Deep Monitoring – Analyzing Cell Health & Resistance


While SOC gives you a general “fuel gauge,” the JK‑BMS Deep Monitoring tools reveal the true health of your LiFePO4 cells. For AmpBox owners using 280Ah–314Ah cells, tracking Internal Resistance and Voltage Consistency is the best way to predict and prevent issues long before they become problems.

1. The Individual Cell Map

The main grid in the JK‑BMS App displays Cells 1–16 with real‑time voltage readings.

  • Color Coding: Highest cell is highlighted (Red/Orange), lowest cell (Blue/Green).
  • Delta (Δ): The voltage gap between the strongest and weakest cell.
    • Healthy Pack: Δ < 0.020V at rest.
    • Needs Attention: Δ > 0.100V near 100% charge.
2. Understanding Internal Resistance (mΩ)

Internal Resistance (measured in milliohms) indicates how easily a cell can deliver current. For large 280Ah–314Ah cells, consistency is more important than the exact number.

  • Low Resistance = Healthy Cell.
  • Uniformity Matters: All 16 cells should be similar.
    Example: If 15 cells are 0.25mΩ and one is 0.85mΩ, that cell or its connection needs inspection.
  • Loose Bolt Alert: Sudden spikes often indicate a loose busbar bolt or oxidized terminal, not a bad cell.
3. Monitoring Voltage “Sag” Under Load

A true health test happens under heavy load (e.g., running a microwave or heater).

  • Open the app while a large load is running.
  • Watch how each cell voltage drops.
  • If one cell sags significantly lower (e.g., 3.10V vs. others at 3.25V), that cell has higher resistance or is weaker.
4. Temperature Sensors (NTC)

The JK‑PB2A16S includes 4 internal temperature sensors to monitor both the BMS and the cells.

  • MOS Temp: Measures BMS transistor heat — normal to run higher during charging/balancing.
  • Cell Temp: Measures LiFePO4 block temperature.
  • Hot Spot Warning: A difference of 5°C–10°C between sensors may indicate a loose connection.
5. Cycle Count & Cumulative Capacity

The BMS logs every full discharge/charge cycle.

  • Cycle Count: One cycle = 100% of rated capacity moved (e.g., 314Ah).
  • Longevity: AmpBox cells are rated for 6,000+ cycles to 80% health — over 16 years at one cycle per day.

Healthy Battery Checklist:
• Delta stays below 0.030V at rest.
• Internal Resistances are nearly identical across all 16 cells.
• Temperatures remain within 3°C of each other.
• No active or historical alarms in the BMS log.

Deep monitoring ensures your AmpBox stays reliable, efficient, and long‑lived.

Back to blog