Does Charging To 80 Percent Really Prolong Battery Life?

Does Charging to 80% Really Prolong Battery Life?

Charging your battery to 80% instead of 100% has been a long-standing debate, particularly among users of lithium-ion batteries found in phones, laptops, and electric vehicles. The practice is based on the premise that avoiding full charges and deep discharges can extend the lifespan of the battery.

The Science Behind Lithium-Ion Batteries

Lithium-ion batteries, the most common type used in portable electronics and electric vehicles, degrade over time due to various factors including charge cycles, depth of discharge, and charging voltage. Here are some key points:

Depth of Discharge (DoD): The smaller the discharge, the longer the battery will last. Avoiding full discharges (i.e., letting the battery drop to 0%) and instead keeping it within a moderate range (e.g., 20% to 80%) can significantly prolong battery life.
Charge Voltage: Raising the charge voltage above 4.20V/cell can shorten the battery's life. Every 0.10V drop below 4.20V/cell doubles the cycle life but reduces the usable capacity.
Cycle Life: Lithium-ion batteries have a limited number of charge cycles before they start to degrade. Keeping the battery between 20% and 80% charge can help in achieving more cycles before significant capacity loss occurs.

Practical Implications for Phones and Laptops

Phones:

Charging Strategy: Charging your phone to 80% and avoiding overnight charging can help prolong battery life. Apple introduced a feature in iOS 13 that charges the phone to 80% and then waits until just before you need it to charge it to 100%, which helps in reducing battery degradation.
Real-World Impact: For most users, keeping the battery between 20% and 80% is beneficial, especially if you plan to use your phone for more than two years. However, if you upgrade your phone frequently, this practice may not be as crucial.

Laptops:

BIOS Settings: Some laptops offer BIOS settings to limit battery charging to 80%. This is particularly useful if you keep your laptop plugged in most of the time. Limiting the charge to 80% can help in prolonging the battery's lifespan.
Calibration: It is also recommended to occasionally run your laptop on battery power until it completely drains and then recharge it to help keep the battery calibrated.

Electric Vehicles (EVs):

Built-In Limits: Some EVs, like the BMW i3, have built-in charge limits that prevent the battery from being fully charged or deeply discharged. This strategy helps in extending the battery's lifespan by avoiding the extremes of charge and discharge.
Usage Patterns: For EV owners who do not need the full battery capacity daily, keeping the battery between 20% and 80% can be beneficial. However, for long trips, it may be necessary to charge the battery to 100% despite the potential for reduced lifespan.

Fast Charging and Its Impact

Fast charging, while convenient, can be detrimental to battery health. High charging rates can cause increased heat and stress on the battery, leading to faster degradation. For example, a user reported a significant drop in battery life after using a 120W fast charger on their phone.

Best Practices for Battery Longevity

Avoid Full Charges and Deep Discharges: Try to keep your battery between 20% and 80% if possible.
Avoid Overnight Charging: Charge your device during the day and unplug it once it reaches 100% to avoid trickle charging.
Use Smart Charging Features: Utilize features like Apple's optimized battery charging or similar smart charging options available on some devices.
Monitor Temperature: Keep your device in a moderate temperature range (32°F to 113°F or 0°C to 45°C) to avoid heat-related degradation.
Calibrate Your Battery: Occasionally run your device on battery power until it completely drains and then recharge it to help maintain battery health.

By following these guidelines, you can significantly extend the lifespan of your lithium-ion batteries, making your devices last longer and perform better over time.