Voltage, capacity, C-rate and energy
The four numbers that describe any cell, and how they connect.
- Explain voltage, capacity, c-rate and energy at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real pack
Overview
Get fluent with these four quantities and every specification sheet, charging curve and warranty clause becomes readable.
In depth
1C empties or fills the cell in one hour; 3C does it in twenty minutes.
Voltage / Current Calculator
Ohm's law and DC power for high-voltage system sizing.
P = V × I ; I = P ÷ V ; R = V ÷ IRaising system voltage lowers the current needed for the same power, which is why 800 V architectures can use thinner, lighter cables and charge faster without overheating.
Example: 150 kW at 400 V needs 375 A; at 800 V only 188 A.
- Cable heating scales with I², so halving current quarters the losses.
- DC rapid cables above ~200 A are usually liquid-cooled.
- Contactors and fuses are rated by current, not by power.
Cells in series multiply voltage; cells in parallel multiply capacity. Energy is the same either way — but voltage decides how much current your cables must carry.
Key takeaways
- C-rate normalises current against pack size.
- Series raises voltage, parallel raises capacity.
- Higher pack voltage means lower current for the same power.
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