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  • Dr. Tobias Weltner
  • Nov 08, 2024

Four Battery-Tester

Semi-Professional Battery Tester Simultaneously Testing Up To 4 Batteries

This battery tester is an upgraded version of the simple one battery-tester reviewed earlier. It uses all four battery bays for testing and can test up to four batteries simultaneously. It reliably identifies counterfeit batteries and true battery capacity and health.

Overview

While this tester is optimized for 18650 cell analysis, it can be used with many other battery types: thanks to its screw terminals, you can easily attach alternate battery bays that suit the battery types you want to test. Just ensure that the batteries under test do not exceed the maximum voltage of 5V.

The USB-C test connector that was present on the single-battery predecessor has been removed. This connector was initially used for testing USB-C battery banks, but with modern battery banks often exceeding the 5V limit, keeping this option could have posed a risk.

Although you can still test battery banks, you would now need to design your own USB adapter to fit the screw terminals. Be sure to implement appropriate measures to ensure that the adapter does not trigger higher voltage protocols.

Feature Description
Channels 4
Battery Under Test 5V max:
- 18650 battery bay
- Screw Terminal (back side)
Power Supply 2x USB-C (each USB-C serving two battery bays)
Discharge Test 4 Ohms 10W load resistor:
- Max discharge current 1A
- Units: total mAh or total mWh
- Stop-voltage configurable (2.5–3.5V)
- Fan (runs continuously, no temperature control)
Charging - LiIon and LiPo only
- Max charging current 1A
Auto-Test Yes, charge-discharge-charge cycle with total discharge energy reported
Off-Button no, disconnect USB-C to power off
Language English and Chinese, configurable
Firmware - Version 5.6
- User cannot upgrade firmware
LED one red LED per battery bay:
- off: no test
- blinking: test running
- on: test completed
Display - Color-TFT
- Backlight

Power Supply

Unlike its single-battery predecessor, this device no longer uses an internal battery for power supply and always requires external USB power.

Both USB-C connectors serve as power input, and you can connect either one. However, during charging, each USB-C connector supplies power to only two battery bays, and you would need to connect external power to both USB-C connectors if you want to use all four battery bays at the same time:

  • Left USB-C: supplies charging power to the left two battery bays
  • Right USB-C: supplies charging power to the right two battery bays

Since this tester can work with four batteries at the same time, it may draw considerable power: when all four battery bays are charging at the same time, this may cause currents of up to 4A. Make sure your 5V power supply is capable of delivering this much power, or do not use all four channels simultaneously to charge the batteries under test.

Fan

This tester has a fan that is mounted on top of the four load resistors (4 Ohms each). Thanks to the fan covering (and cooling) the load resistors, there is no risk anymore for accidental burns, and the resistors stay at moderate temperatures.

The fan is turned on automatically whenever (any) test runs, regardless of the type of test. That is unfortunate because the fan frequently runs when it makes no sense: if you are running a charging test, the load resistors are not heating up, so the running fan isn’t doing any good.

The fan is connected with a JST XH connector, so you can easily add a switch or smart temperature control should the fan noise bother you. There is not much noise generated by the fan, though.

Buttons and Operation

The unit is operated via four push buttons:

  • Menu Select: (marked M on the PCB) Short-press to select a menu item. Long-press to start the currently selected test on all four channels at once. Unfortunately, there is no way to stop all tests on all channels with a single button press.
  • Change Settings: (marked S on the PCB) Short-Press to increment the currently selected menu item. There’s no decrement option, so continue pressing until the settings cycle back to the beginning.
  • Start/Stop Test: (marked R/S on the PCB) Short-Press to start, pause, or resume the selected test. Long-press to stop and reset or reset and start (setting the results to zero).
  • Select Channel: (marked CHN on the PCB) Short-Press to switch to a different channel (1-4). The display always shows the selected channel in its upper right corner. All four channels run independently and simultaneously, regardless of which channel details the display currently shows.

Changing Language

The unit supports English and Chinese. To switch between languages, follow these steps:

  • English: keep the 1st and 3rd push button pressed, then connect the device to power.
  • Chinese: keep the 1st and 2nd push button pressed, then connect the device to power.

Test Modes and Settings

The unit offers three test modes: AUTO, CHG, and DSG:

  • Automatic Testing (LiIon/LiPo only): In AUTO mode, the unit sequentially charges, then discharges while logging the drawn current, and then charges the battery again to provide a full capacity assessment. The battery is left fully charged at the end.

    To select AUTO mode, press the M button until the Mode menu is highlighted, then press S until AUTO appears.

  • Discharge Test (all battery types): In DSG mode, the unit starts discharging and logs the discharged energy. It then leaves the battery discharged, so this mode is suitable for non-LiIon/LiPo batteries like LiFePO4 or NiMH that cannot be safely charged with this device.

    To select DSG mode, press the M button until the Mode menu is highlighted, then press S until DSG appears.

  • Charge Test (LiIon/LiPo only): In CHG mode, the unit serves as a charger specifically for LiIon/LiPo batteries, and logs the charged energy.

    To select CHG mode, press the M button until the Mode menu is highlighted, then press S until CHG appears.

Additional test settings can be adjusted for further customization:

  • Loops: In AUTO mode, set up to 10 consecutive loops for enhanced accuracy.

    To set loops, press the M button until the Loop menu is highlighted, then press S to cycle through the number of loops (1–10).

  • Stop Voltage: In AUTO and DSG modes, a stop voltage can be defined for discharge tests, ideal for different battery chemistries (e.g., LiFePO4) or to prevent deep discharge.

    To set stop voltage, press the M button until the Stop menu is highlighted, then press S to adjust the stop voltage (2.5–3.5V in 0.1V increments).

Performing Battery Capacity Test

You can reliably measure the total battery capacity by either discharging a fully charged battery or charging a fully discharged one:

  • Charge Test: This approach is efficient if you use the battery until it’s “empty” by your standards, then perform a CHG test. The tester logs the charging energy transferred back into the battery as it recharges.
  • Discharge Test: For higher precision, use the AUTO test. Here, the tester first fully charges the battery to a specified level, then fully discharges it to a safe stop voltage. In this test, the device logs the total energy drawn from the battery.

The discharge test using AUTO mode starts the battery from a defined level, producing consistent results. However, this test takes longer as it includes three phases—charging, discharging, and charging again—and slightly increases battery wear.

The charging test in CHG mode is faster and reduces battery wear: since the battery would need recharging anyway, the tester simply functions as a smart charger, logging the energy input. The drawback is that there’s no set start level, making the “empty” state subject to user interpretation.

For a more efficient manual testing setup, first run a DSG mode test to discharge the battery to a specified stop voltage, then follow up with a CHG cycle. This way, the battery charges from a defined “empty” state without unnecessary wear. However, the built-in AUTO mode runs the opposite sequence, consuming an extra charge cycle.

1. Select Test Parameters

Before testing, follow these steps to select the test mode and its parameters:

  1. Channel:
    Short-press the right button (marked CHN) to select the channel you want to use. The battery bays are labeled CHN1 to CHN4, which also corresponds to the screw terminals on the backside. Ensure that the correct channel number appears in the top-right corner of the display.

  2. Stop Voltage:
    Set a safe stop voltage for your battery. 3.0V is generally safe for LiIon/LiPo batteries.
    1. Turn the device on by connecting it to power.
    2. Short-press the left button (M) until the STOP setting is highlighted in red.
    3. Short-press the second button (S) until the display shows the desired stop voltage.
  3. Test Mode:
    Select the test mode: DSG, CHG, or AUTO.
    1. Short-press the left button (M) until the MODE setting is highlighted in red.
    2. Short-press the left button (S) until the desired test mode is displayed.
  4. Loops:
    Set the LOOP option. Generally, set this to 1 for a single loop test.

All settings are permanently stored and will stay active until manually updated.

2. Connect Battery Under Test

Once you have set the test parameters, connect the battery to the channel you have just configured. All four channels can be configured independently, so ensure the correct battery is connected to the corresponding channel. The battery bays are clearly marked as CHN1 through CHN4, which also applies to the screw terminals on the back side.

Ensure the battery voltage does not exceed 5V, especially when testing power banks.

When inserting a 18650 cell into the battery bay, be extremely careful not to reverse polarity, as this may destroy the device. The polarity is marked inside the battery bay: the positive pole is facing you when looking from the side with the push buttons.

These are your choices for connecting the battery under test:

  • 18650: Insert an 18650 cell in the right battery bay, or
  • Alternate Battery/Power Bank: Attach wires to the screw terminal on the back of the appropriate battery bay, and attach a suitable connector or alternate battery bay.

3. Start the Test

To start a test, these are your options:

  • Start/Continue current channel: short-press the third button (R/S)
  • Start/Reset current channel: long-press the third button (R/S)
  • Start/Reset ALL channels: long-press the first button (M)

The display’s STA field shows the test status. The test stops automatically upon completion. Pressing the right button again will pause or abort an ongoing test.

USB-C Power Supply Requirements For Charging

Keep in mind that tests involving charging (CHG and AUTO) need a specific USB-C port to be connected to external USB power once charging is activated. If the required USB-C port is not connected to external USB power, charging current for this channel remains at 0A.

This may be have been confusing, so let’s elaborate: if you connect just one USB-C connector to external USB power, then all four channels seem to work just fine, report test results, and can be configured alright. However, once any of your tests invokes charging, then the charging current will always stay at 0A for those channels that are served by the disconnected USB C port. To play simple and safe, make sure you connect both USB-C connectors to external USB power.

Test Results

Test results are shown in the lower portion of the display and are continually updated throughout the test:

  • mAh: Capacity in mAh.
  • mWh: Capacity in mWh, accounting for battery voltage and voltage drops for an accurate energy measure.
  • mR: Calculated internal resistance of the battery in milliOhms. Lower values indicate better quality; for 18650 cells, typical values should be below 80mOhm, and for high-drain cells, they should be well below 20mOhm.
  • Time: The elapsed time for the current test, displayed in hours, minutes, and seconds.

Test Results Display

Test results are constantly updated while a test is in progress. In the modes DSG and AUTO, the discharge capacity is measured. In the mode CHG, the charge capacity is measured.

Conclusion

This affordable tester has matured considerably from its one-battery predecessor, both in hardware and in firmware, and is an excellent choice: it reliably tests up to four batteries. While it is optimized for 18650, its four screw terminals can easily be connected to alternate battery bays and cater all needs.

The design flaws of the original single-battery tester have all been fixed:

  • Hardware: no longer is a battery bay wasted as internal power supply, and all four bays can be used for testing. The load resistor got active cooling through a fan, and the fan covers the resistors so you can’t accidentally touch them and get burned.
  • Software: the firmware version 5.6 indicates the improvements made. The original single-battery tester uses version 4.2. The new firmware has clever button shortcuts and new features required for multi-channel operation.

If you don’t need four channels but would like to benefit from all these improvements, then a smaller two channel version is also available that runs the same firmware version 5.6.

Ideas for Improvement

Although this device works nearly flawlessly, there is still room for improvement, either by the vendor or by users willing to optimize their setup:

  • Smarter Fan: While the fan isn’t excessively loud, it can be noticeably distracting. Implementing temperature control—or at least adding a manual switch—would make it more efficient. Additionally, enhancing the firmware to automatically turn off the fan when no discharge test is taking place would help reduce unnecessary noise and improve overall device efficiency.

  • Dedicated Power Switch: Currently, the device cannot be turned off conventionally. A long press of the M button starts tests on all four channels, but the only way to power off the device is by disconnecting the external USB power supply. Since two USB power connections are required for full functionality, this means pulling out two plugs. Adding a dedicated power switch would greatly enhance usability and make the device more user-friendly.

  • Stop All Tests: While it’s convenient to start tests on all channels simultaneously by long-pressing M, there is no option to stop all running tests at once. Implementing a feature that allows the user to stop all tests in one action would complete the otherwise good usability and improve control over the testing process.

  • Better Power Supply: The device is an evolution of the original single-battery tester. While a 5V power supply worked well for a single-channel tester, a four-channel setup draws considerably more current, which typical USB power supplies may struggle to provide. A redesign of the power supply to support a higher voltage, such as 12V, would be beneficial. When charging four batteries simultaneously, the device can require up to 4A at 5V (20W). With a 12V power supply, the current draw would be reduced to 1.6A (20W), and 12V power supplies are more readily available and efficient.

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(content created Oct 28, 2024 - last updated Nov 08, 2024)

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