MAX77751CEFG+ Battery Charge IC. Fairly smart chip, and takes USB lines as an input, simplifying single-cell charging.
Today, I am beginning to finalize the firmware for the V3.0.0-A design, and put together, then cleaned up most of the schematic level design elements for the extension board in the previous log.
Above being the USB interfacing battery charger, and below being the switching regulator with a controlled enable (the bridge to VBUS will change) so that detection of the USB VBUS lines by the RP2040 can indicate to the power system of the extender to switch from discharge to charge/topoff mode.
I might add a second log today if I finish the firmware early.