I have recently upgraded my one year old iPhone 3GS to the latest firmware 4.2.1, after which I have jail-broken it using Redsn0w 0.9.6b5 tool. Because I am using an iPhone in India which I bought in USA, I have also unlocked the carrier using the Ultrasn0w tool. After I upgraded it from my previous 3.0 firmware, which was quite old and obsolete in one year, I realized a great speed and functionality change on my iPhone 3Gs. But one major problem I noticed was my battery was draining like anything !
For two days I was totally annoyed because of the battery draining issue, on keeping my phone on overnight, battery levels went down as much as 30 to 35 % compared to earlier 5 to 8 % earlier on my previous firmware. On some quick research online and checking some forums, I got some solutions which actually solved my problem. In this post, I will share with you how I fixed the battery drain problem with jailbroken iPhone 3GS running on 4.2.1 firmware and iPad baseband 6.15.
To check which firmware is running on your iPhone, you can go to Settings > General > About. As you can see below, my iPhone is running 4.2.1 with jail broken iPad baseband modem firmware 06.15.00 which can be unlocked with ultrasn0w tool available in Cydia.
Fix 1 : Hard Reset –
To fix the battery draining issue, first thing you should try is to hard reset your iPhone. To hard reset, hold the power and home button for a few seconds and your iPhone screen will go blank. This will cut off the power to the phone, now release both the buttons. Leave the iPhone blank for 10 seconds or so to let it turn off completely. Now click the power button only just for a few seconds when Apple logo shows on your iPhone, give it a few minutes to boot completely. This should fix the battery drain problem for most of the iPhones. Use your phone for a day or two to observe if the battery drain problem has been resolved or not. In my case, hard reset solved my iPhones battery problem. If it doesn’t fix your problem, you can try the fix 2 and fix 3 mentioned below.
Fix 2 : Reset Network Settings
In some cases some there may be a bad network setting causing the battery to drain, to solve this issue, you can rest the network settings to default values. Before you do that, note down any custom settings or APN, VNP and other settings which you might have added in case you need to refer those settings in future.
To reset the network settings, go to Settings > General > Reset > Reset Network Settings on your iPhone. After this turn off and turn on your iPhone. This will fix any bad or corrupt setting.
Fix 3 : Re-Activating the SIM
We have not tested this solution, so do this at your own risk. Go here for the instructions to install a Cydia app called SAM and SAMPrefs which is used for activation of SIM.
Hope this will help you reclaim the iPhone battery life running iOS 4.2.1 with baseband 06.15.00