BatteryMind — 9V Internal Resistance Analyzer

About this project

BatteryMind is a precision 9V battery health analyzer that measures what your multimeter never shows you — internal resistance. Every 9V battery has a small internal resistor that grows as the battery ages. A fresh battery has 2–5Ω; a dead one has 50–100Ω. When your circuit draws 150mA, that dead battery's voltage collapses from 8.8V to 6V, causing Arduino resets and circuit failures. BatteryMind applies a calibrated 100Ω load via relay, measures the terminal voltage sag, and calculates internal resistance using Thévenin's theorem. Result displayed in 2 seconds: FRESH / GOOD / WEAK / DEAD — with LED color, a beep code, and exact voltage + resistance values on LCD.

What you get

• Complete, commented source code
• Full components list with quantities
• Pin-by-pin wiring guide and connection table
• Step-by-step upload and testing guide
• Project report (.docx, IEEE style)
• Presentation slides (.pptx)