Energy Consumption During Preheat

I am borrowing the demo i3 rex from my dealer this Eastern weekend (thanks again, Breeman/Jouke, great job!) And did some experiments.
This night, I fully charged the battery and it achieved 100% after 5 hrs at 2am. This morning, I set the departure time at 9.10 am and at 8.45, the status dropped to 96%. However, the charger LEDs changed from green (stand by) to blue (charging) and the app showed that it should take 15 mins to full charged. And indeed, after 15 mins, the battery, still pre heating, achieved 100% . And at 9.10, the i3 was comfortably heated. I use a charger from EV-box.

Everything works fine so far. It uses energy from the charging during pre-heating.

I just activated the climate control with my iPhone app while the i3 was 100% charged and the charger changed from 'green' to the 'blue' status. The charging status remains at 100% and it's taking it's energy from my home supply. No decrease in battery power.

This morning, I had set the time for pre-heating at 8.45 am. And guess, no consumption from the charger. When I unlocked and locked the doors, the charger turned on.
The dealer said that they are working on an software update to resolve this.

Sorry to clarify but this series of posts says you have been getting inconsistent results with pre-heating?

In your opinion what is the best way to get a warm car at 100% charge on departure?

Bill

Bunter said:

Sorry to clarify but this series of posts says you have been getting inconsistent results with pre-heating?

In your opinion what is the best way to get a warm car at 100% charge on departure?

Bill

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That's true, it's inconsistent. I would recommend to use your remote control to unlock/lock your car 15-20 minutes before you leave. It should not work in this way, but it's in my opinion the only way to be sure that the battery is 100% charged.
If you don't need a 100% charged battery, you obviously don't need to unlock/lock the car.

Lecram said:

That's true, it's inconsistent. I would recommend to use your remote control to unlock/lock your car 15-20 minutes before you leave. It should not work in this way, but it's in my opinion the only way to be sure that the battery is 100% charged.
If you don't need a 100% charged battery, you obviously don't need to unlock/lock the car.

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How does locking and unlocking make the car pre-warm?

Bill

Bunter said:

Lecram said:

That's true, it's inconsistent. I would recommend to use your remote control to unlock/lock your car 15-20 minutes before you leave. It should not work in this way, but it's in my opinion the only way to be sure that the battery is 100% charged.
If you don't need a 100% charged battery, you obviously don't need to unlock/lock the car.

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How does locking and unlocking make the car pre-warm?

Bill

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It does not pre-warm your car, but it will start the charging process when the pre-heater is on. Otherwise, the pre-heater could consume energy from the battery only.

Lecram said:

It does not pre-warm your car, but it will start the charging process when the pre-heater is on. Otherwise, the pre-heater could consume energy from the battery only.

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Arh so if I want to leave at say 11:00, I set the departure time but at say 10:40 unlock then relock the car?

Bill

I noticed if I leave 5-10min later than planned that the car is charged to 100% again. If I leave at the time planned, it will be at 97%.

Bunter said:

Lecram said:

It does not pre-warm your car, but it will start the charging process when the pre-heater is on. Otherwise, the pre-heater could consume energy from the battery only.

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Arh so if I want to leave at say 11:00, I set the departure time but at say 10:40 unlock then relock the car?

Bill

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No, set the dep. time at 11 and unlock/lock the car at 10.40/45. If you set the time at 10.40, your heater will turn off at 10.40 and your car will cool down.

I got the following answer on the question why the battery is not 100 full at departure after preconditioning and why it is not taking power from the charger at all times: (it came from BMW headquarters)

” Required precon. power can be higher than charging power, depending on temperature, SoC and charging supply. Thus SoC can go down even if the vehicle is plugged in! … but will be recharged. some details: at cold temperatures (<0°C), a precon. power of up to 5kW is required. Charging with the standard cable at charging power “low” only delivers ca. 1,4kW, even at “high” only 2,8kW. And: at nearly full SoC, charging power goes down <1kW, no matter if plugged in to a AC 7,4kW charger or even DC charger. This is part of the charging characteristic of every Li-Ion battery.

- SoC can go down up to ca. 10%, if it is very cold/hot and charging power “low”.

- Timing: e.g. at -10°C, preconditioning will start ca. 30min before departure time with 5kW, then go down to 3kW and keep the vehicle warm 15min after departure time. Charging will proceed afterwards (if still plugged in) until the battery is fully replenished.

- All this is independent of automatic preconditioning at departure time or manual activation and charging timer / immediate charging etc.

- Exception: at public charging stations which unlocks after full charge, charging cannot be restarted.

But is this true if you have the 7kw EVSE?

MikeS said:

But is this true if you have the 7kw EVSE?

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Is this bit the answer to your question? (Continental "," Is a decimal "."?)

BMW Technical Centre said:

.....no matter if plugged in to a AC 7.4kW charger...

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To my relatively non-technical mind this seems to be saying that the power for pre-con is taken from the battery, regardless of whether the car is plugged in; then because the charging characteristics mean that the charge drawn by the battery reduces to a pretty low level as full SoC is reached, regardless of current being drawn, the current draw exceeds the charging current. If so it sounds as if the Winter pack, with HV preconditioning will cause even greater depletion during charging, so may not have as much of a beneficial effect on the range as one would have hoped, if any.

I wonder how this reconciles with the way the REx works and perhaps explains why it can't be invoked until down to 80% (or is it 75%). However, I would have expected that the motor would draw direct from the REx, not via the battery, but would draw additional juice from the battery if the load caused the requirement to exceed the max available from the REx. The latter situation would be the point at which the REx isn't able to maintain the charge level, ie uphill at speed.

So if the motor can draw from the REx and only deplete the battery if the motor needs more than the REx can provide, why can't the power users during pre-conditioning draw direct from the EVSE and only deplete the battery if they require more than the EVSE can provide?

Gonville said:

MikeS said:

But is this true if you have the 7kw EVSE?

Click to expand...

Is this bit the answer to your question? (Continental "," Is a decimal "."?)

BMW Technical Centre said:

.....no matter if plugged in to a AC 7.4kW charger...

Click to expand...

Click to expand...

Yes it was! Too early this morning at 0635 for my brain to register the info!

Simon said:

I got the following answer on the question why the battery is not 100 full at departure after preconditioning and why it is not taking power from the charger at all times: (it came from BMW headquarters)

” Required precon. power can be higher than charging power, depending on temperature, SoC and charging supply. Thus SoC can go down even if the vehicle is plugged in! … but will be recharged. some details: at cold temperatures (<0°C), a precon. power of up to 5kW is required. Charging with the standard cable at charging power “low” only delivers ca. 1,4kW, even at “high” only 2,8kW. And: at nearly full SoC, charging power goes down <1kW, no matter if plugged in to a AC 7,4kW charger or even DC charger. This is part of the charging characteristic of every Li-Ion battery.

- SoC can go down up to ca. 10%, if it is very cold/hot and charging power “low”.

- Timing: e.g. at -10°C, preconditioning will start ca. 30min before departure time with 5kW, then go down to 3kW and keep the vehicle warm 15min after departure time. Charging will proceed afterwards (if still plugged in) until the battery is fully replenished.

- All this is independent of automatic preconditioning at departure time or manual activation and charging timer / immediate charging etc.

- Exception: at public charging stations which unlocks after full charge, charging cannot be restarted.

Click to expand...

Thanks for that information, it's very useful and makes complete sense of what I've been noticing and struggling to understand.

If your EVSE cannot supply sufficient power for the pre-conditioning phase the power extra is drawn from the battery.
- When preconditioning my standard UK EVSE draws the maximum 10 amps, the rest is coming from the battery

The consumption during pre-conditioning when cold is likely to be much higher than can be supplied from a standard charging connection.
- That fits, most mornings so far in my ownership the ambient has been below 10 C and the battery is not full when leaving.

If you do draw from the battery, because the SOC is nearly 100 %, charging rate is low, so the energy drawn from the battery takes a long time to replace.

Seems like another good reason to have a 7kw EVSE.

Bill

Bill

First can I add my thanks to Simon.

It looks like I'd read BMW's reply differently from you and re-reading it I think there is some ambiguity. The opening statement 'Required power can be higher than charging power' implies that precon juice is taken from the EVSE and only if the required power is greater than the EVSE power will power be drawn from the battery. So given their example of 5kW at 0C, a 7kW charger would mean that nothing would be drawn from the battery.

But if so, why the comments ' standard cable at charging power “low” only delivers ca. 1,4kW, even at “high” only 2,8kW. And: at nearly full SoC, charging power goes down <1kW, no matter if plugged in to a AC 7,4kW charger or even DC charger'. Surely these would only be relevant if precon juice is taken from the battery, which would immediately start to draw from the EVSE for replenishment but the rate of draw would be limited to the low rates taken when the battery is close to full charge. Then, given the comment that charging power goes down to <1kW, regardless of whether hooked up to a 7kW charger or DC, this seems to be saying that a 7kW EVSE wouldn't confer any advantage over a 3kW EVSE or even a basic 3pin 13A mains lead set-up.

I think the ambiguity is that they keep referring to charging power, which for a 7kW EVSE is always 7kW, when they should be referring to the power drawn by the in car charging controller, which falls as the SoC approaches 100%. Hope the layman's terms make sense.

RJSATLBA said:

So if the motor can draw from the REx and only deplete the battery if the motor needs more than the REx can provide, why can't the power users during pre-conditioning draw direct from the EVSE and only deplete the battery if they require more than the EVSE can provide?

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Because the pre-conditioning power comes only from the battery's DC output, and is not capable of bypassing the charging circuit to use the EVSE's AC output. At high battery states of charge, the charging system protects the battery by limiting current to less than 1 kW, regardless of the power demanded from the battery.

ultraturtle said:

Because the pre-conditioning power comes only from the battery's DC output, and is not capable of bypassing the charging circuit to use the EVSE's AC output. At high battery states of charge, the charging system protects the battery by limiting current to less than 1 kW, regardless of the power demanded from the battery.

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Oh I'm confused again? Mainly because during pre-conditioning the car draws as much as the UK EVSE can deliver (10 amps), even though the car battery is close to 100%.

Bill

Bunter said:

ultraturtle said:

Because the pre-conditioning power comes only from the battery's DC output, and is not capable of bypassing the charging circuit to use the EVSE's AC output. At high battery states of charge, the charging system protects the battery by limiting current to less than 1 kW, regardless of the power demanded from the battery.

Click to expand...

Oh I'm confused again? Mainly because during pre-conditioning the car draws as much as the UK EVSE can deliver (10 amps), even though the car battery is close to 100%.

Bill

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Then again a 7kw Uk EVSE should be able to draw about 16 amps.