How does the battery life of the iPhone 3G compare to the original iPhone in real-world tests? Can you replace the battery in the iPhone 3G?

Apple reports that the iPhone 3G provides modestly better battery life than the original iPhone. In particular, Apple claims that the iPhone 3G can provide "up to" 10 hours of talk time while using a 2G network (compared to 8 hours for the original) and 300 hours of standby time (compared to 250 hours for the original).

However, Apple also notes that the iPhone 3G only provides 5 hours of talk time or web use on a 3G network. Other reported battery life estimates for web use over wi-fi, video playback, and music use are identical for the original and iPhone 3G -- six, seven, and 24 hours, respectively.

In the first major review to hit the web, the always excellent Walt Mossberg ran his own battery tests using 3G and reported:

Although I left the Wi-Fi function on, I didn't connect it to a network, so the phone had to rely on 3G. In my test of voice calling, I got 4 hours and 27 minutes, short of Apple's maximum claim and nearly three hours less than what I recorded in the same test last year on the original iPhone [using the slower EDGE network]. In my test of Internet use over 3G, I got 5 hours and 49 minutes, better than Apple's claim, but far short of the nine hours I got using Wi-Fi in last year’s tests.

More important, in daily use, I found the battery indicator on the new 3G model slipping below 20% by early afternoon or midafternoon on some days, and it entirely ran out of juice on one day. I overcame this problem by learning to use Wi-Fi instead of 3G whenever possible, turning down the screen brightness and even turning off 3G altogether, which the phone permits.

In its characteristic extensive testing, AnandTech also reported similar numbers:

Battery life with 3G enabled was 4 hours and 44 minutes, down from nearly 6 hours when I tested the original iPhone. Turning off the 3G modem and switching to Edge, my call time went up to 6 hours and 4 minutes, about where it should be based on my original iPhone test results. With less than 5 hours of talk time, if you plan on doing a lot of talking you had better shut off 3G mode on the iPhone.

The well-respected iLounge likewise had similar results, but found this to be considerably less acceptable:

If you're willing to just avoid using the 3G phone and data services you're forced to pay extra for, the iPhone 3G will work better than its predecessor; use 3G, and you'll fall well short of last year’s numbers. From our perspective, this drop in call performance is unacceptable by phone standards, as it means that active 3G users will need to recharge the device twice a day. . .

Unlike the iPod touch, customers are buying this as a communications device, and for that purpose, it runs much shorter than its predecessor between charges. More charging means more of a need to replace the battery, and less convenience for the user. Under the circumstances, and especially given that it already expanded the iPhone in every physical dimension, Apple should have done the right thing and further increased the battery's capacity, or offered an extended battery with a user-replaceable back plate. As it hasn't, potential buyers should pass on iPhone 3G in favor of a more power-efficient sequel, or be prepared to do lots of charging, then request a replacement battery before the end of the warranty period.

In a great "tear down" that is well worth digging through, the always comprehensive iFixit was delighted to discover that the battery in the iPhone 3G -- although certainly not "swappable" or exactly easy to replace -- is not soldered as it is in the original iPhone, which makes replacing the battery comparatively simple.

Ultimately, the battery life of the iPhone 3G is better than that provided by the original iPhone if using the older 2G/EDGE network but inferior if using the newer 3G network. This is to be expected given the power requirements of the 3G technology. Some heavy users may find the battery life of the iPhone 3G to be inadequate and wish that Apple made it possible to quickly swap batteries as is possible for other 3G phones on the market, but at least Apple has made replacing the battery possible without resorting to soldering.

Just as the company does for the original iPhone, after the one year warranty, Apple offers to replace the battery for US$79 plus US$6.95 for shipping. The service takes three business days and a "loaner" iPhone is offered for US$29 while the battery replacement is in progress.

Also see: What is the battery life of the original iPhone? Can you replace the battery?