ron_sutherland:
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Looking at LiFePO some and found something I did not think about, which is that current stops flowing through a LiFePO cell after it is charged and kept at 4.2V, this is not true with lead acid since the cell will let current flow during equalizing. The shunt should work with LiFePO also, and now I am wanting to change my solar charge controller to use LiFePO.
I have the same conclusion,
They are cheaper/easier to charge.
Need two cells for arduino though.
LiFePO cells have a better temp/capacity curve at low temperatures as well.
Overnight with no sun that can make a big difference here.