The battery pack is the most valuable single component of an EV, and as such it’s not surprising that you might want to know how to best extend its life.
Fortunately there’s a lot of things you can do! So let’s have a look at some of the top ways you can ensure your EV’s range stays as high as possible.
Try and commonly charge in the 20% to 80% range
In general, this tip applies not just to your EV, but to all devices that use lithium ion battery technology. Things like your laptop, iPad, smartwatch, smartphone and even drone all use lithium ion batteries. By making sure to only charge them to a maximum of 80% during daily use it can dramatically increase their shelf life.
Many scientific studies have been done to compare the Depth of Discharge (DoD) and the number of cycles this relates to. Advice taken directly from Battery University states:
A partial discharge reduces stress and prolongs battery life, so does a partial charge.
As such it’s highly recommended to try and keep your EV in between the 20% and 80% points as often as is possible. This way you’re only giving the car a ~60% charge at any given time. In their tests they demonstrate that a battery that is always charged between 20%-80% (ie 60% DoD) lasts up to 2.5 times longer than the same battery charged from 0%-100% (ie 100% DoD) all the time.
Do note that these tests where on “1500 mAh pouch packs” that are commonly used in mobile phones but EV batteries do behave very similarly. In fact the smaller amount of discharging and charging you do, the better. If you can keep the battery between 40% and 60% all the time it should last even longer. One Tesla battery expert recommends a 70% charge threshold as working well too.
Of course, if you need 90 or 100% of your EV’s battery for a specific trip then go for it and fully charge – but if you want to keep your battery in great condition, then charging to a lower threshold is the way to go.
While it’s often a huge pain to charge a laptop only to 80% – as you have to literally watch it and unplug it at the 80% mark – many EV’s thankfully have a self monitoring system that you can configure.
As you can see in the image above, it’s very simple to go into the Tesla app and pick exactly when you want your car to stop charging by just sliding the little white bar left or right. By default Tesla sets this at 80% but if you’re heading out for an interstate trip the next day you can easily push it all the way to 100% to get the maximum range.
Doing this once in a while isn’t anything to be concerned about but the more you can keep it between 20% to 80% day to day, the better.
Look out for EV’s with active thermal management systems
Just like full charges or discharges of a battery can negatively affect battery life, so too can extreme temperatures.
A battery dwelling above 30°C (86°F) is considered elevated temperature. Exposing the battery to high temperatures in a full state-of-charge for an extended time can be more stressful than cycling. – Battery University
As such, you want to try and keep the battery at its optimal temperature all the time which is what thermal management systems do. Not all BEV’s use the same type of thermal management systems for their batteries though. Some use active ones while others simply use passive ones.
The active units have fans and AC that actively manage the batteries temperature. Think of it like your house and how you like it nice and warm in the winter and nice and cool in the summer. You turn the AC on and it helps to maintain the temperature. This is what an active thermal management system does for your EV’s battery.
All Teslas have active thermal management systems in them and this is why they recommend plugging your Tesla in overnight. That way the car can draw power to keep the battery at the perfect temperature all night long and not drain the battery.
The passive thermal management systems are cheaper and generally just have the battery sitting there in whatever temperature it is. Of course car companies try and insulate the batteries, but this can only do so much and there’s no way to increase or decrease the batteries temperature if it gets too hot or cold.
This leads to the battery being exposed to hotter and colder temperatures than is optimal and so it degrades quicker over time. Both the old and the new Nissan LEAF’s use passive thermal management systems and as such, have not faired as well over the long haul.
Now while you can’t buy a Nissan LEAF and then do anything to make it use an active thermal management system, you can chose not to buy a BEV that has a passive system in the first place.
This will side step all the long term issues you might see from extra battery degradation and all it takes is knowing what to look out for while you’re purchasing the car to begin with.
The slower the charger, the better for the battery
While things like the Tesla Superchargers are fantastic and enable true long distance trips for EV’s, they do have a slight downside. This is that because they are charging the batteries at a much higher voltage level, with repeated use they slightly reduce the long term life of the batteries.
The lithium ion technology prefers being charged more slowly at a lower voltage as this extends the overall life of the battery. That being said, the vast majority of EV owners won’t use Superchargers or other DC fast charging systems enough to encounter this issue.
Tesla even has specific limits built into their battery management systems to slow down the Supercharger charging rates once the car has been charged at Superchargers too many times. As demonstrated in this piece, you have to use literally hundreds of DC fast chargers and Superchargers in order for it to slightly throttle the charging voltages. According to Tesla less than 1% of their customers ever act in this way.
Most of the time, most EV owners will charge at home on relatively slow AC Level 2 chargers and this is the best way to do it. The lower voltages put less stress on the batteries and prolong the life of them. It is also more convenient too.
Common battery warranties from EV manufacturers
While not specifically a tip on how to extend your EV’s battery life, it’s good to know that major car manufacturers offer excellent battery warranties as it helps to put your mind at ease.
Below are a few examples for the most common EV’s here in Australia:
- Nissan LEAF: The battery pack is currently guaranteed against capacity loss for 5 years or 96,500 kms and 8 years or 240,000 kms against defects.
- Tesla Model S or X: Your Model S or Model X is protected by an 8 year or 160,000 km (whichever comes first) New Vehicle Limited Warranty and 8 year or unlimited miles Battery and Drive Unit Limited Warranty.
- BMW i3: The battery is covered by a warranty of 8 years or 100,000 km.
As you can see, most battery warranties will cover you for quite a while! None of them say what they expect the batteries capacity to be at after 5 or 8 years but early tests done on hundreds of Tesla users point to quite positive results.
In a video presented by Teslanomics they show that when you look at hundreds of Tesla owners that have all driven a huge range of miles over the years, a common trend emerges. The capacity of the battery goes down a few percent after the first year but then it stabilises around 91% even after driving over 350,000 km’s!
That means that even if you drive a decent amount, say 17,500 km’s a year, you should still have 91% capacity after 20 years of use. Of course, no one’s had their Tesla for 20 years yet as the company isn’t even that old but it’s an excellent trend we’re seeing.
So how has your EV battery held up over the years? Let us know in the comments in the Drive Zero Community.