C-rates are a common way to normalize charge or discharge currents among dissimilar chemistries or form factors.
On the left plot is a common test protocol to charge or discharge a cell at various rates, in order to characterize its rate performance. These rates are often programmed as absolute currents, like 1A, 2A, or 5A. However, it can be advantageous to analyze the rates in terms of C-rates instead of amps, as shown on the right plot.
A C-rate is the rate divided by the capacity. For example, a cell with a capacity of 5 amp-hours being discharged at 10 amps has a C-rate of 10A/5Ah = 2C. The advantage of using C-rates is that it allows an apples-to-apples comparison across different chemistries, form factors, and suppliers.
Try Plotting It Yourself:
1. Select some test data in Voltaiq that has multiple rates
2. Select 'Maximum Discharge Current' for the X axis and 'Discharge Capacity' for the Y axis
4. Under 'Normalization & Transforms', choose 'Normalize x-Axis' by 'Constant'
5. Enter in the value of the nominal 1C capacity (in this case, 2.938Ah)
6. Add a negative sign if it is a discharge rate, or positive sign if it is a charge rate
7. Click generate
Make Life Easier With Metadata
Instead of entering in a numeric value for the nominal capacity each time, you can conveniently tell Voltaiq to use the cell's nominal capacity.
This is a feature that is enabled by setting up a metadata ingestion so that Voltaiq has each cell's key metadata, such as capacity, active material mass, or loading. Contact us at support@voltaiq.com and we can help you get your metadata ingested!