I found this on a CrunchGear comment
http://www.crunchgear.com/2008/07/18/review-iphone-3g/
Posted by Victor Healey
"BATTERY ISSUE FIXED
Simply FORCE a RESTORE in iTunes. The wrong firmware is in the orginal 3G phones. iTunes does not tell you that the firmware is incorrect at this time so do not bother the CHECK for UPDATES.
A FORCED RESTORE downloads the correct firmware from Apple and updates the 3G iPhone to the exact same version 2.0 (5A347)that is in the last batch to be sold this week.
In most cases it isnt worth trying to pull in a backup of your iPhone as most of these are corrupted. Just set it up as a new iPhone all over again and re sync to iTunes. You should notice that the battery issue is fixed immediately after a full charge an a useage cycle. After that try to keep the batttery charged as much as possible as it will last longer. Use the iPhone when connected to AC or on a car charger if at all possible to avoid using a portion of a discharge cycle. The iPhone battery has a life that is good for about 400 full discharge cycles.
The wrong firmware is iPhone firmware 2.0 (5A345)
The correct firmware is 2.0 (5A347)"
http://www.crunchgear.com/2008/07/18/review-iphone-3g/
Posted by Victor Healey
"BATTERY ISSUE FIXED
Simply FORCE a RESTORE in iTunes. The wrong firmware is in the orginal 3G phones. iTunes does not tell you that the firmware is incorrect at this time so do not bother the CHECK for UPDATES.
A FORCED RESTORE downloads the correct firmware from Apple and updates the 3G iPhone to the exact same version 2.0 (5A347)that is in the last batch to be sold this week.
In most cases it isnt worth trying to pull in a backup of your iPhone as most of these are corrupted. Just set it up as a new iPhone all over again and re sync to iTunes. You should notice that the battery issue is fixed immediately after a full charge an a useage cycle. After that try to keep the batttery charged as much as possible as it will last longer. Use the iPhone when connected to AC or on a car charger if at all possible to avoid using a portion of a discharge cycle. The iPhone battery has a life that is good for about 400 full discharge cycles.
The wrong firmware is iPhone firmware 2.0 (5A345)
The correct firmware is 2.0 (5A347)"