Why Shouldn’t You Charge EV to 100%?

Do you always wait until your phone reaches 100% before unplugging the charger? This charging habit is also applied to electric vehicles, with many EV owners maintaining the mindset that “only charging EVs to 100% can bring peace of mind.”

But in reality, electric vehicle batteries are somewhat similar to phone batteries, and keeping them fully charged for long periods is actually not good. The optimal EVcharging level for an electric vehicle battery should be maintained at around 80%. Why is that?

80% Rule for EV Charging

For routine driving, maintaining your EV battery between 20% and 80% is widely considered best practice. This guideline is based on how lithium-ion batteries (used in modern-day EVs) respond to repeated charging cycles.

When charge EV to 100% or deeply discharging it to 0%, the internal battery voltage rises sharply, placing additional stress on the battery cells. It will shorten its lifespan. At high charge levels (90%-100%), fast charging and high-temperature environments can further accelerate EV battery degradation.

Just as people shouldn’t binge eat, batteries also need moderate charging to avoid extreme conditions.

Why Shouldn’t You Charge EV to 100%?

Below is a detailed breakdown of “Why only charge EV to 80?” based on electrochemical principles, temperature, safety, and charging time.

1. Electrochemical Principles of EV Batteries

Electric vehicles mostly use lithium-ion batteries. Energy is stored and released via the movement of lithium ions between the cathode and the anode. When charge EV to 100%:

Lithium ions continuously deintercalate from the positive electrode.
The negative electrode (graphite) may accumulate lithium metal, forming dendrites that can pierce the separator, leading to short circuits or capacity loss.
Under high voltage, the electrolyte is more prone to side reactions, generating gases and solid deposits, which degrade battery performance.

Thus, if you charge EV to 100% for several times, the battery life will gradually decrease.

2. Temperature Factors

Heat generation increases significantly during charging, particularly in the final phase, as heat dissipation cannot occur promptly. In a hot summer, the temperature rise becomes even more obvious. High temperatures accelerate side reactions within the battery, leading to accelerated ageing.

3. Safety Risks

At full charge, the battery operates under high internal pressure. In the event of a collision or short circuit, the risk of thermal runaway increases dramatically. This condition may lead to uncontrolled heating or fire.

To reduce this risk, most automakers set aside about 4%-5% of the battery’s capacity as a safety buffer, so a displayed 100% battery is not truly full. Nonetheless, frequent full charges put an unnecessary burden on the battery and elevate safety risks over time.

4. Charging time

Another reason why it’s not recommended to charge EV to 100% is that the charging power drops after reaching 80%, resulting in less range gain but significantly longer charging time.

This happens because the battery doesn’t absorb energy at a constant rate. When the charge level reaches 80%, the Battery Management System (BMS) automatically reduces the charging current to prevent overcharging and overheating, causing the final 20% charge to take considerably longer.

For example, while it might take only half an hour to charge your car from 0% to 80%, the last 20% could still require another half hour or even more. It makes charging 80% of a battery the better choice.

Exceptions: When is it Recommended to Charge EV to 100%?

So you may ask, should I charge my EV to 100% in some specific situation? Yes, there are specific cases where a full charge is both appropriate and beneficial. These situations include:

1. Before Long-Distance Trips

If you are stepping out for an extended trip, charging EV to 100% helps you achieve the maximum possible distance in a single charge. This reduces the frequency of finding charging stations and allows for more efficient trip planning.

2. In Remote Areas with Limited Charging Stations

In mountainous areas, deserts, or remote highways, each charging point is spaced far apart, and sometimes there are no available charging stations at all. Charge EV to 100% becomes crucial to ensure your vehicle can reach the destination or the next charging point. Additionally, it helps alleviate range anxiety, allowing drivers to travel with peace of mind.

3. Other Scenarios Requiring Higher Energy Consumption

Certain conditions, such as towing, carrying heavy loads, or driving in extreme cold or hot weather, increase energy demand. A full charge in these situations ensures the vehicle can operate without unexpected range limitations.

So if you wonder “How often should I charge my EV to 100,” the answer is that it should only be the case when you think it’s absolutely necessary to get a longer range.

Driver’s Guide: How to Charge Scientifically?

An optimised charging routine, based on daily needs and environmental conditions, is crucial for extending the life and performance of an electric vehicle. Here is how to recharge your EV in an efficient manner.

1. Daily Usage Suggestions

For daily commuting, setting the charging limit to 80% is strongly recommended. This range is enough for most daily driving needs and helps minimise stress on battery cells.

Slow charging methods, such as Level 1 or Level 2 AC charging, are preferable for regular use. They deliver energy at a moderate rate, generate less heat, and contribute to long-term battery stability.

2. Long-term Parking Strategy

If the vehicle will remain idle for several days or weeks, it’s better to maintain the battery level between 40%-60%. This prevents both deep discharge and prolonged exposure to high voltage, which can lead to capacity loss.

3. Additional Tips to Extend Battery Life

Charging in high temperatures accelerates battery degradation. Whenever possible, schedule charging during cooler hours, such as early morning or overnight.

Many EVs allow users to program charging times to align with off-peak electricity rates, reducing both thermal impact and energy costs. Parking in shaded or temperature-controlled areas further supports battery preservation.

Where to Invest in Smart Charging Stations?

For EV owners who want greater control over charging habits, or for commercial charging point operators looking to attract customers through smart charging services, BENY provide smart and efficient solutions. These include:

Level 2 EV chargers support monitoring and managing charging sessions via mobile apps. Features include charging reservation, maximum current settings, real-time status monitoring, and the dynamic load balancing function, making them ideal for home charging.
Level 3 EV chargers offer power ranging from 20kW to 600kW. In addition to the above smart features, they adopt a modular structure to simplify installation and maintenance. Multiple EV charger protection methods and outstanding heat dissipation performance also enhance the competitive advantage of commercial charging points.

All these features make it easier to follow the recommended 20% to 80% range for daily use.

Final Words

Keeping the battery at a 20% and 80% level for daily use is an optimised charging method to extend battery life. For easy control over charging limits and real-time monitoring, BENY’s smart charging stations provide a reliable solution. With real-time monitoring, adjustable charge limits, and wide compatibility, we make it easy to maintain the ideal charging range.

Contact us now to optimise your EV charging!