If you notice that your iPhone has been working allless and less after recharging, it does not mean that something has broken in it - it's just that the battery capacity has dropped in its battery. In any battery, the capacity decreases over time. In the iPhone it is initially within 1600 mAh, and in a year it will decrease to 900. This greatly affects the duration of the device without recharging. So if you do not want it to work for two or three hours, you need to do something like this every two years, like changing the battery.
Also, its capacity drops rapidly, if you havehabit of recharging the battery when it has not yet used its energy resources. So put the device on charging only when it really is needed.
Battery replacement is a very useful process,because after it your device will again be able to work very long. Therefore, do not neglect this from the principle of "better save", because sooner or later the capacity of the battery will drop to 200-300 mAh, and then the iPhone will turn off right during calls, and this is not very pleasant.
If you want to replace the batterycost you only at the price of the battery itself, then you can try to replace it yourself. But this is a rather risky undertaking. First, to dismantle the battery, you need to disassemble almost the entire device. Secondly, if you do it wrong, your warranty will automatically end, and you will lose both it and the iPhone. Therefore, if you are insecure in your abilities, it is better to entrust such a procedure to professionals - it will be much safer and not much more expensive.
With the change of battery is not worth it - it's badwill affect the operating time of the device. The most optimal interval for its replacement is one and a half to two years. During this time, the iPhone battery will work about twice as weak. On the other hand, battery replacement is expensive, so do not change too often. If you still want to save even more money, you can try to replace the battery manually.