Does your iPhone suffer from the low battery blues at the end of a busy day? Here are five fast ways to keep the iPhone's battery alive for a bit longer. They're especially handy when you're travelling overseas and don't have chargers dotted around you in convenient places.

1) Disable Bluetooth and Wi-Fi

If you're not using a Bluetooth headset or connecting your phone to a Wi-Fi hotspot (or your jerry-rigged hotel room Wi-Fi internet connection), you should disable Bluetooth and WiFi on your phone as a power saving measure.

First, go to settings in the iPhone's main menu:

Then select the Wi-Fi menu...

Tap the Wi-Fi slider to switch it to "off".

Once you've done that, you can either click the "settings" link at the top of the screen to go back to the top page of settings. Then tap on "general"

Now, select the Bluetooth menu.

Tap the Bluetooth slider to turn Bluetooth off.

Now, your Wi-Fi and Bluetooth should be disabled, which will save you power when you're out and about. You can re-enable them using the same process.

2) Disable 3G

This is the big power-saving tip: 3G sucks a lot more power than the old 2G/GSM telephony. Most 3G phones (including the iPhone) can be switched back to using 2G, and you'll still be able to make voice calls and receive email as normal.

Web browsing is, of course, slow on 2G, but you you can always turn 3G back on when you need it (as a side issue, slow data can be a good thing when you're paying global roaming charges anyway, since the faster the internet, the faster you will burn through megabytes at $10-$20 per megabyte at global roaming rates -- and of course, you're best off disabling data altogether when roaming and only using Wi-Fi hotspots).

In the main iPhone home screen, tap on the settings icon.

Then select the "general" menu.

Now, tap the "network" menu.

Tap on the "Enable 3G" slider to turn off 3G.

Now, your iPhone will only use 2G networks, which are just as good as 3G networks for voice calls. The exception is in Japan, where you need to have 3G enabled to connect to the mobile network at all.

You can re-enable 3G by following the same steps.

3) Turn down screen brightness

Another big power sapper on smartphones is their big, bright screens. Turning down the brightness from full to half often makes very little difference in legibility but can contribute to considerably longer battery life.

In the main iPhone home screen, tap on the settings icon.

From the settings menu, tap "brightness".

Use the slider to adjust screen brightness to the minimum level you can tolerate.

You can turn your screen brightness up at any time by following the same steps, but keeping brightness turned down saves a lot of battery life.

4) Turn off push email and services

"Push" technology -- where email and notifications are sent to your phone instantly rather than your phone retrieving them on a timed schedule -- saps your battery, because the phone has to keep a live connection to the net at all times.

In the main iPhone home screen, tap on the settings icon.

Tap on the "Mail, Contacts, Calendars" menu option.

Select the "Fetch new data" menu option.

Tap on the "Push" slider to turn push email/notifications off. Also, under the "Fetch" section, we suggest selecting the "Manually" option, which means the phone will only download for email when you actually open the email app and check for email. This will save battery life and minimise data charges, because you can check email when you are connected to a Wi-Fi hotspot.

You can easily re-enable push and/or change the frequency that the phone will fetch new email on a timed schedule by following the same steps.

5) Consider a beefed up battery-pack

If you still don't get the battery life you need with all of the above tweaks applied, you might consider getting a third party battery pack to top your phone up.

For iPhone, there are two main types:

• 

  ones that are separate to the phone and feed juice in only when you connect it to the iPhone dock connector. The upside of these is that you can use them to charge other devices, such as your iPad or iPod. Examples: Energizer Energi to Go XP4001 two-USB port battery pack ($99), Kensington Mini Battery Pack for iPhone and iPod ($49.95), Mophie Juice Pack Powerstation ($129.95).

• 

  ones that are built in to protective cases and wrap around the iPhone, constantly giving it extra juice. You recharge the iPhone and battery case together, at the same time, using a charging cord that attaches to the battery case. The advantage of these is that they effectively give you a permanent upgrade to your iPhone battery life. Examples: Energizer Energi to Go iPhone 4 case ($89.95), Energizer Energi to Go iPhone 3G(S) case ($99.95), Padacs Powercase for iPhone 4 ($49.95) and Mophie Juice Pack Air ($89.95).