My T-Mobile Dash Windows Mobile 6 Smartphone has a pretty decent battery. Up until recently it would generally have a 50 to 60% charge after being on for 12 hours or so (I turn it off at nights). My phone usage (voice and data) is pretty consistent on a day to day basis. Recently, however, it has been dipping down to the 30% range. One of my first clues was that the charge would be under 90% by the time I reached my office in the morning. So, what had changed on my phone in the past month or so? Gmail IMAP. I started using it on my phone when it became available at the end of October. Gmail’s IMAP4 server is incredibly slow. You can see how slow it is on a desktop mail client if you use other IMAP4 services. The web hosting service for MobileViews.com, for example, provides IMAP4 mail service too. It works pretty quickly with Thunderbird in terms of updating the mail list and opening mail to read. Google’s IMAP4, in contrast, is glacial. It takes forever to update a list or open a single piece of email. So, I changed WiMo’s messaging settings from checking Gmail once an hour to once every four hours. I manually had messaging check gmail about once or twice in between. So, mail was checked about once every 2 hours instead of once an hour: A 50% reduction for that event. My battery life improved a bit after that. It moved up to between 40 an 45%. I changed Gmail’s messaging setting so it only auto-checks the Gmail IMAP4 server once a day. Over the past couple of days, my battery charge at the end of day has been between 55 and 65%. Much better. I should probably set WiMo messaging to check Gmail several times a day again and confirm that this is what caused the battery drain I saw.