Hi,
I am working in a project which consist of:
-STM32 arm microcontroller (It has Volt-Reg on board, so Can be powered with any voltage >3.3V)
-GSM module (Require 5V with high current)
-Pressure sesnsor (Require any constant voltage in range 3.3v~5v)

I plan to make a pressure logging system which will work ~1 year with a single battery charge as it sleeps for long period and run short time to collect data then send through gsm communication

So it have to use a most power efficient method to power this project

I can't find a 5v battery, So I working with 2 lith-ion batteries of 3.7v~4.2v each

Now I have to scenarios:
1-Connecting two 3.7v batteries in parallel to get a 3.7V then use a step-up converter to get a 5V battery
2-Connecting two 3.7v batteries in series to get a 7.4V then use a voltage regulator to get a 5v.

Which is the most power effictive way to not wast a lot of power?


Thank you
And sorry for bad english

 

In general a step-down buck converter is more efficient than a boost converter, so I would go with that with the batteries in series.

 

I would start by finding another GSM module, one for direct supply from a single lithium cell.