The duration a 4000mAh battery will last on a smartphone can vary based on factors like the smartphone’s hardware, software optimizations, screen brightness, usage patterns and network conditions. As a rough estimate, a 4000mAh battery can provide the following:

1. Light Usage: If you engage the phone for occasional calls, texts and light web browsing on a smartphone with a 4000mAh battery, you can get around 20 hours to 30 hours on a single charge.

2. Moderate Usage: Things change a bit here. With social media, occasional video streaming and general app usage, you can typically expect the 4000mAh battery to last approximately 12 to 14 hours.

3. Heavy Usage: If you’re using your smartphone intensively for activities like gaming, continuous video streaming and frequent GPS navigation, the 4000mAh battery might last around 5 to 7 hours.

4. Screen-On Time: If your phone screen is continuously active at high brightness, the 4000mAh battery will deplete relatively faster. Depending on the phone model and the apps you are currently engaging, it may last around 4 to 5 hours.