Sprint HTC Hero :: Wi-fi Battery Saving Method

I stumbled upon a new wi-fi setting yesterday that is fairly hidden and not mentioned in the manual at all, so I though I'd share it here.

First, a little background and explanation, then I will share my new findings with you all. It has been confirmed in other threads that the wi-fi radio uses considerably less power than the EV-DO 3G radio in the Hero. When you think about it, it's actually pretty simple because the signal only has to travel 100 or so feet for wi-fi, vs. several miles for the 3G radio. Whenever I'm at home or anywhere else with wi-fi, I always switch the wi-fi radio on, and have found that the battery lasts much longer. Whenever the phone is awake, and you're actively connected to a wi-fi network, it seems to shut the EV-DO radio down completely and rely solely on the wi-fi data for data. This has been confirmed as true, because there are some programs out there (i.e. Sprint TV) where you have to turn wi-fi off, because they will only access with the EV-DO radio. You obviously want to turn the wi-fi off whenever there are no networks around, because it will actively search for networks whenever it is on, and will run the battery down.

So, I noticed every time I would wake my phone up after I hadn't used it for a while, it would be using the EV-DO radio, and would take a few seconds to re-connect to my wi-fi network. I couldn't quite figure out why the phone would revert back to EV-DO when sleeping, then connect back to wi-fi only after waking the phone back up. Yesterday, I stumbled upon a new menu I hadn't seen before where you can change this behavior. Check this out.

Menu->Settings->Wireless Controls->Wi-Fi Settings->Press Menu Again->Advanced->Wi-Fi Sleep Policy

The description for this menu reads "Specify when to switch from Wi-Fi to mobile data."

Within this menu, there are three options.

"When screen turns off."
"Never when plugged in."
"Never."

The default setting is "When screen turns off." So, even with wi-fi enabled, whenever the screen turns off, your phone automatically reverts back to the EV-DO radio. As we all know, your phone is still transmitting data a good portion of the time, even when you're not using it. So, even with wi-fi turned on, the phone is still using the 3G radio to communicate while the screen is off.

I switched this menu setting to "Never" as of last night. This forces the phone to always use wi-fi whenever it is turned on, and you are connected to a network. Since then, whenever I wake up my phone it is still showing the wi-fi icon, and I haven't seen the EV-DO icon at all like I used to see for the first several seconds.

I was at home most of the day today, connected to my wi-fi network. I left the house twice for probably about 2 hours total, and I switched off wi-fi both times I left the house. I used the phone fairly lightly today, since we had a family day, but that still consisted of a good bit of browsing, some email usage, light texting, reading twitter updates every two hours, and half an hour playing a video game. Also, I always leave my GPS switched on as it never activates unless I open a program that requires it, and it always switches back off after I'm done. I took the phone off the charger at 9:30 this morning, and it is now 11:50 pm as I'm typing this. So, we're looking at over 14 hours today. The phone hasn't touched a charger since this morning, and I am sitting at 52% battery life, and I'm about to plug the phone in and go to bed.

I have never seen anywhere near this kind of battery life at the end of the day. I am usually below 15% after this kind of usage. I'm not sure if this was just a freak day, or what, but I really believe changing this one setting had a profound affect (effect?) on my battery life.