When Apple released the iOS 4.0 update, a number of iPod Touch owners found their battery life was significantly shorter. When we originally covered this issue, the solutions at the time were to turn off the Wi-Fi features, or use Airplane mode (which also turns off Wi-Fi), along with other similar suggestions that prevent network use.
Overall the problem was definitely caused by the use of Wi-Fi, but many assumed the error was in the device itself. While Apple's software update in no doubt was what started the problem, the root of the issue appears it might be an incompatibility between some routers' firmware and the way the iOS 4 update manages Wi-Fi connections.
Recently MacFixIt reader Lani Teshima wrote to the New York Times about her frustrations with the poor battery performance, and columnist David Pogue managed to get Lani in contact with an Apple engineering representative who spent about three weeks troubleshooting the problem.
Lani wrote in with the results of the troubleshooting efforts:
"I spent the last three weeks working closely with a rep from Apple's Corporate Executive Relations office to try to figure out exactly what the problem was that was causing the battery on my iPod Touch 2nd gen to die so quickly ever since I updated the iOS to 4.0/4.1. We tracked the actual battery usage and loss on my iPod Touch over several days, then had Apple Engineering analyze the log. The main culprit they suspected was the firmware on my wireless router. Their suggested fix? Update the firmware. When I updated the firmware on my wireless router, the battery issue was gone. My iPod Touch lasts for days with wifi enabled now, just like it did back when I was running iOS 3.1.3."
Many wireless routers are shipped with router software that is sometimes hastily thrown together, and that sometimes also may not be the best programmed code. As a result, there may be quirks and incompatibilities with some devices, especially as networking protocols are developed and implemented in devices. If you are experiencing poor network performance or the inability to maintain connections, in addition to obvious network overuse that is resulting in drained batteries on mobile devices, then you might look into troubleshooting the firmware.
If you have a different router available, try setting it up to see if there is any improvement when using it (especially if it is a different brand of router). Also try resetting your current router to default settings and see if a configuration refresh helps the issue, since sometimes the various security and access services in routers may conflict and lead to problems.
Additionally, as in the case with Lani, be sure to check for any firmware updates from the manufacturer of your router and apply them if they are available (be sure to closely follow the manufacturer's instruction on how to do so because interruptions during firmware updates can render devices useless).
Keep in mind that while a firmware update can fix the problem, sometimes one may also implement similar problems so if you have updated a router and are now having networking issues, you might look into downgrading the device's firmware. Sometimes companies have prior firmware versions readily available for download, but other times you may need to contact the manufacturer's customer support to obtain prior firmware revisions. At other times, once updated the firmware will not downgrade, in which case you may either need to wait for a new update or purchase a new router.