Understanding Battery State of Health: Key to Longer Lifespan

Battery state of health (SOH) measures the current condition of a battery compared to its ideal performance at newness. It’s a critical metric for smartphones, laptops, electric vehicles, and energy storage systems, directly influencing usability and reliability.
In 2025, as portable devices and EVs dominate daily life, understanding SOH helps users extend battery life, avoid sudden failures, and make informed device upgrades. This guide explains what SOH means, how to measure it, and practical steps to keep your battery healthy.

What Is Battery State of Health?

State of health refers to the battery’s maximum capacity relative to when it was new, usually expressed as a percentage. A healthy lithium-ion battery typically holds 80–100% capacity at launch, dropping gradually over hundreds of charge cycles. By 2024–2025 standards, consistent SOH above 80% is considered excellent, while anything below 70% signals degradation requiring attention.

How to Measure Battery SOH

Several methods help assess SOH:

• Manufacturer diagnostics: Most devices include built-in tools (e.g., Android Settings > Battery > Battery Health) that report SOH using internal impedance tests and charge-discharge cycles.
  
• Third-party apps: Tools like AccuBattery or CoconutBattery analyze real-time usage patterns, charge cycles, and voltage to estimate SOH more precisely.
  
• Laboratory testing: For commercial or EV batteries, advanced electrochemical impedance spectroscopy (EIS) and cycle life tests provide industry-grade SOH results—though these are impractical for average users.

Common Causes of SOH Degradation

Several factors accelerate battery aging:

• High temperatures: Prolonged exposure above 35°C (95°F) speeds up chemical breakdown inside cells.
  
• Deep discharges: Repeatedly letting the battery drain to 0% strains electrodes and reduces cycle life.
  
• Fast charging stress: While convenient, frequent fast charging (over 60°C) increases heat buildup and lithium plating, degrading capacity over time.
  
• Storage conditions: Storing batteries at 100% charge or in cold environments accelerates self-discharge and internal damage.

Practical Tips to Maintain Battery Health

To maximize SOH and extend device life:

• Avoid extreme temperatures—use devices in 15–30°C (59–86°F) environments.
  
• Keep charge levels between 20–80% for daily use; avoid full 100% charges unless storing long-term.
  
• Enable adaptive battery settings to limit background app activity and reduce unnecessary power draw.
  
• Perform occasional full charges and deep discharges (down to 10–20%) every 3–6 months to recalibrate battery management systems.
  
• Use original chargers and avoid third-party adapters that lack intelligent charging controls.

Real-World Impact of SOH on Device Performance

A battery with 75% SOH delivers up to 25% less runtime than a fresh one. Smartphones may show