This project presents a DC battery monitoring setup using the Peacefair PZEM-037 Battery Coulomb Meter. The PZEM-037 is connected directly to a battery and measures four key electrical parameters in real time: voltage, current, accumulated capacity (Ah), and remaining battery percentage. All readings are displayed on the module's built-in LCD screen.

This setup requires no additional hardware beyond the PZEM-037 module, a 100A pure copper shunt, a USB-USB male-to-male cable, and the battery under test. The module handles all measurement and display functions internally, making it a straightforward and reliable solution for battery health monitoring and energy logging in DC systems ranging from 8V to 100V.

This project documents the hardware connections, display readings, and correct operating procedure for the PZEM-037 to help others set up and use the module accurately for battery testing and monitoring applications.

The PZEM-037 battery monitoring setup is suited for any application where DC battery performance needs to be measured and tracked without a complex control system. Key use cases include:

• Battery Health Monitoring — Connects directly to a Lead-acid or Li-ion battery to display real-time voltage, current draw, accumulated capacity (Ah), and remaining capacity percentage, giving a clear picture of the battery's current condition.
• Battery Capacity Testing — Measures how much energy a battery delivers during a discharge cycle by tracking accumulated energy (Ah), allowing users to verify the actual capacity against the battery's rated specification.
• Load Testing — Monitors current draw and accumulated capacity (Ah) from a connected load during operation, useful for checking whether a battery can sustain a device's current requirements over time.
• Learning and Development — Serves as a practical hands-on introduction to DC electrical measurement concepts including voltage, current, capacity, and charge, making it suitable for students and hobbyists learning about battery systems and electronics.

Gather everything below before you start. This is your checklist — names, models, and versions only.

Here is what each component does and why it is part of this project.

The PZEM-037 is used for real-time monitoring of battery voltage, current, capacity, and remaining battery percentage. It is commonly applied in battery management, solar energy systems, backup power systems, and battery testing to help users monitor battery performance and prevent over-discharge.

The 100A shunt is used to accurately measure the current flowing through a battery or DC load. It is widely applied in battery monitoring systems, power distribution systems, and electrical testing where precise current measurement is required. As current flows through the shunt, a small voltage drop is produced across its terminals, which the PZEM-037 measures and converts into an accurate current reading. Using pure copper ensures minimal resistance change with temperature, which is important for accurate measurements during extended testing sessions.

The USB-USB male-to-male cable serves as the communication link between the shunt and the PZEM-037 display module. It enables the transfer of measurement data from the shunt to the display, ensuring that real-time voltage and current readings are shown correctly. No separate signal wiring is required for this connection.

Lead-acid and lithium-ion batteries are widely used as energy storage devices in applications such as solar power systems, electric vehicles, backup power supplies (UPS), portable electronics, and industrial equipment. In this project, the battery serves as the power source being monitored to measure its voltage, current, capacity, and remaining charge, allowing users to assess battery performance and manage its usage effectively.

Wires carry current between the battery terminals, the shunt, and the load. Since the system supports up to 100A of current, wires used on the high-current path (battery to shunt to load) must be rated for the expected maximum current to prevent overheating or voltage drop errors in the measurement. The shunt-to-display connection is handled separately by the USB-USB male-to-male cable, not by additional signal wiring.

Wire the components using the table below.

Assembly Instructions

Follow these steps to operate the PZEM-037 correctly after the hardware connections are complete.

Once the battery is connected to B+ and B−, the PZEM-037 powers on automatically and the LCD display activates. The screen will display the battery symbol, voltage, current, capacity, and percentage readings within a few seconds. No button press is required for basic operation.

Before taking measurements, set the correct current range to match your current sensor specifications.

1. Press the OK key for 2 seconds to enter the range setting interface.
2. Press + or − to select the correct current range according to your sensor.
3. If no key is pressed for 2 seconds, the system will automatically save and exit the setting interface.

Set the battery's rated capacity in Ah so the PZEM-037 can calculate the remaining percentage accurately. There are two methods depending on whether you know the battery's capacity or not.

Known Capacity

Unknown Capacity

This setting defines the voltage thresholds that tell the PZEM-037 when the battery is considered fully charged (F) and fully discharged (L). It is mainly used to avoid excessive discharge of the battery.

How to set F and L:

1. Press − and OK keys simultaneously for more than 2 seconds until the number on the screen flickers, then release the key.
2. Press + or − to adjust the F (Full/High) voltage value to match your battery's full charge voltage.
3. Release the key, then press OK to confirm and move to the L (Low) setting.
4. Press + or − to adjust the L (Low) voltage value to match your battery's minimum safe discharge voltage.
5. Release the key to save and exit.

Recommended values by battery type:

Before starting a new test session, reset the capacity counter to ensure readings are not combined with data from a previous session. There are two methods:

• Method 1 — Fully charge the battery, then long press the + key to set it to full capacity.
• Method 2 — Fully discharge the battery, then long press the − key to zero the capacity.

With all settings configured, connect your device or load to the C+/L+ and C−/L− terminals. Once the load begins drawing current, the PZEM-037 will immediately update all readings in real time:

• Voltage (V) — reflects any sag under load
• Current (A) — shows how much current the load is drawing
• Capacity (Ah) — accumulates as the battery discharges
• Percentage (%) — counts down from 100% as the battery depletes

The PZEM-037 displays four values simultaneously on its LCD screen. Here is what each reading means and how to interpret it during a battery test.

The voltage reading shows the current terminal voltage of the battery in real time. The voltage drops gradually during discharge and drops more sharply as the battery approaches empty. A voltage reading significantly lower than expected under light load may indicate internal resistance increase due to battery aging or damage.

The current reading shows how much current the connected load is drawing from the battery at that moment, measured in amperes. A higher current draw means the battery will deplete faster.

The capacity reading shows the accumulated charge that has been removed from the battery since the last counter reset, measured in ampere-hours (Ah). This value increases as the battery discharges and is used by the module to calculate the remaining battery percentage. It is useful for verifying whether the battery delivers its rated capacity during a full discharge cycle.

The percentage reading shows the estimated remaining battery capacity based on the accumulated charge removed from the battery since the last counter reset, compared against the rated capacity entered in the settings. It counts down from 100% as the battery discharges. This reading is only accurate if:

• The correct battery capacity was set in Step 3
• The correct F and L voltage thresholds were set in Step 4
• The capacity counter was reset at the start of the test in Step 5

Provides a quick visual indication of the battery's remaining charge. It fills during charging and empties during discharging, allowing users to easily see the battery status alongside the percentage reading.

The tables below summarize all measurement parameters and physical specifications of the PZEM-037 based on the manufacturer's datasheet.

After completing the hardware connections, verify each of the following to confirm the PZEM-037 is reading correctly before starting a full test session.

With no load connected, the voltage reading on the PZEM-037 should match the battery's open-circuit voltage. Verify this using a separate multimeter set to DC voltage across the battery terminals. A difference of more than 0.2V between the two readings suggests a loose connection on the B+ or B− terminals.

With no load connected, the current should read 0.00A. If the reading stays at 0.00A with a load connected, ensure the shunt is correctly wired in series between B− and the battery's negative terminal.

Confirm the battery capacity is set correctly in the module settings before starting a test. With a fully charged battery and the counter reset, the percentage should read 100%. If it reads a different value after a fresh reset on a fully charged battery, the capacity setting does not match the battery's actual rated Ah and needs to be adjusted.

The PZEM-037 Battery Coulomb Meter successfully demonstrates that accurate DC battery monitoring can be achieved without any microcontroller, software, or programming. By connecting the module directly to a battery through the included 100A pure copper shunt, real-time voltage, current, capacity, and remaining battery percentage readings are available immediately on the built-in LCD display.

The most important aspect of this project is the role of correct wiring and setup before taking measurements. Placing the shunt correctly on the negative current path, setting the battery capacity accurately, configuring the F and L voltage thresholds, and resetting the capacity counter before each session are all essential steps for obtaining reliable readings. Skipping any of these steps produces inaccurate percentage or current readings that do not reflect the battery's true state.

Overall, the PZEM-037 is a practical, low-cost, and easy-to-use tool for battery testing and energy monitoring in DC systems, suitable for students, hobbyists, and anyone working with battery-powered devices who needs accurate real-time electrical measurement without complex instrumentation.

To further improve this battery monitoring setup, the following enhancements are recommended:

• Use appropriately rated high-current wires for all connections on the main current path. Undersized wires introduce resistance that affects measurement accuracy and creates a safety risk under high current loads.
• Add a low-voltage cutoff relay between the load and the battery to automatically disconnect the load when the voltage drops to the battery's minimum safe level, preventing over-discharge damage to Li-ion cells.
  
• Test with multiple battery chemistries to explore how the module performs across different voltage ranges and capacity ratings, since the PZEM-037 supports any DC battery system from 8V to 100V.

• Peacefair — PZEM-037 Battery Coulomb Meter Product Documentation
• Peacefair — PZEM-037 User Manual
• Battery University — Li-ion Battery Discharge Characteristics and Safe Voltage Ranges
• All About Circuits — DC Current Measurement Using a Shunt Resistor

• Joshua T. Colendres
• McRaven B. Batapa