How many kWh are used for preconditioning?

[ChuckUK]

I have my car charging overnight with a granny charger, which delivers only 2 kW, with a final charge state of 80%. When I activate climate for 10 min in the morning, make coffee etc. and go out it the car, the battery is still at 80%. If I set a departure time for preconditioning, then the battery is usually at 76%. I have preconditioning when not charging activated, but in this instance the car is plugged in. I was wondering if the preconditioning required more than 2 kW and so the 15 or 30 mins that this runs for depletes the battery even when charging. Is there anything else going on?

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[dalola]

I would imagine the preconditioning (climate only) is happening over a longer period of time vs the 10 minute manual operation, and thus the extra draw. I don't know what else would be different? If only 2kw is available, that wouldn't change. Just my guess...

 

[RobbertPatrison]

The PTC heater is 6kW, so if your charger delivers only 2kW, you are draining 4kW from the battery. Running that for 30 minutes is ~2kWh loss in SoC.

 

[kdonnel]

The % charge of the battery is a best guess.

I believe that when pre conditioning your battery is warmed. At that point no only did it use some of the energy in the battery to pre condition but since the battery is warmer it has the ability to accept more energy than when cold. So the % charge will be lower.

I have seen this happen with my car and the natural change in temperature. I have plugged my car in and let it charge to 90% while it is colder. Then overnight the temp swings 20 or 30 degrees to the warmer side. Now my car is at 89% without driving.

 

[jefftuck]

I have my car charging overnight with a granny charger, which delivers only 2 kW, with a final charge state of 80%. When I activate climate for 10 min in the morning, make coffee etc. and go out it the car, the battery is still at 80%. If I set a departure time for preconditioning, then the battery is usually at 76%. I have preconditioning when not charging activated, but in this instance the car is plugged in. I was wondering if the preconditioning required more than 2 kW and so the 15 or 30 mins that this runs for depletes the battery even when charging. Is there anything else going on?

My car finishes charging overnight. I can see that when it fires up for a departure time, it draws the full 11KW for a few minutes, then settles into a couple KW which I think means the battery is ready and now it’s just heating up the cabin. The battery preconditioning will definitely pull more than your 2KW if you let it.

 

[dalola]

I believe it's been confirmed that there is no battery conditioning (warming) if you charge under 36A, so that can be removed from the equation in the OP's case.

 

[Explorer2]

Here's my graph for last Monday when it was pretty cold. Mid teens F outside, mid 30s F in my garage at 5 am

 

[Mach-Lee]

The PTC heater is 6kW, so if your charger delivers only 2kW, you are draining 4kW from the battery. Running that for 30 minutes is ~2kWh loss in SoC.

Incorrect, heater power is LIMITED by the input power. So if your charger is only 2 kW, only 2 kW of heat will be used to heat the battery. They did that so the HV battery won't drain from preconditioning.

Here's my graph for last Monday when it was pretty cold. Mid teens F outside, mid 30s F in my garage at 5 am

FYI if you're curious, the first couple minutes of 7+ kW is heating the battery, power decreases due to the PTC effect as coolant temps warm. Then because the battery warmed up some, it decided your SoC was actually below the charge target and started to CHARGE the battery some more in addition to heating. That's why it went to full available power halfway through. Charge target was reached again 15 minutes later and power dropped down to low levels to maintain heat before timeout is reached.

@ChuckUK I strongly recommend using a charger that can output 7.2 kW or greater for battery preconditioning. With lower power levels, it may not be able to warm up the battery fully in the available time.

 

[ChuckUK]

Incorrect, heater power is LIMITED by the input power. So if your charger is only 2 kW, only 2 kW of heat will be used to heat the battery. They did that so the HV battery won't drain from preconditioning.



FYI if you're curious, the first couple minutes of 7+ kW is heating the battery, power decreases due to the PTC effect as coolant temps warm. Then because the battery warmed up some, it decided your SoC was actually below the charge target and started to CHARGE the battery some more in addition to heating. That's why it went to full available power halfway through. Charge target was reached again 15 minutes later and power dropped down to low levels to maintain heat before timeout is reached.

@ChuckUK I strongly recommend using a charger that can output 7.2 kW or greater for battery preconditioning. With lower power levels, it may not be able to warm up the battery fully in the available time.

Thanks for that info. It does indeed seem that preconditioning is a waste of time for my usage case. I wonder if a precondition how long it will stay ‘preconditioned’ and continue charging that batteries. With an L1 charger I guess there is no chance of recouping the lost battery percentage. Time to plan the 7 kw charger; the problem is the it’s an awkward and long cable route.

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