Plans for version 2

• battery level indicator (LCD + DAC converter)
• 130 Ohm resistors for LEDs instead of 470 Ohm
• optional remote charger
• get power straight from PSU when in charge mode (something like TPS2113)
• add to power board logic level 3.3V
• brushless DC motors
• look into adjustable output regulator based on L78M and LS141
• choose an MCU. Forget about ATMega and RP2040, they don't have integrated battery management, that's why look into nRF52840
• LCD screen. What is refresh rate on LCD screen with SPI protocol?

Control voltage with microcontroller

Good ref: https://www.analog.com/en/technical-articles/digital-adjustment-of-dcdc-converter-output-voltage-in-portable-applications.html

Digitally Adjustable Boost Converter

Like TPS61045 or MAX686

Digipots and opamp

MCU controllable resistor - digital potentiometer (aka digipot)

Tweaking https://www.electronicdesign.com/technologies/analog/article/21801191/extend-lowvoltage-digipot-resolution-to-control-an-adjustable-regulator

FAQ https://www.analog.com/en/app-notes/an-1291.html

DAC

In general if you are not using a digital pot to handle an analog signal originating off-board, you don't need the digital pot, a DAC is the simplest approach. DACs are much more numerous and easy to source too.

MarkT

PWM

The high-frequency switching of the PWM output stage consumes much more power than a low-power DAC or digital trim pot, both of which are DC by nature.

Cascade of resistor dividers and mosfets Motorized potentiometer

LCD