I'm thinking about making an app which will require Bluetooth to be available at all times. However, if this reduces battery charge life significantly, then that's kind of a show stopper. Can anyone give me a general idea about how much drain constant Bluetooth use will put on the battery?
What drains... my special. Here some data samples, based on a Motorola Droid:
+--------------------+----------+ | Mode | Energy | +--------------------+----------+ | Bluetooth receive | 751 mW | | Bluetooth send | 487 mW | | Bluetooth standby | 2,8 mW | +--------------------+----------+
So if you use BT quite regularly (e.g. to be able to immediately pick up a call with your headset), having it in standby doesn't hurt that much (Compare: 2G StandBy 11,6 mW, 3G StandBy 18,3 mW, Wifi StandBy 7,8 mW -- and, often mistaken: GPS StandBy 0,4 mW).
But if, on the other hand, you use BT once a week (or even less) -- heck, you can manually enable it then, there are enough "toggle switches" and widgets available.
It really depends on what you are using Bluetooth for. I have a Bluetooth watch (MBW-150) that I sync with my phone using OpenWatch and it affects my battery life minimally. All it does is sync the phone's time with my watch, vibrates on certain notifications/calls, and gives me control of my music player (play/stop/next/prev/volume). So I essentially have Bluetooth turned on all the time and haven't really seen a battery problem because of it.
I have a Samsung Galaxy S (Vibrant):
With Bluetooth & Sync turned on, but the Bluetooth not connected, I better have > 45% battery before I go to bed or else my phone will be dead by morning.
With Bluetooth & Sync turned off, I only use 1-2% battery overnight.
How much of that is Bluetooth and how much is Sync, I don't know. But the combination sure kicks the crap outta my phone.
Personally i recently got a wireless earphones for making calls and sometimes i turn my earphones off but forget to turn off my bluetooth on my phone. I usually found this to be a problem since i would charge my phone before gping to bed and leaving it at 50%. Before it used to last me over night but lately i been waking up to zero percent battery... so personally i don't advice you to leave bluetooth on... plus for me it cause my phone to overheat while charging.
Below is an article from Techrepublic. There is a lot of anecdotal "yes" here, but very little scientific responses. I think if you look at the actual analysis responses using hard data, you'll see that bluetooth has little impact on battery. I never turn off bluetooth on my phone and have several apps that use bluetooth, and the only time my battery doesn't last all day is when I play a game or two on it.