brhyaa729:
I think I have the answer to my own question, I could use two 9 volt batteries in parallel to double the life and remain at 9 volts without adding much bulk to the project.
Have you priced what 9 volt batteries retail for? They are a very poor choice both from a capacity and cost point of view. Either convert to series alkaline AA batteries for use a DC power module. 9 volt batteries are for smoke alarms.
Lefty