 5.8kW into the battery) at 2:30 PM with the battery at 35F and set a timer for 4:30 PM. At 3:30 the battery had warmed to 55F and it still showed 5.8kW charging rate. At around 4:00 the preconditioning kicked in and at 4:30 the battery was at 71F with the cabin warming also. It doesn't appear that the car used the PTC heater during charging prior to cabin heating because the car remained at 5.8kW for at least the first hour. Does Level 2 heat the battery when cold? One way or anther, it does quite a bit.

 

[whitex]

Does Level 2 heat the battery when cold?

Yes (see AC Charging profile). This graphic is from 2020 Taycan documentations provided to service techs during training.

Also, there is wasted heat during charging, approximately 10% of the incoming energy is wasted as heat, i.e. does not make it into the battery.

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