Weather shield and red board

Hi, I purchased the red board and weather shield. I am new to the spark fun boards. There is a 3.3v and 5v switch. What does this do? I think this sets the entire system to 3.3v? What should this be set for using the weather shield?

I have two LFP batteries and solar cell. Solar panel output 12v to a two 3.2v cell LFP batteries on a cell balancing board. The batteries provide 6.4v 2S1P output. Looking at the schematic the barrel says 7v min. What’s the reason for this? How are others connecting batteries with solar charging to this red board and weather shield?

The switch sets the I/O voltage of the redboard’s GPIO pins

The Weather Shield is meant to use 5v I/O (‘logic’)https://learn.sparkfun.com/tutorials/ar … -guide-v12, so go ahead and set the switch to 5v https://learn.sparkfun.com/tutorials/re … e-overview (scroll a bit to see the section covering the switch)

Thanks!