I am creating project where I want to reduce the number of required parts + power consumption to minimum. First I wanted to use atmega328p on 1MHz. I was planning to power it with 3 x AA NiMH batteries which means 3.9V when fully charged. I planned to use a schottky diod to low down the voltage which should be then at 3.5V when fully charged batteries. I would like to use that project in connection with Sigfox and NRF24l01. Both are able to work under 3.3V same as the atmega328p. I wanted to remove the voltage regulator completely if possible. Do you think that this is a good way how to power the devices? The voltage should be then from 3.5V when batteries fully charged to 2.7V when discharged.
Later on I may switch to 8MHz atmega328p as it can happen that the software serial communication will be not sufficient with the Sigfox module. But according to datasheet even on the 8MHz should be ok with the voltage of 2.7V. In the future I also wanted to charge the NiMH batteries by the small solar panel to let operate the devices for longer time. Anyway I am using the power down mode of all devices and powering them only for about 1/8 of time. When the solar panel would be used, is it better option to use for example just one NiMH battery with step-up regulator and small solar cell connected with diode directly to the battery? I would use for example a 2V solar cell + diod + 1 NiMH battery and then step-up voltage regulator to go to 3.3V.
Any advice and help will be appreciated.