Eight Tips to Extend Battery Life of Your Electric Car
People considering a plug-in vehicle have a legitimate concern about how long EV batteries will last before they need to be replaced. The answer depends on how you use (or abuse) your vehicle’s batteries. With proper management—and following the tips in this article—the batteries in a modern EV could last decades, allowing plenty of time for the technology to go mainstream and for economies of scale to bring down the price. (Keep in mind: Nissan and General Motors and other carmakers currently provide EV battery warranties for eight years and 100,000 miles.)
Check out these tips—but of course, if your owner’s manual contradicts anything you read here, follow the instructions from the manufacturer.
1Avoid full charging when you can.
One reason that batteries in mobile devices only last a couple years is that they are being pushed to their maximum capacity—frequently getting fully charged and fully drained. Consumer products are advertised by their battery operation time, not their battery lifespan. This means that every possible electron will be shoved in there. Charging to maximum capacity might give you the most possible use for that one charge, but it is one of the worst things that you can do to lithium batteries.
In the 2011 Nissan LEAF, there is a Long Battery Life setting that tells the car to stop charging at 80 percent. This reduces the available range, but could greatly increase the lifespan of your battery pack. If your normal daily driving can be done with less than an 80 percent charge or you can charge mid-day, this simple setting is one of the easiest things that you can do to increase the battery’s lifespan.
One additional advantage of not charging up all the way is that it leaves room to store energy from regenerative braking. Often when the batteries are full or near full, regen will be disabled to avoid overcharging the batteries.
2For pure EVs, avoid deep discharging your battery pack.
Lithium-ion packs prefer a partial cycle rather than a deep discharge. Since lithium-ion chemistries do not have a memory effect, there is no harm using a partial discharge. Not only will this avoid excessive wear, it will also mean that—with a little planning—you will arrive at your destination with range to spare.
The Nissan LEAF has 12 “fuel bars” that tell you the charge level of the batteries. Just like you were taught to keep your hands on the wheel at 10 and 2, it is a good idea to keep your LEAF’s charge level within 10 and 2 bars of charge.
EV drivers are often asked, “How far can you go on a charge?” But if you can help it, avoid trying to personally find out for yourself by driving all the way down to an empty battery to test your electric car’s full range.
3For plug-in hybrids, consider “mountain-mode” or leaving EV-mode at key times.
In a plug-in hybrid like the Prius Plug-in Hybrid, or a range-extended electric vehicle such as the Chevy Volt, it’s more common to use all of the available battery capacity before switching to gasoline power. Fortunately, the vehicle’s battery management system knows when to stop drawing from the battery—to avoid deep cycling.
But if you know that your planned route includes a long hill climb, switch to Mountain Mode—which kicks on the gas engine and saves juice in the battery—at least 20 minutes before you start the climb. This will ensure that the batteries are not deep discharged during a long steep climb and you’ll have all the power you need to pass as you go up the mountain.
The Toyota Prius Plug-in Hybrid gives drivers the similar option of voluntarily pushing the car out of EV mode—and for a period of time use more gas and less battery.
4Use timers to minimize the time spent at a high state of charge.
You may have heard that, in many cases, it’s better for the grid, the environment, and your wallet if you charge your EV at night. (See our Top Five Rules for Electric Car Utility Rate Plans.) But careful timing of your charging schedule is also better for your batteries. Again, the idea is that lithium-ion batteries are most stable when they are about half charged—not too full and not too empty. However, a 50 percent charge may not provide adequate range for your daily driving—or may push your state of charge to the limit during your very next commute.
So how do you keep the batteries in their most stable state as long as possible while still ensuring that you have enough range when you leave in the morning? Many electric cars and charging equipment providers offer the ability to program the time of day the charging takes place. The best practice is to set the timer so the vehicle is at the charge level you need about 60 minutes before you plan to leave. Delaying the charge minimizes the time the batteries spend when the cell voltage is high.
The 60-minute buffer has two purposes. First, if something unexpected comes up, like an unscheduled meeting at work, you are not waiting for your car to charge in order to leave. Second, this time allows the batteries time to cool down after charging before they are used for driving. (This second reason is not as important during cold weather, since this warmth would help fight the cold.)
One exception to delaying the charge is if the batteries are almost completely drained. In that case, it’s best to begin charging as soon as possible.
5On a hot day, try to park in the shade. During the winter, park in a garage, rather than on the street.
Many electric cars have thermal management—via air or liquid—that is great for keeping your batteries comfortable, but it comes at a price. Running fans and AC compressors use energy. On a hot day, if you were to park your car on a hot asphalt parking lot, you would not want the thermal management system to run continually. If it did, hours later when you came back, your batteries could be somewhat drained from cooling themselves. Alternatively, the car’s thermal management system could run for a few minutes after parking and then shutdown until the vehicle is restarted. That means that after that cool-down cycle completes, your batteries are slowly being heated by their surrounding. Neither of these solutions are ideal for battery longevity.
6Tip: If your EV has thermal management and the weather is extreme, plug in whenever you can.
This will, of course, charge your batteries, but more importantly, it will engage the thermal management system continuously without draining the batteries. Remember that lithium batteries like the same temperature ranges that you and I do. If you had to sit in the sun in a hot parking lot, would you want the AC turned on? Yes, you would and so would your vehicle’s batteries.
7Plan ahead for period of extended storage.
The Tesla Roadster has a “storage mode.” This makes it easy: plug in the car, set it to storage mode and the vehicle’s firmware takes care of the batteries. If your plug-in vehicle has a special storage mode, use it. If not, and you will not be driving your plug-in car for a month or more, here is what I recommend: (1) Store the vehicle in a cool, but not freezing, location; (2) Charge to 60 percent; (3) The batteries slowly self discharge; (4) When the charge is below 20 percent or 3 months later, whichever comes first, charge the vehicle back up to 60 percent.
With Internet-enabled EVs such as the LEAF and Volt, you can run a smartphone app and check the charge level. When the charge is below 20 percent, you can even initiate charging with these apps.
If you have your car in storage mode for a month or more, this can cause the batteries to become unbalanced. If the pack is unbalanced, your range will be greatly reduced. To alleviate this problem, simply fully charge your batteries before the next time you drive the car. Even if you generally use an 80 percent charge, the next two times you charge the car after a storage event, charge it all the way up. This will ensure the batteries are rebalanced.
8To maximize battery life, minimize use of DC quick charge.
I have saved the best for last. DC quick chargers can dump about 80 miles of range into the Nissan LEAF’s battery pack in 30 minutes. Fast charging is very useful if you need to drive more than the vehicle’s single-charge range in a single day. However, the batteries pay a price for this convenience.
Regular use of fast charging will cost you about 1 percent of capacity per year. For example, if you avoid fast charging, you may have 80 percent capacity after 10 years of normal use. However, if fast charging is your primary fueling method, then your capacity would be 70 percent after 10 years. While the cost to the battery’s lifespan may not be as much as you may think, fast charging still takes a toll that should be avoided when possible.
These tips can extend the life of an electric car’s batteries, but I’d like to make it clear that most are not absolutely necessary. With modern plug-in vehicles, you can simply plug them in anytime and drive it any way that you see fit and you should still have batteries that perform well in 10 years. The manufacturers already build in precautions so you cannot overcharge, over-discharge, or over heat. These are the biggest impacts to lifespan. Still, the tips can help wring a few more cycles out of your pack—and show you how to enjoy your EV while maximizing battery lifespan.
You can choose to be a battery-babier or a battery-abuser. That's up to you. For many of these tips, there is not extensive data that demonstrates exactly how much more life you can get. To quote Sammy Hagar, “Only time will tell if we stand the test of time.”
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