I recently bought this GSM adapter:http://www.ebay.co.uk/itm/130822162881?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
I am also trying to conserve power, but have a different use-case as I need to listen for commands from SMS messages. Which means I am likely to have to periodically wake up and check for SMS messages and then go back to sleep again.
Last night I was trying to get a feel for power consumption of the board. It needs its own 12v supply in order to run it's large onboard voltage regulator 4v I think. I think they just say 12v to be safe, but I think you'd get away with anything above about 6v provided it could supply enough current. I am working in a 12v environment (12v lead acid batteries and solar panels) so 12v is fine for my case.
I'm using a Xino Basic board, which is pretty bare bones. It has its own 5v and 3.3v regulators installed on it.
I was using a simple digital multimeter to read the current usage. Not that accurate or fast, but enough to give some kind of idea.
When the board powers up it seems to use around 1A for a short while, then settles down to running at about 70mA. That is the GSM shield and the Xino Basic together, fed via a 12v supply (with the Xino's 5v regulator feeding the Xino, and the GSM regulator feeding the GSM board), and connected to the GSM network (ie. listening). That was surprisingly low, I was expecting it to be much higher. I think I measured the Xino Basic on its own at using about 30mA. That is with no power saving techniques, the 5v and 3.3v onboard regulators running and the power LED on.
When an incoming SMS message arrives the current jumps up to around 150mA - 200mA briefly, then goes back down to 70mA. I couldn't get it to send an SMS last night for some reason (it was working previously). I think I may have run out of credit and need to top the account up.
I am thinking about switching the Vin to the GSM shield via a MOSFET on the Xino, so that I can power it up and down via software. I just need to make sure that the power saved whilst off isn't negated by the extra power required at the start to find and join the GSM network every time I wake up.
I have attempted to switch the GMS radios on and off via AT commands, but that didn't seem to do anything (the GSM network led still blinked as though it was connected to the GSM network).