1. Vehicle type: Modern vehicles with a lot of electronic components tend to draw more power even when turned off, while older vehicles might have fewer power-draining features.
2. Battery age and condition: Older batteries or those in poor condition may lose charge more quickly when the car is not in use.
3. Weather conditions: Extreme temperatures, whether hot or cold, can affect battery performance and reduce its ability to hold a charge.
4. Electrical accessories left on: If any electrical accessories, such as interior lights or the radio, were left on, they could have drained the battery.
In general, if the car battery is relatively new and healthy, the car is a newer model with basic components (e.g., no touchscreens or power seats), the weather conditions are moderate, and no accessories were left on, there's a good chance the battery may still have enough charge to start the car after three weeks.
However, it's important to consider that car batteries do slowly discharge over time even when the car is off. After three weeks, particularly if any of the factors mentioned above (older battery, extreme weather, power-draining accessories) come into play, it's possible the battery won't have enough power to crank the engine.
If you're concerned about the battery, it's always best to connect a battery charger or use a jump-start (with assistance from another car or a portable jump starter) just to be sure before attempting to start the car.
