Arduino 4S BMS: UPDATE (Version 5)

UPDATE:

This is an updated post regarding my 4S arduino based lithium ion balance management system (BMS).

If you click here, you will see the original post with details on the project.

IMPORTANT CHANGES:

1. Replaced external voltage reference to a more stable one. Upgraded to a REF3012AIDBZT from Texas instrument.  This does not require an output capacitor for stability.
2. Modified Buck converter RT6208GE.  Grounded pin 4 to set the max peak current to 50mA which is an average current of 25mA.  This was done to eliminate audible oscillation from the buck converter
3. Increased copper traces for ADC pins A0-A3
4. Better layout to increase continuous copper plane on internal layer

Minicore bootloader

updated 01/13/2019: For the new arduino version, load bootloader with 8MHz clock. I did more testing and this was more stable and accurate on the adc then the 1MHz clock setting.

I will be doing testing on these new versions and see how they perform.  I will post results as soon as I can.  Also below I will attach all files needed (schematics, gerber, bom) if you wish to make your own. 

Arduino Code Download

updated 01/13/2019: Download arduino code version A15.

Schematic and Gerber Download