Writing a Python Script to Track Solar Battery Health

Author: Marcial Rey (In Between Bamboos Farm)

LiFePO4 (Lithium Iron Phosphate) batteries are the gold standard for off-grid farming, powering my incubators and pond aerators. However, knowing exactly how much juice is left in them is notoriously difficult because their voltage curve is incredibly flat. A battery at 70% charge looks almost identical in voltage to a battery at 40%.

To monitor my true capacity without buying an expensive smart-shunt, I wrote a Python script that takes raw voltage readings and calculates the estimated State of Charge (SoC) based on the specific chemistry of LiFePO4 cells.

The Code: The Python SoC Calculator

This Python script accepts a voltage reading, matches it against the standard 12V LiFePO4 discharge curve, and prints out the true battery health.

# battery_health_monitor.py

def calculate_lifepo4_soc(voltage):
    """Estimates State of Charge (SoC) for a 12V LiFePO4 battery"""
    if voltage >= 13.6:
        return "100% (Fully Charged)"
    elif voltage >= 13.3:
        return "90% (Excellent)"
    elif voltage >= 13.2:
        return "70% (Good)"
    elif voltage >= 13.1:
        return "40% (Monitor Slowly)"
    elif voltage >= 12.8:
        return "20% (Prepare to Recharge)"
    elif voltage <= 12.0:
        return "0% (Critically Depleted)"
    else:
        return "Calculating..."

# Simulated reading from a battery sensor at the pond
current_voltage = 13.15

soc_status = calculate_lifepo4_soc(current_voltage)
print(f"Farm Battery Status: {current_voltage}V")
print(f"Estimated Capacity: {soc_status}")