BMW i3: How Preconditioning Works

MAR 16 2015 BY TOM MOLOUGHNEY 20

Setting the preconditioning feature from the i3's iDrive is simple, but not as intuitive as I believe it could be. You can set the time of departure for every day of the week and the i3 will be charged, preconditioned and ready, provided you're charging from a proper 240v, level 2 electric supply.

Setting the preconditioning feature from the i3’s iDrive is simple, but not as intuitive as I believe it could be. You can set the time of departure for every day of the week and the i3 will be charged, preconditioned and ready, provided you’re charging from a proper 240v, level 2 electric supply.

In many ways electric cars are very similar to their internal combustion counterparts and that’s by design. Most major OEMs are afraid to make something that’s “too different” from what their existing customer base is comfortable with. However there are features in electric vehicles that are indeed drastically different. The first one that comes to mind is regenerative braking which allows the electric motor to convert the vehicle’s kinetic energy back into electricity which in turn recharges the battery. This feature changes the driving dynamics of the car (some more than others depending on how aggressive the regenerative braking system is) and the operator needs to adjust to this when they first transition to an electric vehicle.

During the winter months preconditioning in New Jersey not only means getting into a warm car in the morning, but it also adds valuable miles to the car's range by warming the battery cells up to their preferred operating temperature.

During the winter months preconditioning in New Jersey not only means getting into a warm car in the morning, but it also adds valuable miles to the car’s range by warming the battery cells up to their preferred operating temperature.

Another unique feature most modern electric vehicles have is the ability to precondition (warm or cool) the high voltage traction battery as well as the passenger cabin. This allows the driver to begin their journey with a properly heated or cooled battery and cabin, while still having the state of charge at or near 100%. Some conventional combustion cars also allow you to remotely start the vehicle to warm it up in the winter or cool it off in the summer, but the reasoning behind that is purely comfort-driven, and with EVs it goes beyond that. Since electric vehicles have shorter range and longer refueling times than their combustion counterparts, it’s important to save the energy in the battery for its main purpose; to propel the vehicle, and not waste too much of it on ancillary power draws.

*Editor’s Note: This post appears on Tom’s blog. Check it out here.

Warming the battery and the cabin uses a lot of energy, and doing so while the vehicle is plugged into the main power allows the driver to begin their trip with a properly warmed battery (which will increase the range) and still have a fully charged pack. This is very important for EV owners in cold weather climates. It is also useful to cool the car in hot ambient temperatures, but more frequently used by EV owners in the cold since a cold battery can reduce its range up to 30%. A hot battery won’t reduce the car’s range, but it can have an adverse effect on the longevity of the battery cells. Therefore preconditioning the battery in very hot climates is also advised, but for different reasons than doing so in the cold.

During the day my i3 is parked outside while I work. Accessing the preconditioning from my iRemote app is very useful as I don't have to go outside to the car to turn it on.

During the day my i3 is parked outside while I work. Accessing the preconditioning from my iRemote app is very useful as I don’t have to go outside to the car to turn it on.

OK, so it’s clear preconditioning is useful, but do you really know how it works on your i3? I’m afraid most i3 owners don’t. In fact, judging by how many people have messaged me this winter asking for help with preconditioning, I’m thinking it’s right up there with how to properly care for their battery as the top misunderstood items of i3 ownership. This is all new stuff, and even most dealers don’t know all of the answers so it’s no surprise the customers are a bit confused. This post should clear the air on most questions about how preconditioning works on your i3. I knew how most of the i3’s preconditioning worked, but just to make sure I didn’t have anything confused, I reached out to BMW’s top electric vehicle technical services manager in the US to get answers to direct questions that I had previously received from readers:

Q. When Preconditioning via the iRemote app Remote Control menu is activated, only the cabin is preconditioned, not the battery, correct?
A. When triggering Preconditioning from the Remote Control menu, the answer is Yes, only the cabin.

Q. If you want to precondition the battery from the app, you need to set the departure time and then enable “preconditioning for departure,” correct?
A. Yes, provided the departure time programmed is at least 3 hours from the time when it is selected.
*Important: This is a very important fact that most i3 owners are not aware of. If you don’t set the departure time at least three hours in advance the car is not performing battery preconditioning at all, only the cabin will be preconditioned.

Q. Can you precondition the battery without the vehicle being plugged in?
A. The HV battery, no. The cabin, yes.

Q. Can you precondition the battery while the vehicle is plugged into a 120v source or does it need to be connected to a 240v source?
A. 120V (Level 1/OUC) or 240V (Level 2) have the same effect in terms of Preconditioning. However, if charging on Level 1, the preconditioning consumption is higher than the charge rate, therefore potentially the vehicle will not be fully charged at the departure time.

Q. How early before the departure time will the vehicle begin to precondition?
A. When using the vehicle preconditioning menu, it will depend on temperature, but generally 30-40 minutes prior to the set departure time the cabin preconditioning will start, and the battery preconditioning will start 150 minutes prior to that.

Q. Will the car ever turn a battery warming on by itself if the battery temperature gets critically low. For example, the car is parked outside and plugged in and the battery temperature drops below 30 degrees, will the preconditioning turn on and warm the battery up without owner intervention?
A. No. User intervention is required for battery preconditioning. If the battery temperature is very low, it will be outside its normal operating temperature. As a result, the power output and usable energy of the battery will be reduced.

Q. How about if it gets critically hot – over 105 degrees?
A. If the battery temperature is higher than the optimal operating range and preconditioning is activated, the battery can be cooled. This is not very common due to the fact that the battery is such a high thermal mass, is located close to the ground, and is not exposed to direct sunlight.

Q. Why is it that sometimes after preconditioning (plugged in) the car is left at 97% or 98% SOC? Why doesn’t it fully recharge the car to 100%?
A. When preconditioning using a Level 1 charger, the car will always be below 100%. It could be about 80% or lower.(Because it uses more energy than the 120v source can provide) When using a Level 2 charger, the SOC could be slightly under 100% as the vehicle electrical load stays somewhat constant while the charger will switch off and on.

Q. Will battery cooling occur automatically while you are driving when the battery temp exceeds a certain set point?
A. Yes.

Q. When battery preconditioning is being performed, what is the battery temperature that the vehicle is attempting to achieve?
A. The battery is warmed or cooled to bring it close to or within the optimal operating range of 25-40C (77-104F)

I’m certain that the vast majority of i3 owners are not aware that the car does not initiate battery preconditioning unless they set the departure time at least three hours in advance. Also, based on feedback I’ve received here, many i3 owners aren’t aware that they aren’t preconditioning the battery if they initiate precon by pressing the small fan icon at the bottom of the main state of charge screen on their iRemote app. By doing so, that only initiates cabin warming or cooling. In order to precondition the battery as well as the cabin from the app, you must set a departure time at least three hours in advance and then slide the preconditioning tab to “on.” Don’t feel bad if you own an i3 and didn’t know all this, most client advisers at many BMW dealerships don’t know it either. It’s a little confusing at first, and honestly I think the app could be made a little more intuitive, but once you understand how it works, it’s easy to set. You can also set the departure times and precon from the iDrive in the car itself but you need to first set a departure time and activate Low Cost Charging (Even if you don’t actually use TOU low cost charging).

ScreenshotPreCon1

Using the “Activate Climate Control” app feature on the left only preconditions the cabin. To precondition the battery as well as the cabin, use the “set departure time” feature which is accessed by pressing the small clock tab on the top right of the state of charge display screen. Once you set the departure time, you also need to slide the precondition tab to the “on” position.

ScreenshotPreCon2

Using the “Activate Climate Control” app feature on the left only preconditions the cabin. To precondition the battery as well as the cabin, use the “set departure time” feature which is accessed by pressing the small clock tab on the top right of the state of charge display screen. Once you set the departure time, you also need to slide the precondition tab to the “on” position.

Living in northern New Jersey I get to experience a range of temperature extremes and using the preconditioning feature is definitely helpful. We just finished the coldest month I can ever remember and it seemed just about every day I was leaving the house in the morning with temperatures in single digits or below zero. One day it was actually minus eleven degrees Fahrenheit when I began my morning drive. Even though my car is parked inside my garage, when it’s this cold the battery temperature drops to levels that severely impact its performance and the range is reduced. I noticed I could add as much as eight to ten miles to my range if I used the preconditioning on the coldest days. It’s also nice to get into a warm car, and this enables you to turn down the cabin heat a bit, which additionally helps extend the range. I found that if I allowed the preconditioning to warm the cabin, I could then lower the cabin heat, or even turn it off for a while and just use the heated seats which use much less energy than the cabin heater.

I hope this helps i3 owners understand a little more about preconditioning. If you have more questions, please leave them below in the comments section and I’ll do my best to answer them.

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20 Comments on "BMW i3: How Preconditioning Works"

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Tom, do you know if the Leaf has a battery preconditioning option?

Thanks!

No. It will only enable a battery heater to prevent a no-start scenario due to frozen electrolyte.

The battery pack stays cold in the winter and bakes in the summer, and there’s nothing the LEAF does to condition the battery for optimal range.

You can, however, set the LEAF to pre-condition the cabin (~72F) based on a specified departure time. You can also kick on the climate control on the fly with the CarWings app.

I have noticed that preconditioning the Leaf does in fact warm the battery by one or two temperature bars. This is more an “accident” rather than by design. Of course, I should note that I have a 2012 Leaf with a 3.3kW charger, and a 5kW heater. At first, the heater will actually draw more power than the charger can provide. It gets the extra power from the battery. Then, as the heater levels off to about 1.5-2kW, it tops the battery off again. This little bit of discharge/charge current from the battery is enough to warm it up a little bit. It’s nothing like an actual TMS (as in the i3/Volt/Tesla/etc), but every little bit helps.

It begs the question, why did BMW require that the departure time programmed be at least 3 hours from the time when it is selected? It seems easy enough to trick the i3 to start preconditioning the battery by setting a departure time later than your actual expected departure time for when you forgot to set it and remember when you wake up in the morning. The battery won’t be fully warmed (conditioned) when you leave, but isn’t a partially warmed battery better than a stone cold battery on a frigidly cold morning?

Tom thanks for providing a detailed article.

1). Assuming the 3 hour thing, will the battery precondition on 110?

2). Have you noticed that the ‘range loss’ magically reappears should the battery be warmed, or is it gone forever?

3). What sizes (watts or BTU/hour) are the cabin heater, and the battery heater, if they are not one in the same?

Preconditioning should work for the battery as well as the cabin, like a Tesla. You are likely not to be plugged in at work and “warming up” the battery can really help on range as the region is limited until the battery warms up.

If you are not plugged in, you are going to use more battery power warming the battery than you are going to gain back in range. Therefore, it never makes sense to precondition the battery to extend range when unplugged.

There may be other reasons, though. For one, you will get less power out of a cold battery so preconditioning it will help your performance. The other case is to protect the battery itself – if the electrolyte freezes, the battery is toast.

Not alway’s the cas!
There a tradefoff between leaving a battery dead cold with all the energy in but that can’t regen or give full power without more loss.
And heating it just prior to get back on the road.
Beside that, one thing that would help probably better is to use the regen power to heat up the battery when it is to cold to accept any charge.
At least, the battery would welcome any heat.
Pretty easy to do it with any electric motor.

I agree completely that using excess regen to heat a cold battery is a great idea. It’s too bad that it’s just diverted to friction brakes instead (well, on most EVs anyway).

I’m not convinced that there is ever a case where using the battery power to heat itself would actually allow you access to more of the energy, and hence actually increase driving range. Remember that the battery will warm up a little anyway during use (thanks to internal resistance), so you would in theory get a little bit back once you hit the road.

Or fix the bugs in the software that prevent Regen from working at all in cold weather.

One Tesla tech explained to me the basic problem (he was from Green Bay). “Tesla people are mostly from California, and don’t try to understand about COLD too much.”

In my experience, most people who live in California do so because they cannot or will not tolerate the cold. “Cold” to them, by the way, is less than 60F. When I lived in Palo Alto, I got a reputation as the only guy insane enough to still wear shorts when it’s 50F outside. Meanwhile, my neighbor now broke out his shorts as soon as temperatures break above freezing!

It is interesting to see how quickly the various manufacturers do or do not adapt EVs to cold weather. It seems like in the first couple of years of EVs, the most progress was made in this area. Three examples that come to mind are the proliferation of heated seats, the addition of heat pumps, and the lowering of the Volt’s “ERDTT” (Engine Running Due To Temperature) set point.

Great article, very informative. Does anyone know if there is a similar post for the Volt?

I’m sure ClarksonCote would be glad to write an article… He seems to keep more on top of this stuff than most. All I know is that the car takes about 10-15% more juice to charge in cold weather, and that the battery will charge 5% or so higher if you remote start it, and then the remote start is stopped or timed out. This is for my 2011. GM must figure its ok to charge the battery a bit more since they figure you’re gonna drive off soon enough anyway. I’m guessing there is only one ‘electric water heater boiler’ in the car (to be used by both the battery and heater), since the battery, and heater can also be warmed by engine jacket heat. They gave me a 200 page owner’s manual and a coffee table glossy story book, plus a cheapie camera to take pictures of my volt which I’ve never used, (there are benefits for being one of the very first owners), but the thing I miss is there are several things about the car, since its somewhat unique in operation (at least it was in 2011 MY) that they could tell you how it worked.… Read more »

I’ll have to poke around on GM-Volt.com a bit. There’s been a few articles there detailing both 120V and 240V EVSE power draw with remote starts, etc. for maximizing range and starting with a topped off battery.

In the Volt, a remote start DOES condition the battery as well, as far as I know. This remote start is like the BMW’s in that it also preconditions the cabin. Coming back to a nice warm (or cool) cabin along with a heated battery are the two obvious benefits to a remote start in a Volt.

The Volt doesn’t have the ability to set a timer to have the vehicle warm/cool at a certain time, though. However, this is somewhat offset by the ability to remote start from your cellphone using the RemoteLink app, or any computer using MyVolt.com.

Just for fun my nephew put the app on his smart phone, and it is 10-20x faster than Myvolt.com and far more reliable.

myvolt.com is a joke. It was bad 4 years ago and still bad. Rather like the volt’s voice recognition system. It works for the mechanic’s voices everytime but will not work EVEN ONCE for me.

Agreed. I never use MyVolt.com, only my phone app. It’s great to remote start my Volt withou having to be within sight of it. 🙂