Buying a used EV raises questions about the condition of the battery; a new startup is addressing this need with big data.
Read MoreEV performance records document real-world battery degradation rates
They found an average of 2.3%/year range loss for the EVs on the road today. “If the observed degradation rates are maintained, the vast majority of batteries will outlast the usable life of the vehicle.”
Read MoreReminder to EV owners in the LPEA service area (La Plata and Archuleta Counties, Colorado)
On 1 July LPEA initiated a “demand charge” for residential electricity users. The point of the new charge is to “bend the curve” of electrical demand down at the time of day when high use is straining the capacity of the grid. EV owners are exceptionally well placed to assist in this endeavor, because most can automatically shift their charging time away from the peak demand period (4-9 PM) until later at night, when surplus electricity is available. Regardless of the new charge on our electric bills, this is a great idea, as shifting EV charging to times of power surplus will reduce the need to build more power plants. In most cases, this will not inconvenience EV users in the slightest; on the rare occasions when it might (you need to drive again in the evening after arriving home with a dead battery), tap the “override” button on your car’s charging display when you plug it in, and it will charge immediately.
The charge works as follows: LPEA calculates which single hour of a billing month you used the most electricity between 4 and 9 PM. It then charges you a high rate ($1.50/kwh) for that hour. Note that LPEA’s power supplier (LPEA has an electricity bill to pay too, for purchasing bulk electricity from Tri-State) charges 460 times more for the one hour of highest usage per month than it does for power used at other times. LPEA is passing a tiny fraction of this surcharge along to the consumer in an effort to nudge residential customers into shifting their usage to other times of day (https:\\lpea.coop/rates#collapse-accordion-173-4). Note that this extra charge does not apply to residential users that have already adopted time-of-use billing. Most EV users that do not have their own generation (e.g., photovoltaic [PV] panels) are likely to benefit from time-of-use billing. Most residents with PV panels with not benefit from time-of-use billing.
To automate your car’s charging schedule, open the charging options screen on your car’s dash and set the hours of 4-9 PM to be a “peak electricity” billing time, set the charging schedule to prioritize charging during off-peak hours, and then set the other options to ensure that your car will be charged by the time you are likely to next need it (typically 7 or 8 AM). All EVs have some menu choice to easily override this charging block-out, on specific occasions when overriding is desired. For example, on my Volt, a window pops up when I open the charging port, and the button across the bottom of the screen allows me to “override this time.” EV owners’ ability to shift electrical use to non-peak hours is one of the primary reasons why electric utilities love EVs.
Battery Best Practices
When I got my first EV (2017 Nissan Leaf), I gathered from various sources there were things you should do and things you should avoid to extend your car’s battery life. Batteries make up about 35% of the cost of an EV, so you want to make them last. However, the owner’s manual was light on advice and the internet was full of conflicting information about what was important.
By Tennen-Gas – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8249799
An EV-savvy friend told me the simplest rule was to keep your battery between 10% and 90%, and don’t let it sit at 100% charge for long time periods. When you fill it to the top, start drawing it down soon. That is good advice, but I like to know WHY a thing is important and WHO says so.
Finally, University of Michigan researchers have studied the issue and came up with some easy to understand best practices. Why should we care about treating our EV batteries right?
Battery degradation causes premature replacement or product retirement, resulting in environmental burdens from producing and processing new battery materials, as well as early end-of-life burdens.
Center for Sustainable Systems, School for Environment and Sustainability, University of Michigan researchers
Below are eight best practices as summarized by the Electrek.co article cited in the quote below. Follow the link to the article to learn more about the study.
Here are the 8 recommendations that we summarized from the paper. We note which brand of vehicle provided the guidance in its owner’s manual.
Journal of Energy Storage studies EV owner’s manuals, compiles best practices for batteries
- Every manufacturer includes a warning about high temperatures, though different strategies are suggested. Most companies do not cite a specific high temperature in which to avoid vehicle operation. Those that mention a specific temperature use either 50° C / 122° F [Fiat-Chrysler] or 60 °C / 140° F [Tesla].
- Plug in the car anytime it is hot, thereby allowing the battery cooling system to run as needed [Tesla and GM].
- Avoid parking in the sun on hot days [Kia]. When the vehicle is plugged in, the BMS (battery management system) will measure the temperature and take the appropriate warming or cooling action before charging begins [Tesla, Ford, GM, Nissan, Honda], and may disable fast charging capabilities [Kia]. The researchers advise: When the vehicle is running or charging, the BMS will regulate the temperature of the batteries, so it is most important to be aware of high battery temperatures when the vehicle is parked while not charging.
- Dealing with low temperatures is also cited by almost all EV owner’s manuals. Plugging in the vehicle when it is cold (below 0° C / 32° F) is recommended so that the battery heating system can run on grid power. The battery warmer will automatically activate below a specific temperature unless the battery is both not plugged in and under 15% charge (to avoid over-discharge) [Nissan].
- Extremely low temperatures for extended periods may cause irreversible damage, necessitating battery replacement [Mercedes-Benz]. The lower temperature limit for batteries is cited as −25° C / -13° F [Nissan, Mercedes-Benz] or −30° C / -22° F [Tesla, Honda].
- Over-discharging will typically not occur during operation. The BMS will turn off the car and cease operation before severe degradation occurs. However, if the “empty” battery is then left for an extended time without being recharged, the battery can enter an over-discharge state due to the slow self-discharge that occurs even when the battery is not operating. Some manufacturers are concrete, instructing owners not to leave the vehicle parked for more than 2 weeks with a low battery (20% state of charge) [Tesla, Mercedes-Benz].
- If possible, don’t allow the battery to be run all the way down, or left idle for extended periods [BMW, Hyundai, Kia, and Honda].
- The majority of manufacturers do not include information in their manuals explaining that fast charging can lead to accelerated battery degradation. Those that say use of fast chargers should be minimized to maintain battery life [Ford, Nissan, Kia, Honda].