What Is the Battery State of Health (SOH) & Degradation Calculator?
State of Health (SOH) benchmarks remaining battery performance against original new cell specifications.
How Does the Battery State of Health (SOH) & Degradation Calculator Work?
Evaluates capacity loss caused by solid electrolyte interphase (SEI) growth and loss of active lithium ions.
Battery State of Health (SOH) & Degradation Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
\text{SOH}_C = \frac{C_{\text{curr}}}{C_{\text{init}}} \times 100\%, \quad R_{\text{growth}} = \frac{R_{\text{curr}}}{R_{\text{init}}}
Capacity retention percentage and internal resistance growth factor.
How to Use the Battery State of Health (SOH) & Degradation Calculator
- Input current measured Ah capacity, initial rated Ah capacity, and initial/current internal resistance.
Step-by-Step Example Calculation
EV Fleet Battery Diagnostics
Input Values:
measuredCapacityAh:42
initialRatedCapacityAh:50
measuredInternalResistanceMOhm:30
initialInternalResistanceMOhm:20
Worked Steps: Capacity SOH is 84.0% with 1.50× internal resistance growth (in-service healthy status).
Understanding Your Result
Shows capacity SOH, resistance growth factor, and whether End of Life has been reached.
Factors That Affect the Result
- High ambient temperature, high charging C-rates, and sustained high state of charge accelerate SOH decay.
When Should You Use This Calculator?
- EV battery warranty claims, second-life energy storage repurposing, and preventative maintenance.
Assumptions & Limitations
- Measurements must be taken at normalized reference temperature (25 °C).
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard diagnostic protocol aligned with SAE J1798 and ISO 12405.