The high voltage battery is the most expensive component of an EV. What maintenance steps are required to maximize service life? While we previously discussed that most batteries are designed to outlast the vehicle with normal use, now lets look at official manufacturer documentation to see their recommendations for maximum battery longevity.
The five popular brands we studied took slightly different angles on battery care. We can learn a lot by aggregating all of their advice, because it generally applies to all EV lithium batteries.
Spoiler: The one common thread between all manufacturers is to minimize the amount of time a battery is kept at an extremely low/high state of charge.
In the manual for the Model Y, Tesla’s main advice is to avoid discharging the high voltage battery to zero (and strong emphasis to prevent the vehicle from sitting at zero percent charge for an extended period of time).
- Never allow the Battery to fully discharge. Even when Model Y is not being driven, its Battery discharges very slowly to power the onboard electronics. The Battery can discharge at a rate of approximately 1% per day…
- The most important way to preserve the high voltage Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it.
So the official advice is to minimize the time the vehicle spends at zero percent, if you’ve drained the battery that low. Keep in mind that the car will consume ~1%/day even when not in use, so before parking your vehicle for an extended time, either top it up, or leave it plugged in, if possible.
In the manual for the Mach E, (page 149) Ford says that it is acceptable to use the entire battery in everyday use. However, adhering to the following three best practices will improve longevity of the pack.
- If your vehicle reaches a 0% state of charge, recharge your vehicle as soon as possible.
- Allowing your battery to cool before charging and setting the maximum state of charge to 90% for everyday usage improves longevity of your high voltage battery.
- When you park your vehicle for an extended period of 30 days or more, we recommend your battery be at an approximately 50% state of charge. Storing your vehicle’s high voltage battery at higher states of charge is less favorable than storing at lower states of charge.
In summary; batteries do not like to be at zero or 100 percent for too long. A 50% state of charge is optimal for longer term storage. Setting a daily charge limit of 90% is a good balance of available range and avoids battery storage at too high of a state of charge.
The same theme continues with Volkswagen. In the Quick Start guide for the ID.4, Volkswagen outlines three rules for getting the most out of the battery pack.
- For daily usage, Volkswagen recommends setting the charging target at 80%. Before long trips, Volkswagen recommends setting the charging target at 100% for the highest possible range, and then driving off as soon as possible after charging is completed.
- If the vehicle will be unused for longer than 12 hours, leave it parked with a battery charge level of at least 30% and no more than 80%
- When possible, avoid regular fast charging with direct current (DC).
The owner is free to use the entire battery as they please. But most of the time, a private car is parked and not being driven and it is effectively in storage. The advice aims to minimize the amount of time a battery spends at too high or too low of a charge. In addition, Volkswagen discourages the use of Level 3 DC fast charging as a main method of charging due to increased heat wear on the battery pack.
Polestar’s guidance is perhaps the easiest for most people to understand. It is communicated in four short bullet points in the Polestar 2 manual:
- Plug in the charging cable when the vehicle is parked. Especially in very hot or cold weather
- Avoid discharging the battery completely to 0%
- If the charge level is 0%, the battery should be recharged as soon as possible.
- Avoid fully charging the battery to the maximum level unless needed for the distance you will drive.
It includes all the familiar advice, but the first point on hot and cold weather is an interesting observation. Polestar’s native country of Sweden can certainly have extreme temperatures in the winter.
Batteries do not like to be too cold or too hot for long periods of time. Spending time below freezing or in extreme heat may cause earlier degradation in capacity. Most modern EVs are able to warm or cool their high voltage batteries to maintain a desirable temperature for storage. For this reason, Polestar recommends keeping the car plugged in while parked, because active heating and cooling consumes energy.
The manual for the Ioniq 5 repeats mostly the same guidance and warnings as the rest of the EV manufacturers.
- The battery capacity of the high voltage battery may decrease when the vehicle is stored in high/low temperatures.
- If the vehicle is kept with insufficient charge for a long period, it may damage the high voltage battery and the high voltage battery may have to be replaced depending on the level of degradation.
However, one unique directive from Hyundai is regarding their V2L (vehicle to load) function. V2L allows drivers to plug-in external high power loads to the car to utilize the high voltage battery. (Think powering an appliance, or recharging an e-bike)
- Using the V2L function may reduce the mileage due to the use of high voltage battery energy, and repeated use of the V2L function may cause a decrease in the life of the high voltage battery.
Hyundai warns that utilizing V2L excessively may wear out the battery faster because you would be adding more load cycles (charges and discharges) to the pack in addition to the wear from driving the car.