Parker said:
Bearing in mind the weight difference is this a concern .... or will it be an issue in the long term?
This is the stuff I'm struggling to get my head round at the moment.
Parker, I think that having a light-weight car in city traffic is going to make a significant difference in terms of handling. In that sense, I personally completely agree with some of these design decisions, including the usage of carbon fiber, highly efficient tires and aerodynamic wheels. What was saved in terms of battery capacity and weight, can be gained back in efficiency. It's going to be a wash in my opinion.
That said, while there are many people who find the LEAF and its range perfectly adequate, there are some who wish to have more autonomy. I know several people that have purchased a Model S as a result. Although I find it unwieldy and too large for city traffic or commuting, it's very attractive for road trips, especially since you can refuel for free at Tesla-provided superchargers.
If I had any feedback, it would be that BMW should consider offering a longer-range purely electric car. When you look at the cost and weight impact of the REx, a battery-only trim with about 30 kWh of capacity would seem possible, without adding more weight or cost than the REx. I think a surprising number of buyers would select this option, and many of those will opt for the smaller battery without REx today.
One of the problems BMW could have faced here is energy density. Adding 8 or 10 kWh to the pack would make it not just heavier, but also more voluminous. The good news is the capacity warranty. This will put a safety blanket under the performance of the battery and give buyers the assurance that the i3 will be able to perform at a certain level in the future. I would be careful and realistic when projecting the real-world range of the vehicle. Make sure that it can meet your use case when the battery has lost some capacity and when it's cold and rainy outside. If this is not the case, then I would consider getting the REx or explore charging opportunities.