gemsworld wrote:
For aesthetics reasons, I'm hoping a motorcycle or UPS backup battery will work so I can house all the necessary components in a small weather-resistant enclosure near the webcam.
Either will work, but neither are really the best for the job and may not have a long life. I don't know of any SMALL true deep discharge lead acid batteries.
Li-Ion is a possibility, but it will run your cost up ! First, you will need a charge controller that will handle Li-Ion batteries. Then you need the batteries themselves. Li-Ion batteries have a nominal 3.7V but must be charged at above 4.0V. so 4 Li-Ion batteries in series will need to be charged at more than 16.0 Your inverter might not like that. Adding 3 diodes in series between the positive of the battery pack will get you to about the proper voltage.
You will likely need 3 or 4 four battery packs, wired in parallel. Expensive, but they will last a very long time.