Your battery is designed to retain up to 80 per cent of its original capacity at 500 complete charge cycles. If you have not completed the charging locations and still your battery does not provide enough backup then you can try re-calibrating your battery. Let your battery drain to 0% and then charge it to 100%. Once your battery is charged to 100% discharge the battery back to 0%. This will recalibrate the battery. Once you recalibrate the battery, use the phone normally and see if your battery is still draining too fast or taking time to charge. If the charging time has increased or if the battery does not last for long then you have to get your iPhone battery replaced.