Li-ion Battery Discharge Rate Calculator
Understanding Li-ion Battery Discharge Rates
When working with Lithium-ion (Li-ion) batteries, understanding the discharge rate is critical for both performance and safety. The discharge rate, often referred to as the C-rate, determines how much current can be safely drawn from the cell relative to its total capacity.
What is the C-rate?
The C-rate is a measure of the rate at which a battery is discharged relative to its maximum capacity. A 1C rate means that the discharge current will empty the entire battery in one hour. For example, if you have a 3000mAh battery, a 1C rate is 3000mA (or 3 Amps). A 2C rate would be double that (6 Amps), resulting in a 30-minute runtime.
How to Use This Calculator
To find your battery's maximum discharge capabilities, follow these steps:
- Step 1: Enter the Battery Capacity in milliamp-hours (mAh). This is usually printed on the cell (e.g., 2500, 3000, 3500).
- Step 2: Enter the C-Rate. Check the manufacturer's datasheet for "Max Continuous Discharge Rate."
- Step 3: Click calculate to see the maximum current in Amps and the total runtime at that specific load.
Example Calculation
If you have a popular 18650 cell like the Sony VTC5A, which has a capacity of 2600mAh and a continuous discharge rating of 25A, you can calculate its C-rate by dividing the Amps by the capacity in Ah (25 / 2.6 = 9.6C). Conversely, if you know a battery is rated for 10C and has 2000mAh, the maximum current is 20 Amps (2.0Ah x 10C).
Safety Considerations
Never exceed the manufacturer's rated discharge rate. Over-discharging a Li-ion battery causes internal heat buildup, which can lead to thermal runaway, fire, or explosion. Always ensure your device's current draw is well within the limits of your battery's C-rate specs.