Straight from here
http://support.microsoft.com/kb/927710/en-us?sd=zune(but I know some people are just lazy or don't want to look)
How to help maximize the time that a battery lasts in your Zune device
To help achieve maximum battery performance, follow all these guidelines:
• Update the firmware on your Zune device. For more information about how to update the firmware on a Zune device, click the following article number to view the article in the Microsoft Knowledge Base:
926770 (
http://support.microsoft.com/kb/926770/) How to update the firmware for your Zune device
• Reset the Zune device. To reset the Zune device, set the Hold switch to the unlocked position, and then press and hold the Back button Back button as you press on the top of the Control Pad. When the device begins to reset, you can release the buttons.
This step helps make that sure the Zune device is reliably operating. For example, after repeated use, the Zune device may incorrectly report that it is charging by displaying an animated battery icon, even though the device is not connected to a power source. Resetting the device will correct this. Resetting helps conserve power.
• Use the Zune device at room temperature. The Zune device operates most efficiently at room temperature.
• Use the "Play all" option or the "Shuffle all" option. The less that you interact with the Zune device, the longer the battery will last. When you play music, try to use custom playlists. Additionally, try to use the songs, genres, albums, or artists views together with the Play all option or the Shuffle all option.
For more information about how to create playlists, see the appropriate topic in Zune Help. To do this, follow these steps:
1. Open Zune Software, and then press F1.
2. On the Contents tab, expand Organizing your music, and then click Using playlists.
• Use the Hold switch. By using the Hold switch, you can help prevent unintentional activation of the Zune device. The Hold switch is located on the top of the Zune device. Set the Hold switch to the locked position when you do not want to interact with the Zune device. For example, you may want to set the Hold switch to the locked position when the Zune device is in a traveling pouch or in your pocket.
• Play Windows Media Audio (WMA) audio files. You experience the best battery performance when you play WMA music at 128Kbps. For the most efficient use of the battery, try to use WMA files at 128Kbps to sync, to store, and to play your music on your Zune device.
To adjust the quality of music that syncs with your Zune device, follow these steps:
1. Start Zune Software, and then connect the Zune device by using the Zune sync cable.
2. After your Zune device connects to Zune Software, click Options, point to Sync, point to your Zune device name, and then click Advanced Options.
Note In this step, your Zune device name represents the actual name of the Zune device.
3. Click the Quality tab.
4. Under Music, click Select maximum quality level, and then move the slider to the appropriate quality level.
5. Click OK.
• Turn off your Zune device. To turn off the Zune device, press and hold the Play/Pause button Play/Pause button until the Zune device turns off. When you turn off the Zune device, the Zune device remains in low-power standby. Typically, the Zune device resumes operation approximately one second after you press one of the buttons. The Zune device also automatically turns off after 10 minutes of inactivity.
If you do not start the Zune device within approximately 24 hours, the Zune device enters sleep mode. Although we recommend that you let the Zune device enter sleep mode automatically, you can put the Zune device to sleep manually. To put the Zune device into sleep mode manually, press and hold the Back button Back button as you press down on the Control Pad. When the Zune device is in sleep mode, the Zune device resumes operation after you press the Play/Pause button Play/Pause button. In this case, the Zune device requires approximately 13 seconds to restart.
• Adjust the backlight. You can set the backlight to the following display times:
• 1 second
• 5 seconds
• 15 seconds
• 30 seconds
• Always on
For the most efficient use of the battery, select the shortest display time that works for you. To change the backlight setting, follow these steps:
1. On the Home screen, select Settings, and then press the OK button in the center of the Control Pad.
2. Select Display, and then press the OK button.
3. Select Backlight, and then press the OK button to toggle through the settings.
• Adjust the brightness. You can set the brightness to the following display levels:
• Low
• Medium
• High
For the most efficient use of the battery, select the lowest brightness level that works for you. To change the brightness setting, follow these steps:
1. On the Home screen, select Settings, and then press the OK button.
2. Select Display, and then press the OK button.
3. Select Brightness, and then press the OK button to toggle through the settings.
• Turn off the radio when it is not being used. When you are finished listening to the radio, it may be necessary to turn it off. The radio automatically turns off when you play music, view a picture, or play a slide show. Pressing the play/pause button or unplugging the earphones mutes the sound from the radio, but the radio remains on. To turn off the radio, briefly play music, view a picture, or play a slide show or video.
• Remove back-to-back songs in your playlist. If the same song appears consecutively two or more times on your playlist/quicklist, the device may have to frequently access the hard drive. To limit excess hard drive accessing, avoid adding the same song more than one time, or at least avoid having the same song appear consecutively.
• Adjust the Wireless setting. The Wireless setting alone has little effect on the time that a battery charge lasts. To share files and to experience the social environment that Zune offers, we recommend that you keep the Wireless setting turned on. However, you can turn off the Wireless setting to preserve a small amount of battery power. To change the Wireless setting, follow these steps:
1. On the Home screen, select Settings, and then press the OK button.
2. Select Wireless, and then press the OK button to toggle between On and Off.
The amount of files that you send or receive has a significant effect on the time that a battery charge lasts. If you send or receive many files, you may have to charge your Zune device more frequently.