How to Maximize your Tesla's Battery Efficiency and Life

Whether it’s the unparalleled acceleration, the eco-friendly footprint, or the futuristic self-driving capabilities, as a Tesla owner you benefit from owning one of the most technically advanced forward-thinking electric vehicles on the market today. Out of all these benefits, one of the most impressive Tesla-related perks is the cost savings owners receive from ditching gasoline. As you may know, your Tesla can absolutely save you money by kicking that gasoline spending to the curb, so much so that Tesla owners can save somewhere in the ballpark of $3,000 over a five year period by charging their EV over filling up their gas guzzler at the pump.

If the goal is to be able to maximize your Tesla Model S, you will first need to understand its inner workings. Since your Tesla’s Li-Ion battery is one of the primary drivers in saving you so much money, isn't it worth understanding how to get the most out of it? Could you use a few tips and tricks to get some more cycles out of the lifetime of your battery? Are you looking for some detailed insight into battery charging practices, rather than following the mantra “Always Be Charging?” Well to address this, we’ve put together the comprehensive guide to maximizing your battery efficiency and extending your battery life.

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Quick battery overview

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To fully address the concept of battery lifetime and efficiency, we should be clear about what we are addressing. What we’re really addressing here is the capacity loss (or degradation of charging ability) of your Tesla's battery over its lifetime.  Furthermore, to effectively discuss capacity loss, we should start with how your Tesla battery even works in the first place! So let’s talk battery basics. If you’re up-to-date on your battery electrochemistry, feel free to skip right ahead as we dig in.

Battery basics & capacity loss

A lithium-ion battery consists of a cathode, an anode, an electrolyte solution and a wire connecting the anode and cathode. The cathode (the positive terminal) and the anode (the negative terminal) of a battery are connected via the wire. The intention of a battery is simply to produce a buildup of electrons (charging your battery) at one terminal of the battery and then allow this discharge of electrons to pass from high potential to low potential when you engage the electrical circuit. This passing of electrons through the wire is how we power all of our battery-powered electronics today.

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Unfortunately, every time you charge the Li-ion battery in your Tesla, you lose a bit of charging capacity or your battery begins to “fade” due to the ion flow in this exchange of energy. Due to some electro-chemistry properties of battery charging, creating that potential between the anode and the cathode and discharging the potential erodes the electrolyte differences that separates the anode and the cathode. This byproduct of battery charging makes it so less and less electrolyte solution is available and, thus, the capacity of your battery diminishes over time.

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Avoiding charging practices that speed up this degradation process are going to be critical to maintain the effectiveness and extend the life of your Tesla battery. Let’s start our analysis by uncovering some different factors that play a role in battery degradation.

In this comprehensive overview, we are going to address the following topics and investigate their influence on battery efficiency and longevity:

1. Tesla Charging Options

2. State of Charge

3. Preconditioning, Smart-preconditioning and Extreme Weather

4. Battery Temperature and Further Weather Considerations

Tesla Charging Options

Overview of charger levels

First a little review. As a Tesla owner, you’ve probably become very familiar with the different options available to you for charging your Tesla. Broken into three “levels”, levels one, two and three; your Tesla can be charged via a 120V supply (level 1) , a 240V supply (level 2) or a 480V  direct current supply (level 3). As a quick reminder here’s a breakdown of charging capabilities for each level:

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If you’re interested in a detailed comparison of home charging stations check out this article on Building an At-Home Charging Station.

For the intention of this section of the article, rather than charger specifics, we are going to investigate how the different chargers influence the longevity of a given battery. After all, in order to learn how to maximize your Tesla Model S, you must be able to maximize its charging capacity.

It's been a long standing conjecture that lower voltage chargers (level 1 / level 2) will have negligible effects on battery longevity whereas the constant use of level 3 DC super charging will speed up the degradation process of your Tesla battery. The long-standing claim here is that heavy use of supercharging will result in a lower charge range, lower lifetime charging cycles and require a battery swap sooner than later. We’ve found there is merit to this claim.

Researchers from the Technical University of Munich support this claim through their research that supports a correlation between voltage, State of Charge (or SoC defined as the ratio between saved energy in the battery and the total capacity of the battery) and temperature.

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As seen in the study above, relative capacity declines with increased voltage, temperature and SoC. Of course, there are three confounding factors here that are shown to negatively impact relative capacity of the battery. Let's look at some other empirical data that addresses applied voltage and its influence on battery degradation.

The Tesla rental service Tesloop analyzed the impact of different charging methods on their fleet of Teslas and found some very interesting results. Based on the findings, they concluded that heavy use (charging multiple times per week) did not accelerate EV battery degradation, whereas temperature and direct current charging played the biggest role in their observed degradation of capacity seen in their fleet. To extrapolate on this finding related to our inquiry, Tesla Charger levels 1 and levels 2, used multiple times per week did not accelerate battery degradation. However, direct current (or level 3 charging) did accelerate battery degradation.

To further support this claim, AVID Technology, a designer of electric powertrain systems weighed in on the battery degradation debate stating “Degradation mechanisms happen more readily at elevated temperatures, rapid charging, and hard driving will result in raised pack temperatures due to the high current flows.”

What seems to be the culprit in battery degradation boils down to the use of direct charging, the frequency of direct charging and additional stressors on the battery like excessive heat strain. What makes this a challenging topic to contend with, is how there seems to be empirical data that supports both stances.

To pull all of the referenced research, conjecture and empirical evidence together, we’ve tried to reduce our findings to some simple takeaways.

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Tesla Charger Takeaways

As we can see through the provided research, charging method considerations really break down into level 1 / level 2 charging versus level 3 direct charging or supercharging.

• Jeff Dahn, Elon Musk and Tesla users state that frequent supercharging poses very little impact on battery capacity degradation.
• Note that Tesla has released an official statement confirming that frequent supercharging possesses the possibility that li-ion cells will slightly decline after a very large number of high-rate charging sessions.
• Research has shown that Tesla owners have permanently damaged their Tesla batteries due to frequent supercharging. Although keep in mind, some user data actually points to daily supercharging actually prolonging battery life.

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Tesla Charger Actionable Steps

• If you are looking for conservative measures to follow, general li-ion battery research suggests limiting direct charging as much as possible.
• Charging level 1 and level 2 seems to pose negligible differences in long term degradation of the battery.

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State of Charge

A hotly debated topic when it comes to Tesla battery longevity is the State of Charge, which is your battery’s level of charge relative to your battery’s capacity.

The reason for considering SoC (as seen in the research provided by TUM above) is that charging practices, such as draining a battery to zero or charging the battery to 100% can accelerate battery capacity loss and even damage a battery beyond recovery. Understandably there is a lot of considerations around best practices here.

Some owners and enthusiasts believe that maintaining around 30% to 70% SoC seems to minimize battery degradation, whereas Elon Musk himself stated that 5% to 90% SoC or lower wouldn’t pose an issue!11 Let's dig in a bit deeper to see if we can’t uncover the impacts of high SoC and low SoC to find some boundaries that promote battery longevity.

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Impacts of a high state of charge

Research referenced by Battery University confirms that degradation of capacity is accelerated at a 100% SoC whereas 40% SoC does not seem to degrade the battery at the same rate.

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As seen in the stated research, 100% SoC provides less recoverability of capacity. Further, it is also shown that capacity loss is accelerated when the battery is under increased heat. Higher temperatures induce higher stress on the battery and thus result in even further battery degradation.

Even though this research shows some pretty large differences in degradation based on SoC, and common sentiment states to charge somewhere between 30% and 70%, Tesla owners seem to not suffer from the same impact on battery degradation through maintaining a SoC above 80%. Further, Tesla's official range tips suggest charging between 20% and 90%.13

On the extreme end, one Tesla user via the Tesla motor club forum stated that he set a daily charge to 90% plugged in at all times while at home, the car is 22 months old and has driven 63,669 miles resulting in a 3.6% battery degradation.

Further, a group of 286 Tesla owners have shared their Tesla battery statistics to track battery capacity loss which has provided some fascinating results. Referenced in figure B below, these owners only sustained around a 5% capacity loss after driving 50,000 miles on their Tesla! Of the research referenced, the common practice was charging to 90% SoC with infrequent supercharging.

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Impacts of a low state of charge

We’ve seen how a high state of charge, especially coupled with other confounding factors accelerates the degradation of a battery. Let’s better understand how low state of charge or Depth of Discharge (DoD) impacts battery longevity.

20% DoD produces the most full cycle equivalents before degrading to 70% of new capacity

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Research referenced by the Battery University shows that depth of charge directly correlates to battery degradation. The research here is estimating the number of discharge cycles before the battery capacity drops to 70%. As we can see this data supports a direct correlation between DoD and the total number of cycles used before capacity dropping to 70%.

Aside from low DoD accelerating battery degradation, leaving your Tesla at 0% charge for extended bouts of time can have a catastrophic impact!

There have been accounts of Tesla owners effectively ‘bricking’ their Tesla battery through some very poor charging practices. By leaving your Tesla unplugged and uncharged for weeks or even months at a time, the main Tesla battery could effectively drop to 0%. This is something you simply do not want to do.

Leaving your Tesla battery at 0% for extended periods of time can cause what's called a parasitic electro-chemical reaction that leaves your battery in an irreversible state where you are no longer able to sustain a charge. Sadly, now it's time to consider a battery swap.

Luckily, even with the smallest amount of thought and effort, any Tesla owner can ensure this does not happen.

If you are not using your Tesla for an extended period of time:

• Ensure that your Tesla is plugged in and double check before long bouts of inactivity! The on-board charging monitor will ensure the battery is kept in a safe SoC state.
• Do not leave your Tesla at 100% SoC for extended periods. This can accelerate battery degradation.
• If you’ve hit 0% charge while driving, don’t worry too much. Tesla has designed the battery maintenance monitoring system to save some charge, even when the battery states 0% to ensure you don’t permanently harm the battery. Just get it charged ASAP.

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Phantom Draining

We should quickly touch on phantom draining as it relates to DoD. Phantom draining is the phenomenon where your Tesla battery loses charge while turned off, inactive and not plugged in to charge. The reason for this slow trickling loss of charge is due to the fact that your Tesla is almost always using the on-board monitoring systems to analyze battery metrics, which consumes power even when your car is off.

Typically this isn’t a problem since most owners leave their Teslas plugged in overnight and phantom draining typically accounts for only a small loss in charge. It’s important to note that Tesla has built in some safeguards so that if you are reaching extremely low levels of charge, some of these computing processes will completely shut off to preserve the health of your battery. As a best practice, ensure that you are setting SoC parameters via your Tesla charging preferences and leave your Tesla plugged in when at all possible. Soc is an imperative element to take into consideration when learning how to maximize your Tesla Model S.

If we can stake a step back and investigate what we can take away from the state of charge considerations.

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SoC Takeaways:

• Long-Standing battery chemistry research supports that a high state of charge will degrade battery capacity and shorten an Li-ion battery’s lifetime.
• Following Telsa’s best practices by not exceeding 90% SoC on a regular basis and only charging to 100% for long one-off trips will still sustain around 5% capacity degradation after 50,000 miles traveled.
• Tesla best practices via the user manual state to charge between 20% and 90%.
• Elon Musk & Jeff Dahn state a more liberal approach of 5-10% - 95-100% SoC posing little negative influence over battery longevity.

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SoC Actionable Steps:

• Limiting high and low SoC to 30% - 70% when at all possible will optimize battery preservation.
• If you regularly maintain an SoC of 90% and infrequent charges at 100%, you should only experience minimal degradation of battery capacity at around 5% after 50,000 miles seen through empirical data.

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Preconditioning, smart-preconditioning, regenerative braking and extreme weather

Preconditioning

The intention of preconditioning is to raise your Tesla battery temperature to a state that is optimal for charging. Imagine exposing your Tesla to extreme cold weather overnight and then looking to charge and drive your Tesla in the early morning. Without precondition, charging your cold Tesla battery (anywhere under 50 degrees F) is going to put a lot of stress on the battery and negatively impact charging efficiency and driving range.

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To preserve the health of the battery, Tesla battery monitoring systems will automatically begin to warm the battery before actually applying a charge to the battery. For Model 3 and Model Y owners, your Tesla will consume power from the charger to run the motor in an inefficient state, and in doing so generate heat to the battery through “Rear Waste Heat Power” and for Tesla 3 this is known as “Waste Heat Mode”. For Model S and Model X owners, your Tesla is equipped with a heat pump that acts as a separate battery heater. Also keep in mind that rear-wheel drive models generate heat only from the rear-motor whereas the all-wheel drive models are going to be able to generate heat from both motors. The difference here is that the rear-wheel drive models are going to generate somewhere around 4Kw power and the all-wheel drive model will output around 7Kw.

What's great is that you can actually observe your battery’s temperature begin to increase in real time while the battery current remains null. There's a video here that gives a visual representation of this phenomenon.

So whether you knew it or not, your Tesla is actually applying the principle of preconditioning when you are charging your Tesla in sub-optimal weather conditions.

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Smart-Preconditioning for the battery

Smart-preconditioning is great for those who live in cold climates and are regularly charging and driving their Tesla in sub-fifty degree weather. The intention of smart preconditioning is to proactively warm your Tesla’s battery based on your driving and charging behavior. Keep in mind there have been some user accounts stating that this feature is ‘buggy’.

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Preconditioning for Supercharging

You can also apply preconditioning when using Supercharging. Tesla recommends preconditioning about 10-20 minutes prior to Supercharging your Tesla. What’s going on here?

Supercharging, or DC charging is going to require your Tesla battery to be at a certain temperature to effectively charge the battery via DC mode. To get the most out of your Supercharging session, preconditioning prior to Supercharging is going to bring your Tesla battery to the optimal temperature and allow for the most efficient Supercharging. There's some great data on the effects of preconditioning here.

If you find that the preconditioning status is still on while you are Supercharging, your battery simply hasn't reached the optimal temperature and requires further heating during the Supercharging session.

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Regenerative Braking

Another consideration pertaining to driving range and battery efficiency is regenerative braking. When you engage the brakes of your car, there's a lot of kinetic energy created in that exchange to slow your vehicle down. Regenerative braking takes advantage of this by treating the engine like a generator and charging your battery while you break. The upside here is that you’re going to extend the range for a given charge and in specific scenarios. This in turn, could provide a net benefit for the longevity of your Tesla battery. One way regenerative braking could help increase the longevity of your Tesla battery is if the regenerative braking helps keep your Tesla from dipping to a suboptimal SoC on consistent long drives. By keeping your Tesla battery in a better SoC range through these mid-ride charging practices, you could benefit from the battery preservation qualities of healthy SoC practices.

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Preconditioning, Smart-preconditioning, regenerative breaking and Extreme Weather Takeaways

• Preconditioning is going to be applied by default in a lot of battery charging scenarios to protect the battery and maximize range.
• Smart-preconditioning is going to warm the battery prior to a drive in cold weather based around driving habits. Keep in mind that this feature has been found to be buggy by some Tesla users.
• Preconditioning for Supercharging is going to bring the battery to an optimal temperature state prior to a supercharger to increase range and promote a healthy charging state.

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Preconditioning, Smart-preconditioning, regenerative breaking and Extreme Weather Actionable Steps:

• Follow Tesla best practices for preconditioning, smart-preconditioning and considerations in extreme weather found here & here.

Battery Temperature and Further Weather Considerations

As we’ve seen in some of the stated research and prior examples, temperature seems to play a role in battery capacity loss. Let’s look at best practices and considerations around battery temperature.

Influence of low Temperature on Battery Longevity

Based on some data provided by Battery University, an Li-ion battery that provides 100 percent capacity at 27 degrees C (80 degrees F) will typically deliver only 50 percent at - 18 degrees C (0 degrees F).

Further optimum performance of a given Li-ion battery is achieved at 20 degree C temperatures (68 degrees F). Given more light to this phenomenon, Munchen Technical University provided some research backing up this claim seen in the following figure.

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This phenomenon isn’t just seen in academic research, a recent study conducted by AAA found that cold weather can temporarily reduce the range by reducing the capacity of a Tesla by 40%!

You may have heard that charging a cold battery can negatively impact or even permanently damage a Li-ion. Even though this statement is true, you shouldn’t worry too much. Tesla’s on-board computer system is constantly monitoring the system state of your Tesla and simply put, your Tesla is going to prevent you from  inadvertently heating the battery too quickly in cold conditions. This is one reason you are seeing decreased range in those colder months, as your relative range per charging session is also being reduced since the battery takes longer to heat and charge efficiency drops in cold weather.

Influence of high Temperature on Battery Longevity

Charging at extreme high temperatures seems to pose similar challenges, although not as pronounced as the effects of charging and discharging Li-ion batteries in cold weather. Some recent research presented by Greatbatch Medical found that Li-ion batteries will sustain an accelerated capacity loss under high SoC coupled with high temperatures.

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Battery Temperature and Capacity Loss Takeaways

• Li-ion battery research supports a temporary drop in relative capacity and decreased range in cold weather.
• Applying a charge to a cold battery can negatively influence long term battery capacity, however Tesla limits this by applying preconditioning when trying to charge a battery in cold weather.
• Li-ion battery research shows that high temperatures coupled with high SoC accelerate capacity loss.

Battery Temperature and Capacity Loss Actionable Steps:

• Except decreased range in colder weather due to inefficiency to battery charging and discharging in cold weather.
• Consider that energy from the battery is consumed to warm the battery and car in inclimate cold weather conditions.
• Make sure to keep your Tesla plugged in when at all possible. This allows Tesla to maintain target battery temperature levels and ensure you are preserving a target SoC.
• Using the scheduled departure, allows Tesla preconditioning to automatically warm the battery prior to a trip.

How to Maximize your Tesla Model S

Hopefully we’ve been able to provide some real clear cut data surrounding some of these hotly debated topics. As we’ve tried to show, each topic seems to present empirical data and user experiences that fall on both sides of each given topic. As you move forward in navigating your way through maximizing the longevity and efficiency of your Tesla battery, make sure you are taking advantage of all of the tools available to you that can provide clear insight and analytics.

Charging and keeping your battery healthy may seem complicated, but there are some applications that can help lighten the load. Optiwatt is a free app that helps you charge your car for the cheapest price, and will help you understand how to optimize your charging. Today, these various third party services enable Tesla owners to maximize their Tesla’s battery efficiency, longevity and even promote cost savings through optimizing battery charging and usage.