Everyone should be aware of the tragic end to your mobile phone battery.
Calculating your cell phone's remaining battery life is difficult, first because you don't keep track of it, and second because you rarely charge it completely. Your cell phone may have 500, 800, or any number of charge cycles. In the first case, charging it once a day will not last more than two years; in the second case, it will last a year and a few months. In any case, this is the average battery life of your cell phone if it is fully charged and discharged daily. You can always do things to extend the battery life and make it last longer before replacing it.
It's important to note that the battery will not simply shut down or die at the end of its life cycle. It will gradually warn you when it is running low and needs to be replaced. It will last much less time, take longer to charge, and even if you use the phone less, it will only last a short time before prompting you to charge it. There may come a time when you need to charge it multiple times per day, or you may believe the charger isn't working because it's too slow. You may also notice some phone malfunctions due to insufficient power.
The battery capacity will gradually decrease, which you may not notice at first, but will become more noticeable over time. In some cases, depending on how long you've used it, you might actually notice the difference.
This can only happen when the battery reaches the end of its expected lifespan, and it may warn you ahead of time, or it may last much longer than the promised number of charges. Finally, this is an estimate; if you're lucky, your phone may last even longer without requiring a battery replacement. In the worst-case scenario, the phone will perform poorly, the battery will last significantly less time, and it may even fail, leaving you stranded at any time. You may also notice that you need to charge it more frequently each day.
At the first sign of trouble, you should consider replacing the battery. Fortunately, this isn't the most expensive repair, so if your phone is working well, replacing the battery is worthwhile. However, if your smartphone is experiencing other problems, isn't functioning properly, has a cracked screen, or is simply old, you might consider replacing it.
This might be more necessary in inexpensive mid-range or entry-level mobile phones. In the meantime, you can still use that battery without fear of anything happening; it won't explode or cause any damage to your phone. However, the sooner you consider replacing it, the better, as it could eventually fail.