Energy Consumption During Preheat

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jamie94bc

Well-known member
Joined
Dec 29, 2013
Messages
125
Location
Hampshire, UK
Does anyone know how much energy (approx. in kWh) the preheat process consumes? I know this is going to vary depending on the ambient temperature etc. Might try to watch my OLEV meter tomorrow morning.
 
As you say it really depends on how cold it is outside or whether you park under cover / in a heated garage!

I'd say anywhere between 2 and 10 kWh with pre-conditioning just before you need the car.
 
I have the car for a week now, and i noticed something strange. I have a sensor which logs the power usage from the house. The car was programmed with 05:12 as departure time.
I woke up at 4:40 because of the noise my charging station makes: 3 clicks. I heard the car heating up when i was preparing to go out. It's not a lot of noise, but i can hear some fan's.
Now i am looking at the log, and i see the power is not taken from the house/charge unit until 05:12!!! I left at 05:15.

Can anyone look into this to see if they experience something likewise?
I also notice that the predicted mileage in the car is lower than one shoud expect with preheated batteries.
 
I have similar questions?

I have noticed that at times the preheat actually decreases range and hence must be using battery power rather than mains power.

If you manualy request cabin preheat from iRemote then it appears to use battery power too.

I am also puzzled as to what is happening with the battery during preheat? There are no options to control this function.

I have the winter pack and heat pump.
 
It seems absurd if battery power is depleted to pre-heat the cabin while the car its still connected to a mains supply.

I guess if it was parked outside in a cold climate, you could spend all night fully charging the battery - and then lose 50% of your range in an hour's cabin pre-heating.

Hopefully this is just a correctable software glitch.
 
I wonder if this explains why when I get into my car in the morning at about the time I have set it to be preconditioned (with the car plugged in having received an overnight feed) I never see a full charge - there is always a bit of blue missing from the charge bars.
 
Stevei3 said:
Hi Guys,

my guess this is because the preheating draws more power than the plug provides.

Steven
This is what happens on the Leaf using the supplied EVSE charger (10A). But a 16A or 32A supply from a wallbox or equivalent is (I'm told) enough to satisfy the heating requirement without depleting the battery. I guess the i3 will be similar,
 
OK, i had the opportunity to observe this some more seriously today.
Departure tim was set to 6:30.
I was watching the power from my house using a sensor on the power meter of the house installation. So all of the power is measured by the sensor. I can follow the readings on my laptop.

I hear noise at the car from about 6 o'clock. The power usage from the house remains unchanged untill 6:19. I assume the heating of the battery has already begon much earlier when i hear the first noises.
Power went up to almost 4000 Watt untill i left at 6:30.

My charger can supply 16A, i do not expect the charger causes this behaviour.
The weird thing is that it nog consumes power from the house, while it seems to be heating up untill 9 minutes before departure.

I will observe this some closer as soon as i can.
 
We had an i3 BEV last weekend for a 24hr test drive (my wife's arrives in July, we needed to test it on a rather steep drive).

I configured the pre heat to come on for Sunday morning... the car had charged overnight and was plugged into a 32A charging point in the garage...

The car was preheated as expected, however we both noticed the charge was slightly down from 100%...

I didn't make the connection at the time... however reading this thread I now think the preheat was responsible...

And this is despite the car being plugged into a 32A charging point all the time...

If this turns out to be the case... that is VERY disappointing...
 
This is what I found in the Dutch manual:

"Door het voorverwarmen tijdens het laadproces kan de maximale actieradius bij het wegrijden ter beschikking gesteld worden."

Google translate (sorry, bit lazy today...)
"By preheating during the charging process, the maximum range when starting disposal can be made"

It seems that it takes the current from the charger only during the charging process.
 
Preheating heats the battery as well as the cabin I understand. If the battery temperature is higher than it was after full charging earlier in the night it can accept more charge so the state of charge may appear lower. But the available range may well be more.
 
Today i checked my findings sofar. All the same.

When the battery was at 100 percent i turned on preheating manualy via the connected drive website. The car immedeatly started to take power from the charger. (at work so other charger)

Next step: turn off the cabin preheat, but leave the departure time on. I assume it's gonna heat the battery, and the interiour unheated then. Then i am gonna look at the behaviour of the power flow again.

Can anyone copy my findings somehow
 
I checked the power meter this morning.
1) Car showed 100% charged in iRemote app and it was not using any power from the outlet
2) Started the preheat through the iRemote app
3) Fans started and power meter immediately showed about 1.5A (220V)
4) A few seconds later it went up to maximum current (I would think to top up the batteries)

Just like one would expect.
This was on a BEV with heat pump in Stockholm with about 6 degrees Celsius

If you are new to the i3 or is thinking of buying one read more about some of the smart functions here
http://bmwi3owner.com/2014/02/winter/
 
bmwi3ownercom said:
I checked the power meter this morning.
1) Car showed 100% charged in iRemote app and it was not using any power from the outlet
2) Started the preheat through the iRemote app
3) Fans started and power meter immediately showed about 1.5A (220V)
4) A few seconds later it went up to maximum current (I would think to top up the batteries)

Just like one would expect.
This was on a BEV with heat pump in Stockholm with about 6 degrees Celsius

If you are new to the i3 or is thinking of buying one read more about some of the smart functions here
http://bmwi3owner.com/2014/02/winter/

Where did you read the power consumption? Did the app/car show this or do you have an Amp meter at home?
 
Unfortunately I don't believe there is anything wrong with your cars; I believe this may be how it is designed to work.
I say so because this is how it work's on our ActiveE's. When preconditioning initially begins, the draw is from the battery and doesn't pull energy from the EVSE until the state of charge drops a percentage or two. Once the SOC is down to 98%, the car signals to the EVSE that it needs power and it turns on until the SOC reaches 100% and it then turns off again, even if the preconditioning is still ongoing. It cycles like this the whole time and I have noticed during a hour long preconditioning session the EVSE can turn on and off quite a few times. If you happen to time if right, you do have a fully charged battery and a fully preconditioned battery and cabin, but it's really just luck if the car ended preconditioning just as it became fully charged. Me and the other ActiveE drivers would wonder what sometimes the car would be fully charged and why other times we would get in and it would say 98% charged after preconditioning until we figured out how it was working.

However this is while plugged into an EVSE with a 32 amp, 240v supply. If the supply is lower, the EVSE will remain on for longer periods as it takes it longer to get the battery back to 100% at with point it will shut off. Here in the US, we also have 120V and while preconditioning off of 120V supply, the cars draw is more than the supply so the car will never shut off. Instead it will continue to run down the battery. The good thing is, the car recognizes it is plugged into a 120V supply and cuts the preconditioning session shorter than usual because it figures the owner doesn't want to use too much battery.

I'm with you guys and don't like this, but your car isn't' *broken*, it is working as designed even if the design isn't perfect. This is one of the things that bothered me about my ActiveE and I included a lengthy explanation of this in my reports to BMW with the hope they would correct it for the i3. It appears my suggestion was ignored. :x What do I know anyway?

BTW, this is another reason to WANT a proper state of charge gauge as I have been a proponent of. You can then see exactly where the SOC is when you get in the car instead of it just "looking a little down form 100%".
 
Everything seems to be pointing the way of your explanation Tom...

In which case that's a shocking piece of design/engineering from BMW... especially on a car designed from scratch to be an EV.

Not something that would stop us getting the car of course... but horribly disappointing none the less..

I'd like to this it was something easily fixed in software... but given your feedback and the lack of correction... I am guessing it is not..

Such a shame..
 
VintageMark said:
Everything seems to be pointing the way of your explanation Tom...

In which case that's a shocking piece of design/engineering from BMW... especially on a car designed from scratch to be an EV.

Not something that would stop us getting the car of course... but horribly disappointing none the less..

I'd like to this it was something easily fixed in software... but given your feedback and the lack of correction... I am guessing it is not..

Such a shame..

I think it *may* have to do with not overcharging the batteries which could damage the cells. I suspect the way the car is designed, the power for everything always comes from the battery, so If the car is 100% charged and you activate the wallbox (EVSE) it could over charge the cells a bit so BMW wanted the state of charge to drop to ~98% before the car draws power from the mains again.
 
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