Is it OK to leave Tesla in the sun?

Summer Charging: 5 Warm Weather Tips for EVs

I’m Joe and I lead the EVgo Charging Crew. Please email me at support@EVgo.com or get in touch via Twitter and let me know what I can do to make it even easier and more convenient to fast charge your EV with EVgo.

Whew! It’s hot outside — or at least it usually is during the summer months. As temperatures rise, people who own EVs (or are EV-curious) may be wondering: how is owning an EV different than owning an internal combustion engine (ICE) vehicle when it comes to hot temperatures? This winter, we wrote about how cold weather affects charging and battery range. In warm weather, owning an EV is a little different than owning an ICE vehicle, but not by much.

Summer heat affects all cars, including ICE vehicles. When combustion engines get too hot, parts expand and warp, oil cooks and loses effectiveness, and engines can even seize up. Thankfully, engine cooling systems filled with antifreeze do a good job at keeping engines from getting too hot.

Similarly, EVs have cooling systems to keep their batteries from overheating. The thermal management system for the battery is built to both heat and cool the battery to keep it around 60-80 degrees Fahrenheit. This is quite a bit different from an engine cooling system which is primarily meant to only cool to a range around 190-210 degrees Fahrenheit (a combustion engine also produces a LOT more waste heat than a battery!).

An EV battery performs best within a certain temperature range because its power is generated by a chemical reaction that functions best within that range. When it’s hot outside, the thermal management system uses a small amount of power from the battery itself to maintain temperature (and when plugged in, the system pulls a bit of power from the grid to maintain the battery’s temperature).

All that said, here are a few warm weather tips to help you maximize your EV’s range and keep your battery healthy all summer long.

5 Warm Weather Tips for EVs:

1. Park your EV in the shade or in a garage (if you can).

If you don’t have access to a garage or shaded parking at home, whenever you’re out and about and have the option to park inside a parking structure or out in the hot sun, choose the parking structure! This will allow your battery and the cabin to cool down while parked. You’ll use less battery power cooling your car back down when you get back to your car, too.

2. Precondition your EV before getting inside. (If it’s plugged in, keep it plugged in while you precondition).

Preconditioning allows you to pre-heat or pre-cool the car’s cabin before you begin your journey, allowing you to use less of the energy stored in the battery for these functions. Most EVs come with an integrated app that you can use to precondition (by cooling or warming) your EV’s cabin before you get inside, but preconditioning may also be activated via the car’s media system. It’s best to precondition your EV while it’s still plugged in so that you use energy from the grid to cool the car and your battery down. This gives you more range, along with a comfier car when you get inside.

3. Ease up on the accelerator and brakes.

When it’s hot outside, easing up on the accelerator and brakes will use less energy, which will keep your battery cooler. You can also use ECO mode (or Chill Mode if you’re a Tesla driver), which limits the energy expended when driving.

4. Take it easy on the A/C if you need the range.

By itself, driving in hot weather will have a minimal impact on your range. Using your A/C on a hot day will have a small impact on your range. In fact, the heater in an EV typically uses more energy than the A/C, opposite that of a gas car. In city driving, you can consider rolling your windows down instead of using the A/C, but on the highway, rolling your windows down usually has a more negative effect (by producing drag) than just using the A/C moderately.

**5. Limit your fast charge to an 80% State of Charge (SoC)* and charge at night whenever possible.**

As your charging speed slows down throughout your fast charge, it’s usually a better use of your time to unplug after you reach 80% SoC. The energy transfer from the charger to your battery warms up your battery, so if it’s an especially hot day (and your battery is already warm), your EV may limit charging speeds to keep the battery cooler and healthier. At 80% SoC, you’re probably better off switching to an L2 charger if you need to top off. Charging at night when it’s cooler out will be even better for your battery, and you’ll be conserving energy on the grid if your utility company experiences demand constraints during the day.

If you have overnight charging available for your EV, it’s good to leave it plugged in with the SoC limit set to roughly 50%. For some vehicles, it’s also a good idea to have a small trickle charger, also known as a battery tender, on the 12V battery.*

*Refer to your owner’s manual for more specifics on best practices for your EV model.

As EV adoption grows, many new EV owners might notice that charging and maintaining your EV is similar to charging and maintaining your smartphone. If you’re using your phone on a hot day and have a lot of apps running, it’s often a good idea to close a few apps to let your phone cool down. Your EV is similar. Thankfully, your EV’s BMS and thermal management system do an excellent job keeping your battery cool and healthy.

If you’re curious about what happens to public fast chargers in particularly hot weather, we have good news for you! EVgo chargers are built to withstand extreme weather and shouldn’t experience heat-related issues. If you ever encounter any issues on the EVgo network, don’t hesitate to give our EVgo Charging Crew a call at 877-494-3833.

When the next heat wave comes, we hope these tips help you and your EV brave the higher temperatures. If you’re curious to learn more, check out our Charging Basics page, and click here to find an EVgo fast charger!

Minimise Tesla Vampire battery drain

Your Tesla loses range when parked caused by something called «Vampire battery drain» or just «Vampire drain». This can vary from a few miles per day to quite significant amounts depending on the settings in the car and can be a problem if leaving your car while on holiday. This guide tells you how you can minimise Tesla vampire drain.

What is «Vampire Battery Drain»?

Your Tesla never completely goes to sleep. It contains lots of computer systems that do various functions from monitoring the health of the battery, listening to see if Tesla are trying to connect to the car over the air, being ready to open the doors when you walk up to the car or running Sentry Mode to record anybody approaching your car. The number of computer systems that are running when the car is parked depends on what you ask the car to do while away, and there is a trade off between the number of things being done and the amount of power consumed by the car.

Is it really an issue?

Most of the time the loss is relativity small over a short period of time and as many people plug in to charge over night they do not see the impact of vampire drain. Over the course of a year it can however add up and be quite a considerable amount of energy, Sentry Mode alone can consume over 500kwh per year, which can cost $200/£200 or more depending how much you pay for electricity.

The other situation where it is most noticeable is when leaving the car for more than a couple of days and not on charge. A typical example might be at an airport long stay car park when going off on a 2 week vacation or business trip. The wrong settings could mean the car loses over 2%-3% per day, and a 14 day trip can mean 50% battery loss.

The news is not all bad, with the right settings and use of the car, the loss can be well under 0.5% per day and as low as 0.1%. A recent 16 day trip we had resulted in a drop of 6 miles on our Model Y.

While the HV battery will go into protection mode and certain systems and functions will automatically turn off with a low state of charge, the HV battery also supplies power to the low voltage battery. If this also becomes depleted then even opening the car will be a problem. Access to the low voltage battery is possible but not trivial, and while this battery can be boosted allowing the car to start charging the car will typically still need recovering to a suitable charger.

Using third party Apps

Tesla talk to the car via an API and many 3rd party developers have reverse engineered this and use it for alternative purposes. While the API has improved over the years, and well written applications will not wake up the car when not needed. Some apps are less well written, some even suggest sleep settings, we think these should be avoided as the API now has a specific wake command which should only be used if the car is asleep. As a result settings should not be required.

There are also some services that use the API to control charging. These are typically linked to either solar power at the home, or low cost electricity tarrifs. These query the car to see the state of charge at times when charging would be available at a cheap rate. To get this information they must wake the car to find the state of charge. Unfortunately, these apps do this even when the car is not plugged in, as a result they could be constantly waking up the car while you have left it in a car park.

As an aside, we do not recommend any 3rd party app that retains your any of your details or tokens. The Tesla security is not sufficient and the Multi Factor Security and Pin to Drive are generally bypassed if the Tokens are available to a 3rd party.

To minimise vampire drain, review all 3rd party access and if in doubt, change your Tesla password which will invalidate all third party apps and prevent them accessing your car.

Tesla App

The Tesla app also wakes the car. Avoided excessive use of the Tesla App as very time you open it you are starting up computers and increasing the drain on the battery. Owners sometimes like to check in on the car every few hours when on holiday especially if they are worried about the battery drain and this will just accelerate the vampire drain. The widget you find on some makes of phone will not however wake the car.

Sentry Mode

While in theory a great option, this is a simply dreadful option with respect to vampire drain. The car is kept in a high state of power consumption and is the single most important thing you should turn off to minimise battery drain when leaving the car for any length of time.

Summon

For owners of cars with EAP and FSD, there is a feature called summon available to you. This can have a standby mode enabled which will keep the car awake. This needs to be turned off.

Power Management option

Within some older cars, usually Model S and Model X, there is a power management option for energy saving and «Always connected». The most efficient combination is Energy Saving = On and Always connected left unticked.

In day to day use, many leave Energy Saving off as this is still reasonably efficient.

Climate control

Simply NEVER use Smart preconditioning if your car has it. It rarely works well and can result in the car heating itself up even when you have no intention of using it.

Dog mode, Camping mode etc all use energy from the battery, and while fine for short periods, they should be left off when leaving the car for any length of time.

You may have Cabin Overheat protection and we’d recommend turing this off too. It actually disengaged automatically after 12 hours but the car may still have consumed a lot of energy in that time.

Finally, turn off Scheduled Departure. This preconditions the car on a daily basis which consumes energy.

Software updates

It has been known for the car to end up in a perculiar state following a software update which prevents the car from sleeping. If you notice the car not sleeping or having excessive drain after a software update, manually reboot the computer by holding down the scroll wheels.

Cars may also not sleep when they are downloading an update or new navigation maps. It is best to have the car connected to reasonably fast internet connection if possible as this reduces the time to download the update.

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