Heat Pump V REx

Hi all,

I've just been reading a few posts in one subject about the Heat Pump, but this feels like a slightly separate matter to the original subject that was being discussed.

It seems, the heat pump in the the non-REx versions will go where the 65cc motor goes in the REx versions. Therefore, the REx cars can't have a heat pump.

I'm struggling to comprehend the heat pump itself though. Does it warm the batteries and electric motor to the optimum temperature for longer range or does it warm the cabin on cool days before you get in (via the iRemote App)?

Personally, I'm looking for a REx version so the optimum heat for range is useful, but not essential. However, the ability to warm the cabin on cool/cold days would be lovely and one I wouldn't want to miss out on be cause I bought a more expensive REx version.

Any thoughts/comments/clarity would be VERY welcome!

The heat pump is an option, which replaces the less efficient resistive heater. I would love to have it on the REx trim, as it helps increase the electric range through its efficient operation, but it's not essential. As others have argued, the heat pump will not be necessary on the REx trim, because you will never be hard-pressed to extend your range as much as possible.

How about an extra storage compartment for non Rex an non HP i3s? Would be useful for shopping trips - must be enough room for a case of wine in there! or accessories like emergency / break down kit.

ecoangel said:

How about an extra storage compartment for non Rex an non HP i3s? Would be useful for shopping trips - must be enough room for a case of wine in there! or accessories like emergency / break down kit.

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When the REx unit is not there, there are support braces in the void for added structural support. When the REx is there, it's mass provides the added support in the case of a severe side impact in that area. It's not as simple as just keeping that area empty and creating small compartment with a lid to store things in.

as shown well here

That's a serious bracket!

Shame the space couldn't be used on non Rex / HP cars ....... but in reality how many of those will there be?

Parker said:

That's a serious bracket!

Shame the space couldn't be used on non Rex / HP cars ....... but in reality how many of those will there be?

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Well, there will be at least one in Hertfordshire!

Thanks Tom, looking at the structure I don' t think that's for side impact protection as such but it would add rigidity to oppose body roll as well as deal with that angular momentum from a 12,000 rpm Motor. Crumple zone would be provided by the existing ally cross members.

My point was the designers could have used the storage around that strut. Looks to be room for two more batteries.

The REx also has fuel tank under front seats so maybe there's even more space up there for pure EV model.

Most people don't know it but the A2 has storage below the passenger and driver footwells (originally designed for EV batts), under carpets and below boot next to battery space.

ecoangel said:

Thanks Tom, looking at the structure I don' t think that's for side impact protection as such but it would add rigidity to oppose body roll as well as deal with that angular momentum from a 12,000 rpm Motor. Crumple zone would be provided by the existing ally cross members.

My point was the designers could have used the storage around that strut. Looks to be room for two more batteries.

The REx also has fuel tank under front seats so maybe there's even more space up there for pure EV model.

Most people don't know it but the A2 has storage below the passenger and driver footwells (originally designed for EV batts), under carpets and below boot next to battery space.

Click to expand...

You won't see BMW doing anything like that with batteries though. My ActiveE has a battery system like that but it's a test car and BMW has learned you can't just put batteries wherever there is spare room. It's inefficient, costly and creates more things to break.

Like the Tesla Model S, BMW is using the 'skateboard' design with a central battery in one large case located under the drive module. This is the best way to manage the battery system, especially for cooling and heating. Having separate, smaller battery packs placed wherever they could fit them is a very poor design and reduces efficiency. One of the things that got me so excited about the i3 was the approach BMW took. That the purpose designed and built EV would have the proper architecture. If they started sticking battery modules here and there just to get more range they would lose my sale for sure.

I would be opposed to such battery placement as well. While I agree that space should be used efficiently in a small vehicle, I don't think that any valid or worthwhile idea has been brought forward. We have seen LEAF owners shoehorn a spare wheel into some unused space designated got wireless charging in the same general area. Perhaps better and more viable ideas will sprout once the i3 is in owners' hands.

Space is space, whether it should be used for future upgrades to battery capacity depends on access, weight and balance and crash worthiness.

NB: the REx weight at the rear is "balanced" by having a fuel tank right under the front seats - something that the Lancia Delta S4 supercharged and turbo charged Group B rally car featured and which was subequently condemned as a poor design feature. This model of the Delta had a Carbon Fibre body mounted on a space frame: http://rallylegendreplicas.com/Lancia_Delta_S4.html

Of course the i3 is not going to be driven in the same circumstances as those competition machines but it bears consideration that in the REx i3 you are effectively riding on a gas tank at 60 mph with some heavy batteries behind it.

ecoangel said:

Space is space, whether it should be used for future upgrades to battery capacity depends on access, weight and balance and crash worthiness.

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Yes, that's a good start, but the list is not exhaustive. I would include other considerations in that list as well. Such as, how difficult is it to temperature-manage batteries in this location, and also impact on reliability. You will need to run sensors and other wiring back there, and depending on the amount of vibration and other stresses, this just might not be the best spot to "stuff more batteries into". While we like talking about these things, and I totally appreciate the amount of passion going into these vehicles, please keep in mind that very few people on these boards have any real-world experience with creating and validating automotive designs. Yes, there might be some who have done a conversion, but these are often not crash-tested, don't have to be maintained and built on a large scale, to give reliability and serviceability a strong consideration. As I mentioned above, I don't think that the space designated for the REx is a particularly good spot to install more batteries into. Following that logic, we could ask for more batteries to be installed in the frunk also. That said, I'm all for efficient space utilization and mentioned that above as well.