@bruce - The reputation of Li Ion batteries is that of power tools, mobile phones, laptops etc. I am no expert but I do know that the chemistry is different in cars and they have very different charge/discharge characteristics and lifespans. They also have complex battery management systems. You really cannot consider the batteries used in EVs in anything like the same way.
I don't know about that lawsuit but Nissan's attitude and advice has softened since the launch of the Nissan Leaf because of their experience gained. They were suggesting that regularly charging above 80% was going to overly reduce the life of the battery. The same with rapid charging. However, they have found that their caution, although based on their expectations at that time, were rather excessive. They now say that they expect there to be 80% of new range at 5 years and 70% at 10 years. Even 70% will be adequate for most so I don't see many people wanting to overhaul their batteries at all during the life of the car.
However, the life of the EV batteries are likely to be reduce through rapid charging and charging over 80%... just not anything like as much as was first thought. So now I don't worry at all about doing either. I still only charge to 80% as a matter of course but will always charge to 100%, or rapid charge the Leaf if I want/need to. As dpeilow says... the ideal is to keep it around 50% but with limited range overall that is not practical for most people.
A lot of EVs have active battery thermal management. The Leaf rather unusually doesn't and that is why there are some issues with the battery lifespan in very hot countries. Nothing kills batteries more than heat and Leafs that were bought in very hot locations such as Arizona are seeing very much shortened lifespans. Nissan has accept responsibility though and is replacing them under warranty.
@proddick Personally, I don't see the BMW i3 as having the opposite problem because I see the i3 as a full B-EV, similar to the Nissan Leaf, but with a range extender for the times you cannot find a charging location or if a charger fails. In reality, because of the 90+ mile range and the rapid charge capability, it is very possible that the majority of i3s won't use their range extenders hardly at all or even ever. Many Leaf owners are getting by quite happily doing long trips without the range extender and so can the i3... it just gives a degree of insurance. I don't think the REX on the i3 is intended for continuous use in the same way the generator is on the Ampera. We only need the higher petrol capacity because the Ampera does not have the battery range. It the Ampera had a battery range of 90+ miles and rapid charging then there would be no need at all for a 300 mile petrol range.
I think that BMW has it about right with the current state of the art. I didn't say that when they first announced the i3 and then I said the same as you but I now realise that the more battery range you have the less petrol range you need... just to get you to the next charger or home really. Obviously in places where there are few chargers then the Ampera would be more suitable but with the increasing rate of development of charging infrastructure I can see the Ampera as a very much an interim solution and I suspect that there may not be much of a market for it once the BMW i3 and similar EVs with 100+ mile range and range extenders take hold. I don't see many people wanting an EV with just 40 miles range when there is a viable and useable charging infrastructure... and we nearly have that now.
Then it is worth remembering too that all range extenders are really only necessary because EVs don't have the range or speed of charging right now and that the charging infrastructure is still being installed. By the time the more affordable generation 3 Tesla is launched in 3-4 years the infrastructure will be much better and the battery and charging tech will have moved on. It is very possible that within 5 years from now range extenders of any description may well not be considered necessary and EVs will have 200-300+ mile real world range and rapid charging. Then the likes of the Ampera and BMW i3 with REx will look rather old-fashioned!!!
