Transportation: EV battery life

Tesla does not say how many times its batteries can be re-charged.  Since the number of charge cycles is dependent on many variable factors, that is understandable for Tesla not to provide a number. They do provide an 8-year, 90% capacity guarantee option, however.

Panasonic, which makes the batteries, citing laboratory tests (which may be very different than real world conditions) says about 6,000 cycles. An EV that drove 200 miles between charges would then see 200 x 6,000 or 1.2 million miles; the vehicle and various components would give out before that, if true.

Let’s assume half that rating or 3,000 cycles – then we’d see 600,000 miles, possibly in line with the maximum real world life of other components, and  way ahead of most vehicles on the road today. Amortizing your vehicle costs over 600,000 miles with minor maintenance (EVs need less maintenance than ICE[1]), tire replacement and so on, would provide a surprisingly low cost per mile. As noted below, this could be a very important factor in applications such as taxis which may drive 200 miles per day, every day. (And note that newer Teslas can get well over 300 miles on a full charge.)

At 200 miles/day, a car would rack up a million miles in just over 13 years. A taxi with a more normal 250,000 mile life (which is how long New York taxis last) is worn out in 4 to 5 years. If you can make the vehicle last that long, you seriously reduce the depreciation part of the robotaxi economics model and thus reduce the cost of a ride, since today depreciation is the largest cost factor in operating a car. Depreciation of the battery has been one of the largest costs of operating (and fast charging) an electric car. In fact, you can reduce depreciation so far that it becomes secondary to other costs like energy, risk, maintenance and logistics.

Source: Tesla’s Battery Guru Describes A New Cell With Massive Lifetime

Related: What causes batteries to lose capacity or fail more quickly?

From that web page leading factors in reducing capacity are:

  1. High temperatures.
  2. Overcharging or high voltage.
  3. Deep discharges or low voltage.
  4. High discharges or charge current.

Not shown, but cold temperatures reduce the operating range which can then, in turn, lead to deep discharging the battery.

There isn’t a one size fits all answer then to how many charge cycles are available in a battery. Some real world users have reported significant degradation at 50,000 miles while others have said they see minor degradation as they have passed through 100,000 or 200,000 miles. The number of cycles varies based on which EV vehicle you have, battery capacity and chemistry, whether the vehicle does effective pack and thermal management, and how the vehicle is used and how the battery is re-charged.

Nissan claims 8+ year battery life for their smaller 30 kwh pack in the Leaf. In fact, their real world data suggests much longer life, resulting in batteries being usable well beyond the life of the vehicle. This had led to suggestions that “old” EV batteries might be repurposed in a second life after the car wears out, such as in solar PV installations.

VW, meanwhile, expects its batteries will have 70% of capacity after about 100,000 miles.

[1] Tesla maintenance, which generally can only be done at a Tesla authorized dealer, is said to average about $500 per year, which is considerably less than ICE vehicles, serviced at dealers (over time). That, however, includes routine items like changing wipe blades, some fluids, light bulbs and what not, which are presumably items that the end user could elect to do themselves, saving money.

EVs, however, do depreciate faster than ICE vehicles, at least for now.

Installing a home charger can cost $1,000 and up, depending on availability of a 220 circuit and/or the need to run a long line and install a subpanel.