EV Battery Engineering Calculator
The math inside every EV battery: energy from voltage and capacity, charging current from power, and why 800V systems charge so fast.
400V most EVs · 800V new platforms.
at this power, ~8% loss
400V vs 800V architecture
| Property | 400V (most EVs) | 800V (IONIQ 5, EV6, Taycan) |
|---|---|---|
| Current at 350 kW | ~875 A | ~440 A |
| Typical max charge | 150-250 kW | 250-350 kW |
| 10-80% time | ~30 min | ~18 min |
| Cable weight & heat | Heavier, hotter | Lighter, cooler |
Frequently asked questions
How do I calculate battery energy from voltage and capacity?
Energy (kWh) = voltage (V) × capacity (Ah) ÷ 1000. A 400V, 150Ah battery holds 60 kWh. This is the same math used to size battery packs.
What voltage do EV batteries run at?
Most EVs run 350-450V systems, while new 800V platforms (IONIQ 5, Taycan, EV6) run ~800V to enable faster charging and lighter cables.
How do I calculate charging current?
Current (A) = power (W) ÷ voltage (V). A 7 kW charger at 230V draws ~30A. A 350 kW charger at 800V draws ~440A — why DC cables are huge.
What is a kWh and how much is it?
A kWh is 1,000 watt-hours — the energy to power a 1 kW device for an hour. A 60 kWh battery can deliver 60 kW for one hour or 7 kW for ~8.5 hours.