The Expert Podcast

So what everybody wants to know about buying an electric vehicle is how much EV range do batteries lose over time. If you purchase a vehicle that has a 200 mile range, is it going to be the same 200 mile range in a year and two years and three years, or will that range diminish? And there's a lot of variables that go into that range reduction, but there's a new study that was done by a company in Canada where they actually did X-rays at the inside of a battery showing what happens to the cells and the physical condition of the battery internally.
This was a very difficult thing to do in the past because in order to discover the internal condition of a battery you have to take it apart and the dismantling of a battery damaged the things that you had to observe to check out the battery. Plus you can only evaluate the battery at one point in time. With X-rays you can keep looking at that battery over time to see how different uses affect the condition. So what they found is their factors that are known for batteries have to do with the deep discharge conditions and also the frequency of discharges.
One of the rule of thumb stats that some vehicle manufacturers and battery manufacturers say that batteries lose 10 percent of range after 200,000 miles, but even that one quote is kind of misleading because mileage on the vehicle traveling over a road doesn't do anything to reduce the battery, doesn't do anything to degrade the battery, unlike an internal combustion engine vehicle that mileage literally wears out the engine. Batteries don't degrade just because of mileage, they degrade because of charge and discharge and also the depth of charge. Some school of thought now says it's maybe three to four percent a year. Sometimes it's talked about in terms of the cycles, how many cycles charge and discharge. One of the common accepted standards for battery is don't ever let it go down to zero. If you let it go to zero, that's what does damage to a battery. The X-ray analysis of the batteries prove that out.
One driver reported that their new Tesla that they had originally had 250-300 miles worth of range after a full charge when they bought it new. Now a few years later they barely have a hundred miles of range. In fact, when they see that it shows 150 or 140 miles, sometimes the car will shut off at that point. In cold weather it's even worse. The full performance capability of a car isn't available until sometimes it's down to 100 miles. Sometimes you can't even get full power and full speed out of a car in cold weather.
One of the things that some drivers have found is full charging or fast charging can be a factor. When you fast charge it seems like it does more degradation of the battery. Again the X-rays have proven that point. Part of the problem too is some vehicles come with a free subscription to fast charging at certain networks. There's Electrify America which is EA and some vehicle manufacturers will give you a free subscription to that for two or three or four years. The problem is if you routinely use that fast charging, that might damage your battery more than just plugging in at home with a slow charger. Fast charging really is designed to use in limited cases where you have to get it back up to full charge quickly because you're on a long trip. It adds to battery degradation. You probably don't want to use the 480 volt fast charging unless you're on a long trip.
Part of the problem too is that EVs are relatively new so some people have been reported that they've lost 10 or 15 or 20 percent of their range after 100,000 miles. The problem is there's not many people that have EVs with that many miles yet because it's a relatively new technology. Some of these vehicles are only three, four, five years old and you don't have a hundred thousand miles. There's one owner that has a Nissan Leaf that reported with 55,000 miles on their vehicle, Nissan Leaf, that he still has 11 bars or 90% capacity, but that means 80 miles instead of 85. For most people that might be fine, but that vehicle only has 55,000 miles.
Another person says that their battery pack on their Tesla is unusable and they would have to pay twenty thousand to get a new one where even a used one is going to be 15,000 for a used battery. So let's take a look at the X-ray analysis of a battery. This was done by a company called Canadian Light Source that does a lot of X-ray inspection of all kind of industrial parts, aircraft manufacturing for safety reasons, and it was published in what's called the Journal of Electrochemical Society. And it shows how the discharge cycles of battery cause physical damage every single time.
Part of the reason is as electric vehicle batteries have more capacity they're built with more dense parts, meaning that the plates and the dividers are packed closer together. The more energy you pack in, the faster the battery will degrade because charging forces lithium ions between other atoms in the electrodes and that pushes them apart. Adding more charge causes the materials to grow more and then shrink down. It's kind of like potholes in a northern state when you have freeze and thaw. The ice freezes cracks in the road and then it thaws in the summer and then freezes in winter. Every single one of those freeze and contraction makes the cracks get bigger and you see it if you live in any northeastern or northern climate, you see the cracks get bigger every year.
This is happening on a microscopic level inside electric vehicle batteries. When they shrink back down and grow, those cracks form and then it slowly reduces the ability for that battery to charge up more because the cracks degrade the charging process. Eventually the materials inside can crumble according to the engineering source and parts of the battery can even peel apart from one another and that can cause large scale damage. In extreme cases it can cause fires, but even in normal cases it can degrade the range of the vehicle over time. If you have a 250 mile range, then it's 200, then 150.
So they're looking at using different coatings and different materials in the batteries to make it better, but the most important thing is until more robust batteries for electric vehicles are produced to make sure that you're not doing things to your electric vehicle that would cause the battery to degrade more than it has to. Things like fast charging unless it's necessary, things like letting the battery go to zero. If you let that battery go down to zero, that's going to have a very significant effect on the battery. Make sure that you're not charging from zero in very cold weather because that's going to change the chemistry of that charging process. Draining the battery a small amount causes less damage than draining it all the way. It's kind of like you know if you're moving a piece of material a little bit it's not going to bend it that much. Charging a lot causes more physical changes to the chemistry of the battery.
It's important to understand that other uses of that battery are occurring even when you're not driving. The battery has probably a built-in internal heater to keep it from getting too cold. There's other parasitic drains on your battery even when the car is not being driven. Keeping the computer running, keeping the camera running, or theft prevention devices running, all those are going to drain the battery a little bit. So you also want to make sure that you're trickle charging it enough to keep that offset. You don't want to let it get down too low or you have to fast charge it or charge it from zero. Your computer in your vehicle will determine how much charge it needs so you can leave it plugged in in most types of electric vehicles.
So the big takeaway is this: if you have an electric vehicle there are things you can do to extend the life of the battery and it's basically the same things you do on an internal combustion engine. Don't be harsh, don't slam on the gas, don't slam on the brakes, don't run the battery down low, don't charge it up fast. If you're gonna go on a long trip you may have to do fast charging occasionally, but use the fast charging availability for times when it's needed, not just a normal everyday practice.
And if possible do regular testing on your battery. See if your infotainment system has feedback or analysis that you can look at that will tell you what's going on with your battery. Keep a log of what your full range looks like, maybe at different temperatures, maybe as the car ages. You can say okay my full range says 252, now it's 241, now it's 238. You can get a sense for how fast the battery is degrading and there might be updates that are over the air updates that your vehicle will have that can enhance some of that battery usage or modify how it's charging and discharging.
The internal analysis of the battery is not something you can do physically by looking at it like in this case with an X-ray, but your diagnostic system in your vehicle or even maybe a diagnostic system at the dealership can give you an indication of how you're doing. Keeping your vehicle battery in the electric vehicle lasting longer than average in maintaining that investment because that's the most expensive part of the vehicle is the battery. Five figure is easy: 10, 15, 20,000. So you want to protect it just like you protect any other valuable asset.