I am a software engineer, but new to hardware hacking, so I apologize if this is missing any detail, I will try to be thorough and update with any requested information. I also tried to keep this as specific to the topic as I could.
I am working on a small tracking system as a personal project. I am using a SparkFun Pro Micro board based on the RP2040 that I had laying around as a microcontroller, and I want to use the SparkFun Ublox NEO-M9N as the GPS unit. I had a spare ceramic antenna that I attached to the GPS unit's antenna socket. For the software side I installed MicroPython on the MC board.
I have the system working, but now I have to think about how to get as much battery life out of this as I can. My requirement is to get 7 days of life out of the device between charges. It looks like at full throttle the system needs ~180mA. I am also somewhat constrained in that this tracker must be 0.25" thick or less.
The thickness requirement ruled out a lot of connectors and cable based solutions like a LiPo. I can build outward using up to a standard letter sized envelope in surface area, but the depth is a hard requirement. My plan is to solder power or a female port to the board/use, or a small USB-C cable to use the Pro Micro USB-C port.
As for getting the most out of whatever power solution works best:
My natural inclination is to introduce waits and deep sleeps through MicroPython, configure the GPS board to poll less frequently, and other software based efficiencies. I don't want to spend a lot of time optimizing something with little effect on the power issue, however, and worry I overestimate the role of software in getting power supply right. (If all the software optimization is equal to cutting off the LEDs I should skip the code at first)
I have come across some people talking about voltage converters and such to decrease the power waste, but I am struggling to find a good primer on how to think about power consumption and supply.
I know very skilled electrical engineers can make hearing aids that last weeks on coin-cell batteries, but I have a hunch I can get done what I want without such sophistication.
Finally: I have a 2500 mAh battery that supplies 3.3V, if I connected that to the board it should last (in theory - disregarding wear on the battery) 2500/180 ~ 14 hours, correct?
Is the best way to do this to just use a multimeter and go from that benchmark?