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Discussion Starter #1
Looking for some help with my learning curve.... I understand that you can't have an i3 with a REX engine and a Heat Pump as they would occupy the same space beneath the boot floor.

So if you choose an i3 REX how does it heat the cabin in the middle of winter? Does it use a convector heater like the Mk1 LEAF or some other method?
 

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Yes - I think that's right. It would be better if it did use the Rex engine to generate heat. As it is, the heater will significantly reduce EV range like it does in the MK1 Leaf.

I believe it is an electric heater like the mk1 Leaf. It does not use the Rex to generate heat.
 

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Discussion Starter #5
I don't believe it spins up the engine just to generate cabin heat with a fully charged battery.
 

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The Ampera can use its Rex to heat the cabin, but will obviously not do so if driven in EV mode. I also believe that the Rex in the Ampera can provide drive directly. I think the arrangement in the Ampera is much more complicated than in the i3, where the Rex only ever operates as a generator.
 

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It uses the same electric resistance heater as comes standard on the pure EV i3. A heat pump is optional only on the pure EV version.

The heat pump does NOT go in the same spot as the range extender motor. The system doesn't use a second compressor for heat. There are valves that put the aircon in reverse. There may have been some plumbing issues elsewhere.


The main reason is that BMW didn't think anyone would want the expensive heat pump on the Rex version since they have the range extender.
 

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The i3 Rex motor is off most of the time. It is also small, producing 25kW peak. Running it at full power would probably deliver less waste heat to the car then the electric heater. Heating the car that way could well use up more range then using the battery. And you are running an ICE motor when maybe you wouldn't need to at all.



There is also the problem of where to dump 25kW of power if the battery is full. At idle, the rex isn't going to generate much waste heat.

Our van has a 45kW motor. The heater never warms up at idle. Even on level ground it takes forever. The van needs to climb a hill before the heater is really warm enough.


I'm not an automotive engineer but not all of the waste heat is going to end up in a heater radiator. Engines dump some of their waste heat into the exhaust and the oil. More is radiated out through the engine casing.
 

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Discussion Starter #11
Link just shared with me via Facebook: https://db.tt/Kn1KEeW1

In particular this explains it brilliantly:

Screen Shot 2014-08-06 at 12.14.57.png
 

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Discussion Starter #12
Am I the only one thinking I would like the OPTION of a Heat Pump on the i3 REX version so that I can use MORE of the battery in winter rather than decimate the range with 5.5kW being used to heat the car and quicken the REX generator burning dino juice?
 

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5kw of heat would warm the cabin very quickly. I can't imagine that the heater will run at that power for very long. Even at low temperatures, I would have thought that 2kw would be quite enough.
 

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In the Gen1 Leaf the consumption drops rapidly from aroud 4.5kW as the car heats up and I've rarely seen more than 2kW when up to temperature. 5.5kW continuous would roast you (or certainly me) here in the UK. We run our whole 4-bed detached house on 6kW!
 

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Not having run the Ampera in winter yet, but I'm wondering if the i3 also has heated seats. Particularly if there's just you in the car and unless it's sub zero outside, might it be best to just wear something warm and put the heated seat on?
 

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Winter pack??? For the UK???? Are they the automotive equivalent of Ryanair?

I always used to joke that BMW would make the steering wheel an optional extra if they could. I'm thinking that my decision to go for the Ampera over the i3 Rex was more than a £5k saving when you look at the specs like for like.
I'm still going to be very interested in a used one second hand for my next vehicle, so I'll need to research what extras I'll need to be looking for.

Anyhoooo I'm off topic! Sorry...:oops:
 

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In the Gen1 Leaf the consumption drops rapidly from aroud 4.5kW as the car heats up and I've rarely seen more than 2kW when up to temperature. 5.5kW continuous would roast you (or certainly me) here in the UK. We run our whole 4-bed detached house on 6kW!
But your house must have decent insulation to keep heat losses down. A thin-walled box on wheels with single glazing leaks heat like a tent.
 
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