Now that I’ve been driving the C-Max Energi around for a while and have established, more or less, a routine with it I’m figuring that I’ll notice more degradation in the C-Max’s battery over the course of the lease than I did with the FFE.
The batteries degrade with usage: The more charge cycles you have and the more deeper charge cycles the quicker a battery will lose some capacity.
For the FFE with its 23kWh battery I would pretty much only charge it up to full overnight and rarely use more than about 50%-60% of the battery. Even on those days where I had to run some errands with it I’d still only use at most another 10% of the battery. When I returned it at lease end with 30,000 miles on it there was no noticeable battery loss.
The C-Max Energi, on the other hand, only has a 7.6kWh battery. This means that I’m depleting the battery daily, sometimes more than once. On the weekends I’m finding that I’ll fully charge it 2 or 3 times per day on both Saturday and Sunday. Thus it is getting cycled more than the FFE battery ever was, and I’m using more of the battery for each cycle.
It is also possible that Ford built in larger margins into the system in the C-Max. The FFE would only charge up to about 90%, and only discharge down to about 10% to protect the battery. Now if Ford designed the C-Max with more room at the top and bottom (like up to 85% and down to 15%, for example) then the battery may be somewhat protected against all the extra cycling.
The C-Max Energi does have a way to preventing it from going too deep into the battery: The EV Later mode. Putting it into EV Later attempts to hold the amount of charge currently in the battery (charge sustain mode). This can be used to prevent deep discharging of the battery–indeed I’ve been using it to prevent the car from going into hybrid mode. When the battery gets down to 1 or 0 miles remaining I’ll put it into EV Later. So far so good but I’m only at about 2000 miles on the clock….