A typical car battery stores between 600 and 1,200 watt-hours (Wh) of energy. To put that simply, it's enough power to run a 100-watt lightbulb for 6 to 12 hours. However, the "watts" a battery can provide at any given moment (its power output) is a different matter, often reaching 500 to 1,000 watts to crank an engine. The key measurement for energy storage is watt-hours (Wh), which is the battery's voltage multiplied by its amp-hour (Ah) rating.
For example, a common 12-volt battery with a 50Ah rating stores 12V x 50Ah = 600 Wh. The actual capacity depends heavily on the battery type. Traditional lead-acid batteries, used for starting engines, have lower energy density. In contrast, the larger lithium-ion batteries in electric vehicles (EVs) store dramatically more energy, measured in kilowatt-hours (kWh), where 1 kWh equals 1,000 Wh.
| Battery Type | Typical Voltage | Common Amp-Hour (Ah) Rating | Approximate Watt-Hour (Wh) Capacity | Primary Function |
|---|
| Standard Flooded Lead-Acid | 12V | 40 - 70 Ah | 480 - 840 Wh | Engine Starting |
| AGM (Absorbent Glass Mat) | 12V | 50 - 100 Ah | 600 - 1,200 Wh | Engine Starting/Deep Cycle |
| Lithium-Ion (EV Battery) | 400V | Varies (e.g., 50 kWh pack) | 50,000 Wh (50 kWh) | Vehicle Propulsion |
| Small Motorcycle Battery | 12V | 10 - 20 Ah | 120 - 240 Wh | Engine Starting |
It's crucial to understand that a battery should never be fully discharged, especially lead-acid types. Regularly draining it below 50% capacity can significantly shorten its lifespan. So, while a battery might have a 600 Wh capacity, its usable energy is much less if you want it to last.
