I've developed a simple circuit using a Photon to send data to my database. It has to be a portable device and because of this I looked into lead batteries. My circuit runs on 5V and draws a maximum of 1A per day. I need it to run for about 2-3 weeks, continuously.
When looking at lead batteries, I see a lot about nominal capacity. For example: with this battery the nominal capacity at 1Ah at around 5.25V gives a C20 value of 20A.
Can this information give me any kind of indication about how long the battery will last if I draw only 1A per day? In an ideal situation, if I only draw 1A per 20 hours, this would mean I could run my circuit for 20 times 20 hours so a little over two weeks. But I doubt this is an ideal situation. What does this C20 tell me about a longer usage of the battery, if anything?
Based on the information of my circuit, what kind of battery can you recommend? I'm aware I need a buck converter as well, which power dissipation I have not taken into account for my calculations yet.
Thanks for any insights you can give me.