Your phone’s battery is arguably the most important piece of hardware on the device, considering that it is the main source of power. Many smartphone users have no basic understanding of how batteries work instead they only want their batteries to last longer. To have a basic understanding, it is vital to first understand the basic terminology like mAh. You must be wondering why this abbreviation has a weird spelling. The A is capitalized because, under the International System of Units, “ampere” is always represented with a capital A. The term mAh is an abbreviation for “milliampere hour,” and it’s a way to express the electrical capacity of small batteries such as the one on your phone.
To understand more about mAh, we need to borrow some basic knowledge from physics. mAh is calculated by multiplying the amount of time the battery lasts by the amperes of the discharge current. For non physicists, this may sound complicated but it's quite simple. If you have a battery of say 1000mAh, and you connect it with a load that drains 1000 milliampere per hour, then it will be reduced to zero percent in exactly one hour. This implies that for a battery of say 10,000 mAh, connected to a load draining 1000 milliamperes per hour, it will be drained to zero percent in ten hours.
With that basic understanding, you can note that the larger the mAh of a battery, the more it will last. A factor to keep in mind is that not all phones drain at the same current. Some drain faster and therefore will drain a larger battery faster. The device usage is also another factor to keep in mind. When your device is in heavy use, it is more likely to drain more in a short period of time.