I thought I was working fine with 3.7v LiPo batteries but when I connected a super capacitor rather than a battery on for a bench test of something I noticed the charger pushed the cap to something like 4.3v.
So, am I overcharging a 3.7v LiPo?
In my environment I have a mix of 5v solar cells and 5v SuperCaps and what I think are 3.7v batteries.
I just realized now that I must be mixing them.
Batteries don't have a constant voltage, voltage decreases with the energie stocked inside... 3.7V is a medium value of your battery, which will be in reality between 3.2V when discharged (more or less depending of the protection for undervoltage) and 4.2V when full charged.
And a supercap is not a battery, it's possible than the constant current / constant voltage profil used for a battery could have some different result on a supercap, maybe not.
The PowerShield can take any battery up to 5V and boost it to ... 5V. The boost chip is LTC3525-5 - the SC70 package.
The design includes a MCP73831 LiPo charger and that naturally calls for LiPos to be used since they have good capacity and density and are popular.
LiPos during charging will read up to 5V actually, while USB power is connected (the charger goes through CV and CC cycles), that's normal. When fully charged the LiPo should read 4.2V or less.