Faster charging isn’t just about bigger plugs — it’s about physics. Current, voltage, heat, and the chemistry inside the cell all set hard limits. Understanding why some EVs charge in 20 minutes and others take an hour comes down to a few key ideas. Here’s the physics behind faster charging.
Power = Voltage × Current
Charging power is voltage times current. To add more power you can raise voltage, current, or both. Early fast chargers pushed high current at modest voltage; newer systems (e.g. 800 V architectures) raise voltage so they can deliver more power without absurdly thick cables and cooling. That’s why 800 V cars can sustain higher charging rates: same current, more voltage, more power. The trade-off is that the whole system — battery, cables, connectors — has to handle it.
Heat Is the Enemy
Resistance in the cell and in the wiring turns current into heat. Push too much current and the battery heats up; too much heat degrades the cell and can force the car to throttle charging to protect the pack. So “faster charging” depends on thermal management: cooling the pack (and sometimes the cables) so you can sustain high power without overheating. Better cooling and better cell design (lower internal resistance) are what let newer EVs hold high charge rates for longer.
Chemistry and C-Rate
Cells have a “C-rate” — how fast they can accept charge relative to their capacity. A 1C rate means full charge in about an hour; 2C means roughly 30 minutes. Not all chemistries can do high C-rates without damage or loss of cycle life. LFP and some high-nickel NMC formulations are tuned for faster charge acceptance. The physics is in the electrodes and electrolyte: how quickly ions can move in and out without plating or degradation. Faster-charging cars are often using chemistries and pack designs optimised for that.
The Curve Matters
Batteries don’t charge at constant power. They typically take more power when the state of charge is low and taper as they fill. So “20 minutes to 80%” is a common spec — the last 20% is slower by design to protect the cell. Faster charging in practice means a high, sustained rate through the middle of the curve and good thermal management so the rate doesn’t drop too early. The physics sets the ceiling; engineering (thermal, BMS, chemistry) determines how close you get.
Bottom Line
Faster charging comes from higher voltage and current within thermal and chemical limits. Better cooling, lower-resistance cells, and chemistries that accept charge quickly let EVs push closer to those limits. The physics is simple; the engineering is what makes it work in the real world.
