Calculate Charging Time: How Long Does Your Battery Take?
GOLISI Charging Time Calculator
mAh / mA · Real-time
Formula: Charging time ≈ Capacity / (Charge current × Efficiency)
Note: Efficiency is set to 85% by default. You can adjust it below if needed.
Tip: For an 80% charge, set Target SoC to 80.
Frequently Asked Questions: Battery Charging Time
How is charging time calculated?
The charging time is calculated using the formula: Charging time ≈ Capacity (mAh) ÷ (Charge current (mA) × Efficiency). For example, a 3,000 mAh battery charged at 2 A with 85% efficiency takes approximately 1 h 46 min. Actual times may vary slightly depending on cell chemistry, temperature, and battery age.
What does charger efficiency mean and why does it matter?
Charger efficiency describes how much of the energy drawn actually reaches the battery. No charger is 100% efficient — energy is lost as heat during the charging process. A typical Li-Ion charger operates at around 80–90% efficiency. The calculator uses 85% as a realistic default, but you can adjust this value to match your specific charger.
What is the difference between charging at 1 A and 2 A?
A higher charge current reduces charging time significantly. Charging at 2 A is roughly twice as fast as 1 A. However, higher currents can generate more heat and may slightly reduce overall battery lifespan over many cycles. For everyday use, 1 A is gentler on the cell, while 2 A is ideal when speed matters. Always check the maximum charge current specified for your battery.
What is the Start SoC and Target SoC setting?
SoC stands for State of Charge — the current charge level of your battery in percent. The Start SoC is how full the battery is before you begin charging; the Target SoC is your desired end level. For example, if your battery is at 20% and you only want to charge to 80%, the calculator factors in only that 60% range — giving you a much more accurate estimate for partial charging.
How long does it take to charge an 18650 battery?
A typical 18650 battery with 3,000 mAh charged at 2 A and 85% efficiency takes approximately 1 hour 46 minutes from 0 to 100%. At 1 A, expect around 3 hours 32 minutes. Golisi's O-Series and S-Series chargers support up to 2 A per slot, making them well suited for fast, safe 18650 charging.
How long does it take to charge a 21700 battery?
A 21700 battery typically has a capacity of around 5,000 mAh. At 2 A and 85% efficiency, the charging time is approximately 2 hours 56 minutes. Because of the larger cell size, using a charger with a 2 A output — such as the Golisi O2 or S2 — is particularly recommended.
Does the charging time differ between Li-Ion, Ni-MH, and Ni-Cd batteries?
Yes. While the formula for estimated charging time is the same, the actual chemistry behaves differently. Li-Ion batteries charge in a CC/CV process (constant current, then constant voltage), which can add time at the end. Ni-MH and Ni-Cd cells have different voltage curves and often require lower charge currents. The calculator provides a good estimate across all types, but always refer to your battery's datasheet for precise values.
Which Golisi charger is right for my battery?
- Needle Series (0.5 A): Compact USB charger for single cells — ideal for travel or low-demand use.
- O-Series / S-Series (2 A, 1 slot): Fast charging for 18650, 21700, and similar Li-Ion formats.
- I-Series (2 A, 1 slot / 1 A, 2 slots): USB-powered — flexible for use on the go.
- GL-Series (up to 0.5 A): Compact USB charger, great for AA/AAA Ni-MH cells.