Cell phone batteries can last just a year or many years, but it comes down to how well you take care of them. If your phone is acting up, it might be time for a new battery. Many people keep batteries a lot longer than is advisable because they don't want to shell out for something they feel like they just purchased. Not replacing your batteries, however, can end being more costly--or even potentially harmful.
Charge your battery fully and time how long it takes for it to drain. Properly working batteries should maintain at least some charge for 24 hours. If your battery is draining in only 24 minutes, that's a good indicator it's time for a new one.
Check to see if your battery wobbles. Cell phone batteries have altered over the last few years into completely flat casings. Set your battery down on your desk and see if it wobbles. When batteries are worn out, they compress, creating somewhat of a curve. Properly functioning batteries will lie completely flat, whereas batteries that need to be replaced will wobble.
Spin your battery. Sometimes it can be tough to tell if the wobble is natural or caused by human interference. An easy way to double-check is for you to spin your battery. Perfectly flat batteries will not spin, so if your battery does not spin you know it is working correctly. Put your finger on one corner of the battery and spin it. If it spins, it's time to replace your battery right away.
Analyze your charging habits. There are many different schools of thought when it comes to how best to charge your battery. One thing that maintains general consensus, however, is that you should not allow your battery to drain all the way before recharging it. This puts an added strain on the battery and decreases its life. Constantly recharging your battery will also wear it out. If you've still got half a battery left, you don't need to recharge it. All of these things could contribute to your battery dying much sooner than you anticipated.
Don't ignore damage. A lot of myths go around about the ability to "save" dropped batteries, cracked batteries, batteries that have been drowned in water, etc. Ignore all of them. If your battery is damaged, it is time to replace it. Damaged batteries can explode, releasing battery acid and other kinds of harmful things. Even if it looks as if you can save it, the internal damage may be too great to see. The money spent on the new battery will be less than the money spent repairing the results of a major battery malfunction later on.
Replace your battery with a newer battery if you have access to one. Oftentimes friends will have the same phone, and you can test your phone with someone else's battery. If it functions properly, your battery will need changing. If it doesn't function properly, the problem may lie within your phone and have nothing to do with your battery itself.
After about two years, you should begin looking into replacing a battery. Even the most well-maintained batteries die and need to be swapped out.
Recycle your old batteries when you replace them. Some stores offer rebates as an incentive to do so.