I’m looking to deploy XBee modules, reading one input, waking every 30 minutes to transmit status. What sort of batteries are others using in this application. 3.0V lithium or 2 x 1.5V alkaline seem appropriate. That way I can eliminate the need for a voltage regulator.
However I see the Digi adaptors use 3.6V lithium batteries. Why is that and how do they drop the voltage to the maximum 3.4V supply of the XBee module? They need to do this very efficiently, without wasting energy?
The Digi adapters do use a voltage regulator. For the battery they also use a 3.6V lithium and fairly large capacitor.
Batteries which are rated close to the lower end of the operational voltage of the module may not be the best choice in the long run in any case. First, as the batteries get older they will lose some of their voltage. Second, when the device transmits and draws a large amount of current, the battery voltage will drop. Dropping battery voltage more than about 100mV could cause transmission problems. Thus the need for a solid capacitor.
You say the adaptors use a voltage regulator. What sort? The XBee modules have an upper voltage supply of 3.4V, If the battery is 3.6V, what sort of regulator are they using with such low drop out?
What do you call a large capacitor? I was thinking of 100uF at least.