Simon, does the vehicle itself in a give you information on the battery pack's capacity compared to the original spec
It probably would be a useful piece of information, both in price negotiation, and in a buying decision for a particular vehicle. No doubt a more detailed analysis could be available regarding the 'health' of individual cells, which may not show up in an overall capacity assessment.." a sort of EV buyers report. Maybe it's just too early for the AA to do this sort of thing but I could see the value of an independent report rather than believe what the dealer tells you
The Ion doesn't give you any kind of direct battery capacity/health indication unfortunately, it always shows a 100% charge after charging regardless of how much battery capacity degradation there has been. You just get less miles per bar on a degraded battery. The only way you could estimate it without additional tools is the range remaining figure after a full charge, however this is based on the average energy consumption over the last 15 miles, so can easily be fudged simply by driving the car slowly and carefully (say a constant 30mph for 15 miles) and then charging it back up, which will give an inflated figure.
To truly know the capacity you either need to plug in a Lexia, which will show overall pack Ah/hr capacity, and cell balance state, or a Bluetooth OBD-II dongle with the Android apps Canion or Evbatmon. (Both also work with C-Zero and i-MieV) Evbatmon gives a full easy to read battery diagnosis with both overall capacity and it shows graphically the cell balance state which will immediately make a faulty or failing cell obvious. Canion is free but Evbatmon is about £29 I think.
So with a small wireless dongle an a small android tablet you could quickly and easily plug that into a prospective car and get a battery report in a couple of minutes. I didn't have this available to me and whilst I could have taken the Lexia and plugged it in before purchase the circumstances around the purchasing would have made this difficult so in the end I took a punt based on the range remaining estimate after a test drive and confirmed after bringing it home with the Lexia that pack capacity is actually very good for its age.
On a Leaf there are two bar graphs on the display - one is a battery health gauge and one is a state of charge gauge. The state of charge gauge shows how much charge you have left since last charging and always returns to full when fully charging, and is therefore scaled to the current battery capacity. The health gauge beside it is an indication of the battery health vs a new battery, so once the bars on this start dropping this is an indication of battery degradation and loss of range. This is the gauge they're talking about in ads when they say it still has "full bars".
This gauge is a bit coarse and the first bar doesn't disappear until a significant amount of capacity loss has happened so there is an Android app called "Leaf Spy" which is the go-to tool to diagnose the capacity of the Leaf battery, it too works using a bluetooth OBD-II dongle. I think Evbatmon also works with the Leaf and many other models of car so may be a more general tool for checking the batteries of many EV's, and ideal for someone buying and selling EV's.
So yes, with the right tools which are not particularly expensive, it's possible to check the true health of the battery of most EV's before buying. (Assuming they'll let you plug in!) Once people become more comfortable with EV's I think that this sort of check will become common place, just like you would inspect other aspects of any car.
Yes pads and discs can last ridiculously long amounts of time on EV's due to regeneration. They only really get used to hold the car stationary or get used in emergency stops. For normal driving most of the braking is done by regeneration so its common for them to last 2-3x what they would on an ICE. Sometimes they actually have to get replaced not due to wear but due to rusting away through lack of use.
The Leaf in that article is a 2013 model - which I think was when Nissan introduced a revised (Lizzard) battery with improved chemistry which is supposedly a bit more robust in hot conditions. So that high mileage without much range loss would not apply to a 2011 or 2012 model, which IMHO should be avoided, as those very early ones were notorious for capacity loss.
I find the 2p/mile claim as a taxi very hard to believe - the Ion is known to be more efficient than a Leaf in terms of watt-hours/mile (in fact I think it still holds the record as the lowest energy consumption per mile of any EV, probably due to its small size and weight) and I've done my sums on the Ion and there's no way I could get down to 2p/mile except in summer and if I only ever charged at night using economy 7 - which clearly a Taxi cannot be doing if it has to charge through the day to keep going.
On a standard daytime tariff at 13p / kWh if I always charged at home I'd get about 3.5p/mile with no heater use. With heater use in the winter that will rise to around 4-5p/mile. So 2p/mile using daytime electricity just isn't going to happen, unless I made a lot of use of free public charging to cut my overall cost.
They specifically mention that they did a lot of rapid charging on the car (eg 30 minutes to 80%) and it makes sense that they would have to do that as a taxi to keep it in operation through the day, however in England you pay quite a bit for most Rapid chargers - WAY more than 13p/kWh let alone 7p/kWh. So unless the taxi company owned and ran their own rapid charger (possible, but quite unlikely) I can't see any way they could possibly be achieving 2p/mile, even in the summer, and unless their Leaf has a heat pump the cost to run it would go up by about another 50% in the winter.
One other point is that rapid charging is not nearly as efficient as normal slower charging - it generates quite a bit of heat that has to be taken away through active cooling, so even if the electricity tariff at the rapid charger was the same as at a normal 3 pin plug it would cost you a bit more due to the inefficiency of charging a battery so quickly. (I don't know what the figure actually is, but I'd estimate about 20% loss of efficiency charging a battery in 30 minutes vs 6 hours) It sounds like a lot of their charging would have been done as rapid charging, since they're trying to run the car as a taxi.
So I don't think too much in the way of fact checking was done in the article on that 2p/mile claim!