I've never designed a battery pack for a device before so please be patient with me if this sounds trivial. The task is to build a battery pack for a device that runs off 12V, draws 1-10 mA (which I measured using a .1-ohm sense resistor while it was operating), and must run for 4~5 hours.
The device is a radio transmitter. I don't have its internal schematics but know that it runs off of 12V fed through a DB25 RS232 connector.
I read this article (1.5V vs 9V) which concluded that 1.5V batteries have higher energy density than 9V batteries. This article (the capacity of 1.5V batteries) suggests that capacity vary with current draw.
With those two articles in mind, I thought of two solutions:
Option 1 is to get 12V from eight 1.5V batteries. Hooked up in series.
Option 2 I had in mind was to go with (2) 9V batteries (in series) with a voltage divider to get the 12V. The additional resistor means wasted energy but I don't care about efficiency -- the device only needs to run for a demo for a couple of hours.
I don't think I have to take load-distribution into account (because this is a quick one-off project and not part of a device to be mass-produced). Are there other things to consider?