To my shock, chagrin, and horror, I have discovered a smartphone foible that has significant results for battery life.
My phone is a GSM phone. This, I am assured by wikipedia, means it is comfortable with 2G networks. Phone specs assure me it is also capable of connecting to 3G networks. In fact it is capable of connecting to HSDPA, sometimes called 3.5G. But whatever. The more common meaning of "3G" is WCDMA, which came before HSDPA. Still with me? I'm a bit lost myself on these topics, but lets forge ahead.
My phone allows me to choose network types, via: Menu > Settings > Wireless & networks > Mobile networks > Network preferences
And under Network preferences I get a list:
GSM/WCDMA (auto mode)
WCDMA only
GSM only
GSM/WCDMA (WCDMA preferred)
Where the phone says GSM it means 2G and where it says WCDMA it means 3G. (I think.) The default setting is the fourth, GSM/WCDMA (WCDMA preferred). In other words, choose either network but prefer WCDMA if you can get it. WCDMA is faster, and even a weak WCDMA signal can be better than a strong GSM signal. This fourth setting is presumably great if you have good 3G coverage in your area. But if you don't, then your phone will spend all day hunting for better connections. That is, while idle, it will still be working, sucking down battery juice, powering up the antenna to try and find some WCDMA connection.
So I've grown accustomed to charging my phone once a day. If I didn't, it'd flatten out within 24 hours. Battery percentage drops even when I'm not using it. I thought this is what smartphones do.
But as a test yesterday I set my phone to GSM only. It made no difference to the download speeds I get for my (minimal) data usage. It made a shocking difference to battery use though. Idling for most of the day, the battery strength dropped by, literally, 2 or 3 percent only. I would have expected maybe 20 or 30.
What does this all mean? My area has poor 3G? My China Mobile sim doesn't get 3G? The phone tells me I'm on an EDGE network which is not real 3G, more like 2.5G, but....
I dunno. I'm just blown away by how my phone isn't burning through the battery anymore doing nothing.