C-rate expresses current relative to capacity. A short-duration rating needs its duration and conditions; it cannot establish a continuous rating.
Converting a C-rate into current
For a 20 Ah example, 1C corresponds to 20 A and 3C corresponds to 60 A. The one-hour scale used in the definition does not guarantee an actual one-hour operating time: voltage cutoff, load and temperature still matter.
I (A) = C-rate × Q (Ah) 3 × 20 Ah = 60 A
Reference: Texas Instruments · Drone / robot battery-management reference
Continuous operation and a time-limited peak
Describe a demand as a load sequence: normal operation, start-up or acceleration, peak duration, and recovery. Two loads with the same peak current can impose different requirements when their durations or repetition differ.
| Reference | Information to retain |
|---|---|
| Continuous current | Permitted duty, temperature, voltage limits and heat-removal conditions. |
| Short-duration current | Duration, initial SOC, temperature, cutoff voltage and recovery or repetition. |
| Charging rate | Charge method, SOC interval, voltage cutoff and termination. |
Reference: INL / US DOE · Battery Test Manual for Electric Vehicles
Power requires the operating voltage
Electrical power is voltage multiplied by current. A nominal-voltage calculation helps express an initial target, but the voltage under load is needed for an operating-power assessment. Peak power, usable energy and thermal behaviour are separate inputs to the evaluation.
P (W) = V_load (V) × I (A) Nominal example: 22.2 V × 60 A = 1,332 W
Questions to prepare
- What are the continuous and peak current or power targets?
- How long does each peak last, and how often does it repeat?
- What minimum loaded voltage and temperature limits must the system respect?
Common questions
Is the largest stated C-rate always continuous?
Check the definition. A maximum may refer to a limited pulse, SOC interval or test condition.
Does doubling parallel count double permitted pack current?
Ideal current arithmetic is only a reference. Connections, current sharing, protection and thermal limits require pack-level confirmation.