USB - Solar - LiPo charger decrease output voltage

[simon.t]

Hi guys,
thanks for the nice design+tutorial of the charger. I understood how to adjust the max charge current.
My question:
How do I control the LOAD voltage? e.g. if I'd need 3,7V instead of 5V.

[adafruit_support_bill]

To limit the load voltage, you would need an external regulator.

[simon.t]

thanks! the idea is to reduce the power consumtpion the device connect to load uses (from 0,5W at 5v to about 0,45W).
will an external regulator (i assume you mean something like a linear regulator or a buck converter) make sense or will the potential gains be lost in the inefficiency of conversion?

[adafruit_support_bill]

A linear regulator won't save you anything. (All your savings will be dissipated as heat) Buck converters are typically better than 90% efficient. We have 3.3v buck converters in the store. http://www.adafruit.com/products/1066

If you need precisely 3.7v, Dimension Engineering makes a nice adjustable voltage converter.