The watt-hour (Wh) capacity of a car battery varies dramatically depending on its type. A typical lead-acid starting battery found in most gas-powered cars holds roughly 600 to 800 watt-hours. In contrast, the large lithium-ion traction batteries in electric vehicles (EVs) store 50,000 to 150,000 watt-hours or more. The key difference is that a starter battery is designed for short, high-power bursts to crank the engine, while an EV battery is built for sustained energy delivery to power the vehicle.
To understand this, you need to know two figures: Voltage (V) and Amp-hour (Ah). The watt-hour capacity is calculated by multiplying these two values (Wh = V x Ah). For example, a standard 12-volt car battery with a 50Ah rating has a 600Wh capacity (12V x 50Ah = 600Wh).
Here’s a comparison of common battery types and their typical energy capacities:
| Battery Type | Common Voltage | Typical Amp-Hour (Ah) Capacity | Approximate Watt-Hour (Wh) Capacity | Primary Function |
|---|
| Lead-Acid (Starting) | 12V | 40 - 70 Ah | 480 - 840 Wh | Engine cranking |
| Lead-Acid (Deep Cycle) | 12V | 50 - 200 Ah | 600 - 2,400 Wh | Powering accessories (e.g., RVs, boats) |
| Lithium-Ion (Hybrid EV) | 200V - 300V | 5 - 10 Ah | 1,000 - 3,000 Wh | Assisting engine & regenerative braking |
| Lithium-Ion (Full EV) | 350V - 800V | 100 - 300 Ah | 50,000 - 150,000+ Wh | Propelling the vehicle |
When discussing a traditional car battery, the Cold Cranking Amps (CCA) is a more critical metric than watt-hours, as it measures the battery's ability to start an engine in cold weather. For EVs, the watt-hour rating, expressed in kilowatt-hours (kWh), is the standard measure of range, similar to the size of a gas tank.
