The next step is to evaluate the best way to interface an ATtiny85 to monitor and control the circuit.
Saturday, April 25, 2015
HP-0014B PRO Charge Controller Circuit Diagram
I spent some time mapping the Li-Ion charging circuit I purchased. As far as I can tell the circuit is a combination of the reference design for each of the integrated circuits - U2, U3, and U4 - and an RC filter. My guess is that the RC filter is supposed to keep the noise from the DC/DC converter from interfering with the current monitoring of the lithium cell charging IC.