So my configuration is like this 2x 3.7 2200 mAh batteries in series doing 7.4 V in total --> Lithium Battery Charge module (its connected to a solar panel and yes the output its 7.4 V from it)--> Step Up Buck that takes the 7.4 V to exactly 11.7 V --> motor driver L9110s ---> Arduino Nano which also has a HC-05 connected to the 5 V of the Arduino Nano and I suspect there is a drop in voltage that makes the arduino reset itself when I start up the motors. Arduino Nano works fine like all the modules on it while on VIN and Bluetooth but when I start the motors it resets itself. What should I do to fix this issue ? Thanks ! (also sorry for not posting a schematic but only through text cause its morning and I am really tired and I am not on my home computer)
Firstly you should measure total energy cost of your system. Then measure your energy production from your solar panels and multiply it the efficieny of your buck converter. Seperate VIN and motor cables, use diodes for both of them. After diodes for VIN side, add some capacitors(tantalum is better). Observe the VIN side with an oscilloscop for Voltage drop.