Optimize your iPhone 3G Battery Life

Updated 16 Nov 2008: Fully charged battery indicator
Updated 29 Dec 2009: Added turning off of Notifications


Finally have time to write down some of my optimization tips for my iPhone 3G battery life. With an above-average usage of the iPhone 3G (some people think I'm a heavy usage user), the iPhone will last me about 2 days on a charge. On a low volume day, it's about 3 days on a charge.

The tip is very simple. All you need to do is to turn off your 3G/Wi-Fi/Bluetooth by default. To turn it off, do the following:

1. Tap on Settings > General > Network
2. Turn OFF the Enable 3G option
3. Tap on Wi-Fi
4. Turn OFF the Wi-Fi option
5. Tap on General (back) > Bluetooth
6. Turn OFF the Bluetooth option
   

For the newer iPhone OS 3.0. All you need to do is to turn off your Push Notifications. To turn it off, do the following:

1. Tap on Settings > Notifications
2. Turn OFF the Notifications option

That's it. To re-enable it, follow the same steps above, but turn the option ON instead. To further save on your battery life, refer to this tip on reducing the brightness of your iPhone here.

That's the simple part. Now the explanation on why this works. Reasons:

1. 3G is a huge battery drain on any type of phone. I have friends using Nokia and Sony Ericson and they tell me that the phone usually lasts them only about a day.
   
   
2. 3G Network blindspots makes the iPhone 3G works harder, draining its battery life.
   
   This is technically how I think the iPhone works. Basically if you enabled the 3G option, the iPhone will always try to connect to the 3G Network. However, regardless of what your telco say, the 3G network coverage does not completely cover the whole area. It has its blind spots.
   
   The problem comes when you hit the blindspot. For example, in Singapore's underground MRT stations. Underground, the EDGE network is the strongest. If you have enabled your 3G network, the iPhone will constantly try to connect to the 3G network while you're underground, although it is unable to find a 3G network. This actually drains your battery life very quickly as it's trying to scan for a 3G network belonging to your Telco constantly, among all the other signals that's broadcasting over the air.
   
   The EDGE network in Singapore is more predominant, and its even available underground. Disabling the 3G option will stop the constant scanning of signals, which in turn gives you better battery life.
   
   
3. Technically, the 3G technology promises a lot, but fall short on a few things. One of which is constant streaming of information from the 3G network while on the move.
   
   For example, if I'm in the MRT, its constantly moving from location to location. During its movement, your phone might have seemlessly switched between different base stations as the MRT is moving.
   
   The problem comes because you might be downloading something from one base station, but because you have moved out of range, the phone will connect to the next nearest base station. The telco's network would have to be smart enough to detect how much information has been downloaded to your phone, and re-route the rest of the information to the base station you're connected to now for you to continue the download.
   
   Now back to the iPhone 3G. Just by connecting to the normal phone network, the iPhone takes little battery power. The draining of the battery only comes when you're trying to receive data information. Therefore, the iPhone 3G only connects to the data network on a on-demand basis, to preserve battery life.
   
   So if you are currently now using Safari on the iPhone and downloading a very graphics intensive page, the iPhone would have to open a data connection and constantly probe this connection for data until it has finish downloading the page. If you're not on the move, its fine. But if you're on the move, the problem might come because the iPhone would be constantly trying to retrieve information from the base station because it does not detect that the download of data is completed. Sometimes when switching between base stations, the data download might be disrupted, and your Safari would be fruitlessly trying to retrieve information from the base station until Safari time-out, telling you that it is unable to connect to the network. This drains battery life, even if you're on the EDGE network!
   

For the reasons for turning the Wi-Fi/Buetooth off, its the same logic as turning off your Wi-Fi/Bluetooth when you're using your laptop. Without enabling your laptop's Wi-Fi/Bluetooth, the laptop battery lasts longer. Period. The explanation is roughly similar to the above.

Push notifications is something new to iPhone OS 3.0. What it essentially does is to have a small agent running in the background, constantly polling the applications servers for updates. This uses up less memory than having multiple applications open at the same time. However, this also means that the iPhone is working even though your application may not have anything to report. Personally, I disabled it because if I wish to be notified, I'll usually just open that particular application. The only notifications I need are SMSes and missed calls. Likewise, I've also disabled (switched to Manual) the Fetch New Data in Settings > Mail, Contacts, Calendars for the same reasons.

This is based on my own observations on how the iPhone might work. Therefore, I adjusted my usage to optimize the battery life. This is what I've done:

1. My iPhone 3G perpectually is always on EDGE signal as most of the time, I am on the move with the phone. Since EDGE signal almost covers the whole of Singapore (at least for Singtel) except for some rare blindspots, my iPhone will not have a problem connecting to a network.
   
   
2. The iPhone 3G is best suited for burst data, meaning grabbing of small amount of information at any point of time. Example would include using RSS reader, Google Maps, or reading of emails. Therefore when I am on the move, I usually only read RSS feeds (e.g. Bloomberg), or read my emails.
   
   Yes, for emails, its usually working on burst mode, which actually conforms with what the iPhone is meant to do. The retrieval of email headers in Mail is not data intensive, and can even be easily and quickly retrieved even on an EDGE network, although the 3G network will make the retrieval almost instantaneous.
   
   I will only switch to a 3G network or a Wi-FI network when I hang around a certain area, like an office or shopping mall. This I would do on an ad-hoc basis, if I need to surf around.
   
   I will always try to connect to a Wi-FI network first, followed by the 3G network. Reason is because Wi-FI actually uses less battery than the 3G network for some reason. With the availability of free hot-spots in Singapore, it has becomes a habit of mine to search for these hotspots when I need a fast connection.
   
   Before I make my move, I will switch back to EDGE network by turning off the Wi-FI or/and 3G network.
   
   
3. I will only connect to AppStore when I'm charging my iPhone 3G on my laptop. Downloading apps and updates from the AppStore could be quite battery draining so I will only do that when my iPhone is plugged in. Usually I will use Wi-Fi to download.
   

Things to note about the battery indicator on the iPhone:

1. When you charge the iPhone, take note that the battery indicator is charged to full. The first time I charge my iPhone, I've actually mistaken the iPhone to be fully charged, but in actual fact it is not.
   
   The green indicator should extend all the way to the end, with no gap inbetween the green indicator and the top of the battery. Refer to the image below on how the battery indicator will look like if its fully charged.
   
   
   
   It would be good if the next iPhone firmware patch will provide some sort of indicator if the battery is fully-charged. Refer to this post here on the iPhone 3G fully charged battery indicator. Less observant users will always be half-charging their iPhone, because I understand that the iPhone practises rapid charging, where the last 10% of the battery will charge slower.
   
   
2. The iPhone 3G will give off a warning if it falls below the 20% battery life indicator.
   
   
3. The iPhone 3G will give off a last warning if it falls below the 10% battery life indicator. This is the last warning indicator.
   

The last time I hit the 20% battery life indicator, the iPhone actually lasted me about 4+ hours more until I reached home. Yes, I was still using it during this time. :)

Hope this helps...