I am looking for a prebuilt low power wake-up module to power up a regular Arduino Uno R3 which is also run from a battery.
I'd like it to run on low power and wake up every minute or so and check the voltage of the main Arduino battery. It would also wake up the main Arduino when necessary. The main Arduino would then do necessary alarms etc.
My question is this: Are there ready made module (pretty much similar to above project) I coul buy from aliexpress etc.? I do not want to re-invent the wheel.
Why not build that device, and connect pin 7 to an external interrupt pin. When the LP device sets pin 7 HIGH (or LOW), it can wake the Arduino up. The LP device obviously wouldn't leave pin 7 HIGH for longer than necessary to wake up the Arduino.
You can get the 3.3 V version Pro Mini with the ATmega328P chip do some modification to disable Power LED and voltage regulator then program it and you have the Low Power Device.
I have not seen any ready made low power module as the demand was very low I guess, most have build it with own ATmega328P chip project.
I'd like it to run on low power and wake up every minute or so and check the voltage of the main Arduino battery. It would also wake up the main Arduino when necessary.
Your not making much sense -
when would it be necessary to wake up the Arduino?
Why wake the Arduino to check it's battery? And even more why every minute
If you can't say what condition need to wake the arduino who can any one tell you what to use to wake up the Arduino?
If you want low power then don't use an Uno. Just build an Atmega 328 on piece of stripboard. It will have all the functionality and it will have very very low power consumption in sleep mode - probably no more than the Attiny.
@billhowl gave you a link to Nick Gammon's very useful power saving tutorial.