Heater?

[Fisher99]

I've been trying unsuccessfully to find out about the heater in my 2014 i3/REX. I assume this is a resistance type heater? If so, does anybody know the wattage? Does it just heat the air? Or does it heat a water circulation system of some sort? I used it for the first time the other day and it seems to really impact battery life. Possibly even more than running the A/C.

 

[alohart]

It's all explained in detail here. Both the BEV and REx have resistance heaters that heat circulated coolant that passes through a heat exchanger that transfers heat to the cabin air. However, North American BEV's include the heat pump option that is used for cabin heating until it is so inefficient due to very low ambient temperature that the resistance heater turns on. The resistance heater uses considerable power as you've noticed.

 

[jadnashuanh]

The seat heaters are sometimes a more efficient method of keeping warm versus the cabin heating in the REx. The heat pump on the BEV is probably in the order of 3-4x more efficient which is one reason why it has a better MPGe, the other is that the REx is heavier by around 350#. If you can set a departure time with cabin preconditioning, that can take the bite off when it's cold. You need to be plugged into an EVSE to make that more efficient, though, at least in range available.

 

[Fisher99]

So if I am understanding correctly, my North American 2014 i3/REX uses a heat pump to provide heat. At least until some pre-determined temperature when it decides that it can't extract enough heat so it turns on resistant heat? If that's the case, since the outside temp was in the mid 50's, I would assume that it was using the heat pump when I turned the heater on. If it was draining the battery that quickly using the heat pump I shudder to think what using resistance heat does... Our temps are regularly in the 30's and 40's in the winter, with a few weeks that dip into the 20's and even teens. That's going to take a big bite out of my range.

Good tip about pre-conditioning the car before leaving home and while it is still connected to the L2 charger. And about using the heated seats instead of cranking the heat up.

 

[Fisher99]

Hmmm... After perusing the document provided by ALOHART, it looks like my assumption was incorrect. Since I have the REX, it looks like all heat is supplied by resistance heating which heats a water loop which then provides heat to the passenger compartment via a heat exchanger. Almost seems like it would have been more efficient to just have the resistance heat do the heating of the passenger compartment directly, but I suppose BMW knows what they were doing, so this must be more efficient. I didn't see anything in the document that says how much juice the resistance heater draws, but it must be fairly significant. Wonder why they didn't use the heat pump in both the BEV and REX versions of the i3...

 

[alohart]

Wonder why they didn't use the heat pump in both the BEV and REX versions of the i3...

The BEV's heat pump implementation uses the A/C compressor but switches the front and cabin heat exchangers using clever plumbing so that the front heat exchanger takes heat from ambient air and the cabin heat exchanger adds this heat to the cabin air when in heating mode and the cabin heat exchanger extracts heat from the cabin air and the front heat exchanger transfers this heat to ambient air in cooling mode. Because of the REx fuel tank, there isn't enough room for the additional plumbing needed for the heat pump.

 

[gt1]

Almost seems like it would have been more efficient to just have the resistance heat do the heating of the passenger compartment directly, but I suppose BMW knows what they were doing, so this must be more efficient.

The direct air heaters operate at much higher temperatures. Anything combustible is ingested in the system could lead to a fire.

 

[Fisher99]

Wonder why they didn't use the heat pump in both the BEV and REX versions of the i3...

The BEV's heat pump implementation uses the A/C compressor but switches the front and cabin heat exchangers using clever plumbing so that the front heat exchanger takes heat from ambient air and the cabin heat exchanger adds this heat to the cabin air when in heating mode and the cabin heat exchanger extracts heat from the cabin air and the front heat exchanger transfers this heat to ambient air in cooling mode. Because of the REx fuel tank, there isn't enough room for the additional plumbing needed for the heat pump.

Makes sense. Thanks.

 

[Fisher99]

The direct air heaters operate at much higher temperatures. Anything combustible is ingested in the system could lead to a fire.

I suppose that's a possibility. But seems like BMW's engineers could fairly easily mitigate that risk.

 

[jadnashuanh]

I've said it before, but it appears that the REx version was forced on the engineers by the marketing division. As a result, it didn't get as much attention as the BEV. Given that with the newest batteries, BMW has stopped making the REx version available in at least some markets, the reality of the needed range for the design has caught up. I don't think that they'll put that much more effort towards optimizing the REx. It is what it is. If there's ever a replacement for the i3, it will likely just have even better batteries, without a range extender. It was designed as a city/commuter car, not a replacement for 'all' vehicles. The fact that it can, but with limitations, is a tribute to the engineers.

 

[jfran2]

I also have a 2014 Rex model, and live in the Midwest where it was in the teens and 20s for most of last winter. I always preconditioned the car in the morning, kept the heat at 66 and used the seat heaters a lot. I stayed reasonably comfortable, if not exactly toasty, and usually had only a small effect on my range - 7 or 8 miles. Anytime I was on the highway, I'd turn on the Rex and give myself a few more degrees of heat! Ah....

 

[vreihen]

My commuting vehicle for the last 9 winters was a diesel pickup truck, with a 1,200 pound lump of steel under the hood that wouldn't even move the temperature needle during my 10-mile commute on cold mornings. I'm looking forward to having heat this winter!!!!! :lol:

 

[Fisher99]

Well, it will be interesting to see how the winter goes. Of course if this thing is as bad in snow as I am being led to understand, it may end up sitting in the driveway while I am driving my (diesel) 4x4 Ram. Fortunately we usually only have a few weeks of snow.

 

[vreihen]

My impression from what has been written so far is that the i3 does pretty good in the snow for a RWD car with anything but the summer-only Ecopia (600?) tires. The skinny tires and weight of the battery pack should help it to sink down to the pavement, and not float on top of the snow like wide tires (or snow shoes).

Now, whether the people writing those winter articles also had driven a 4x4 Ram Cummins to compare snow performance against one is a different story. I don't know about your truck, but mine hasn't been stuck or even inconvenienced by 2+ feet of snow during any east coast storm over the past 10 years. The only painful thing about driving it in the winter is cleaning the snow off of what seems like 5 acres of truck after every storm.....

 

[gt1]

Why they don't offer a heated steering wheel is beyond me.

 

[jadnashuanh]

Why they don't offer a heated steering wheel is beyond me.

Precondition the cabin, who needs a heated steering wheel? They sweated grams in the design and optimizing efficiency. You then might ask why the heated seats...they're more efficient warming you if you choose to keep the cabin temp lower.

FWIW, winter tires on the i3 make it a decent car in the winter. Given a choice today, the Nokian R3 winter tire would be my choice versus the OEM Bridgestone. From what I can find, those are the only two manufacturers that make a winter tire designed to fit the i3, especially when you consider efficiency as part of it.

 

[vreihen]

Is there something wrong with Blizzaks, other than that they seem to be old stock and possibly out of production in i3 size? I will probably go Nokian in the fall, but have run Blizzaks on every one of my other vehicles for years.....

 

[Fisher99]

Why they don't offer a heated steering wheel is beyond me.

Amen!

 

[Fisher99]

Unfortunately (or fortunately, depending upon how you look at it) my i3 has the 20" wheels which means that I can only use the summer tire. Not even an all season tire available, let alone a true winter tire. And I hear that the summer tires are useless in the snow.

Maybe if I load a couple hundred pounds of lead into the rear hatch...

 

[Fisher99]

My impression from what has been written so far is that the i3 does pretty good in the snow for a RWD car with anything but the summer-only Ecopia (600?) tires. The skinny tires and weight of the battery pack should help it to sink down to the pavement, and not float on top of the snow like wide tires (or snow shoes).

Now, whether the people writing those winter articles also had driven a 4x4 Ram Cummins to compare snow performance against one is a different story. I don't know about your truck, but mine hasn't been stuck or even inconvenienced by 2+ feet of snow during any east coast storm over the past 10 years. The only painful thing about driving it in the winter is cleaning the snow off of what seems like 5 acres of truck after every storm.....

Yeah, it's hard to stop the Ram in the snow. As long as you don't get into the really soft deep stuff, and then 1,100 lbs of Cummins engine isn't your friend...