I understand that typical alkaline batteries lose voltage as they die, making them a poor choice for sensitive electronics without proper handling, and that lithium AA batteries are usually slightly less than 1.5V per piece, so that it is very hard to get exactly 5V.
I would like to connect 6 alkaline batteries in serial for a total of 9V. This will decrease to around 5 volts as the batteries reach 20% of max capacity. To regulate the 9V from the batteries into usable voltage for the raspberry pi, I am considering this LM2596 power supply module, which purports to take an input voltage of up to 40V and output at 5V. Will this work for my intended purpose?
On a similar note, I am looking for some sort of battery that can power a raspberry pi at 5V/2A for about a week. I have a USB LiPo battery rated at 20,000mAh that works for about 24 hours. Does such a solution exist that is approximately the volume of a coffee mug or less? As an example, I have this battery laying around:
Sealed Lead Acid Battery 12V 9Ah and am wondering if this is compatible with the Pi using the same step down chip, and how long I might expect the Pi to last. Thanks for the info!