Connect to the battery screen like standard. Then it will read voltage and throw out a battery percentage!
Can you share more details about the build. I have a V3S and i have 2 more batteries, so my goal is to do what you did, but have 2 batteries on top, between feet. I want to know how do you connect it, because i heard that if your mounted battery is discharged, it can cause problems when you connect fully to charge battery. so what type of circuit did you do?