Arduino pro mini 3.3V + solar panel - one 18650 3.7V or three 1.2V AA batteries?
I am planning on building a simple weather station which is going to have an outside unit (sender) and a receiver inside.
In the outside unit I would like to use a 3.3V Pro Mini. I also have a 6V 100mAh solar panel laying around, I know it is not much, but I want to install it somewhere. I also have a bunch of 1.2V AA Ni-Mh batteries, with around 7-800 mAh capacity, and some TP4056 18650 charger unit with protection circuits.
The question is which method should I use:
a) Hook three AA batteries in serial and connect the solar panel directly to them, with a diode of course.
b) Or would it be better to buy a 18650 Li-Ion cell and connect it to the solar panel with a TP4056?
I also want to program the Arduino to put itself in some sort of sleep or power saving mode, and just wake up in every 2-3 minutes to measure and send data. Any suggestions or experiences about this? Is the built in LowPowerDeepSleep mode would be enough?
This may not be applicable to your questions but as you are in the planning stage I show a link to a project on indestructible that may be of interest. I actually got all the parts a while back but too many other things to do.. but a satisfyingly larger parts bin I suppose. ?
I hope you let us know about the progress of your project.
There is a lot to be said for keeping it simple in the early project stages. If you already have the Ni-Mh and you aren't sure what your current consumption will be then the Ni-Mh would be an easy way to get to the next stage of the project without distracting you from the goal. Just leave room in your station housing for bigger batteries.
I know this is late but take a look at the Adafruit Low Power Library.
Maybe you can make use of it!