What is battery state of charge (SOC)?
State of charge is the percentage of battery capacity that remains available. A 100% SOC means the battery is fully charged, while 0% means completely discharged. See also our calculate Lithium-Ion Battery Total Pack Capacity.
How do I measure battery voltage for SOC calculation?
Measure the open circuit voltage when the battery has been at rest for at least 2 hours without charging or discharging. Use a quality digital multimeter for accurate readings.
Why does temperature affect battery SOC calculations?
Battery voltage changes with temperature. Cold temperatures reduce voltage readings while warm temperatures increase them, so temperature compensation ensures accurate SOC calculations.
What's the difference between SOC calculations for different battery types?
Each battery chemistry has different voltage curves. Lead acid batteries have different voltage-to-SOC relationships compared to lithium-ion or nickel-based batteries.
At what SOC should I recharge my battery?
For lead acid batteries, recharge at 50% SOC to prevent damage. Lithium-ion batteries can be discharged deeper, typically to 20-30% SOC safely.
How accurate are voltage-based SOC calculations?
Voltage-based SOC calculations are reasonably accurate for rested batteries but can vary by ±5-10% depending on battery age, temperature, and load history.