For lithium-polymer (LiPo) batteries, such as those used in smartphones, it is generally recommended to follow best practices for battery maintenance rather than focusing on specific charge thresholds. Here’s a summary of the best practices for charging LiPo batteries in smartphones:

**1. Avoid Deep Discharges:

• 20% Battery: It’s okay to charge your smartphone when the battery level is around 20%. Lithium batteries, including LiPo, do not need to be fully discharged before recharging. In fact, deep discharges (below 20%) are not ideal for the long-term health of the battery.
• Recommended Range: Ideally, try to keep the battery level between 20% and 80% for optimal battery health. Frequent deep discharges can accelerate battery wear.

**2. Partial Charging is Fine:

• Top-Up Charging: You don’t need to wait until the battery is completely drained before recharging. Frequent top-ups are fine and are often better for maintaining battery health compared to letting it fully discharge and then fully charge.
• Avoid Full Discharges: Fully discharging a LiPo battery regularly can reduce its lifespan. It’s better to recharge when the battery is partially depleted.

**3. Charging Practices:

• Charge Regularly: It’s good practice to charge your smartphone when it reaches around 20% to 30% rather than letting it drop to critically low levels.
• Avoid Overcharging: Modern smartphones and chargers are designed to stop charging once the battery reaches 100%, so overcharging is not a significant concern. However, maintaining a battery level in the range of 20%-80% can be beneficial for battery health.

**4. Battery Management:

• Battery Calibration: Occasionally allowing the battery to drain to around 5-10% and then fully charging it can help recalibrate the battery management system. This is not required frequently but can be done every few months.
• Heat Avoidance: Avoid charging the phone in hot environments or using it heavily while charging, as excessive heat can degrade battery life.

**5. Avoid Extreme Conditions:

• Temperature: Keep your smartphone and battery away from extreme temperatures, as heat and cold can negatively impact battery performance and longevity.

Summary:

• Charging Threshold: Charging your smartphone when the battery is around 20% is perfectly fine. There’s no need to wait until it’s critically low.
• Optimal Range: Maintaining battery levels between 20% and 80% is generally recommended for long-term health.
• Frequent Charging: Regular partial charging is beneficial and more practical than deep discharges.

By following these practices, you can help extend the lifespan and performance of your LiPo battery in your smartphone.