Use this calculator to estimate the true C rating of your LiPo Battery Pack. Check in to see how your RC LiPo battery pack performs when new or how it performs as it ages.
Using the RC LiPo Battery Pack C Rating Calculator
To use the calculator, 3 pieces of information is needed.
LiPo Battery mAh or capacity
Enter the capacity of your battery in to the first field within the calculator. This specification is labeled right on the front of the battery pack. Use only the spec listed value.
Highest Internal Resistance Cell within the LiPo
Enter the resistance of your LiPo battery as measured by your charger. Take the value value of internal resistance (IR) from all the cells within your battery pack. For example, if you have a 2 cell LiPo with an internal cell resistance of 2 milliohms and 4 milloms, the highest cell IR for the pack is 4 milliohms. The highest cell IR is to be entered in as milliohms. 1 milliohm = 0.001 ohms.
Follow these 3 steps for highest accuracy:
- The measurement must be done at room temperature. 22C or 72F. The pack should be at room temperature for 1 hour.
- It is recommended to take the measurement of your battery pack while being charged. The measurement should come from the first reading that your charger takes. (Within 3 minutes)
- Charge your LiPo battery pack for the reading at 1.5C, as long as this value is lower than the maximum recommended charge rate. Otherwise use the maximum charge rate of less than 1.5C. Start the charge with the pack between 20 and 40% capacity.
Battery packs Rated C Rating
Enter the maximum continuous discharge rating of the battery pack as specified on its label. Some LiPo’s provide a peak C rating and a maximum continuous rating on the label. The smaller C rating will be for continuous discharge.
Additional Considerations
The greatest chance for error in this calculation, comes from the internal resistance measurement. Internal Resistance tends to drop as the cell heats up while continuing to be charged. We take the first initial reading as a means to create a standard for the test. In addition, it is the simplest way to reach a steady state measurement conclusion quickly.