What’s the Minimum Battery Capacity for a Used iPhone 7 or 8 for Daily Usage?

When buying a used iPhone 7 or 8, it's crucial to evaluate the battery health and capacity to ensure good daily usage. Understanding these factors can help you make an informed decision and avoid potential disappointment. Let's dive into the details.

Battery Health and Daily Usage

Battery health refers to the condition of the battery in terms of how much charge it can hold compared to its original capacity. For a used iPhone 7 or 8, a battery health percentage of at least 80 is recommended. This indicates that the battery is still holding a reasonable charge and should provide decent daily performance.

Capacity Estimation

The original battery capacities for these models are as follows:

At 80% of its original capacity, the iPhone 7 would have around 1568 mAh, and the iPhone 8 would have approximately 1456 mAh. For perspective, an 80% capacity means the battery is still functional for normal daily use.

Real-World Battery Life

Realistically, a new iPhone 8 can provide about 9.5 hours of continuous use per charge. In comparison, the iPhone 7 can manage around 13 hours by the same measure. However, for simplicity, let's assume an average of 10 hours of continuous use for the iPhone 8. If the battery performs at 80% capacity, you can expect around 8 hours of usable time.

Generally speaking, anything over 8 hours of battery life is considered excellent. Between 6 to 8 hours is enough for most users to function normally. Therefore, the threshold for daily usability on the iPhone 8 would be around 60% battery capacity. For the iPhone 7, 46% capacity would equate to about 6 hours of use.

Potential Issues with Degraded Batteries

This calculation is theoretical. In practice, batteries that degrade below a certain point can start to fail rapidly. Batteries with a capacity below 50% may experience issues such as random shutdowns, fast draining, or faulty battery percentage updates. These issues can make the phone unresponsive or seemingly non-functional.

Many popular used phone retailers set a threshold of around 70% capacity for retail sales, but this varies significantly. Some retailers do not check the battery capacity or have any thresholds, but they usually offer a warranty or guarantee. Before making a purchase, check the terms and conditions of the warranty.

Testing Before Purchase

If you're buying from an individual, consider testing the phone for a few days to determine if it has any battery issues. Significant battery problems may become apparent quickly, allowing you to return the phone if needed.