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  • Dr. Tobias Weltner
  • Nov 08, 2024

Two Battery-Tester

Semi-Professional Battery Tester Simultaneously Testing Up To 2 Batteries

This battery tester is an enhanced version of the single battery tester reviewed earlier. Unlike the previous model, this tester no longer requires one battery bay for its internal power. Instead, it now runs exclusively on an external USB or 5V power supply.

Overview

While this tester is optimized for 18650 cells, it is compatible with many other battery types. On its back, the mounted battery bays expose their solder pins, allowing you to solder cables and connect additional battery holders. Just ensure that the batteries being tested do not exceed the maximum voltage of 5V.

If you plan to test different battery types, consider the upgraded 4-battery tester. This model offers four channels (instead of two) and includes screw terminals, making it easy to connect a wide variety of batteries and holders without soldering.

The USB-C test connector found on the single-battery predecessor has been removed. Previously used to test USB-C battery banks, this feature was likely excluded because modern battery banks can easily exceed the 5V limit, posing a potential risk.

Feature Description
Channels 2
Battery Under Test 5V max:
- 18650 battery bay
- solder pins (back side)
Power Supply USB-C
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 and now always requires external USB power.

Fan

This tester includes a fan mounted on top of the two load resistors (4 Ohms each). The fan not only covers the load resistors, protecting against accidental burns, but also keeps the resistors at a moderate temperature.

The fan automatically activates whenever any test is running, regardless of the test type. Unfortunately, this means the fan frequently runs when it isn’t needed: during a charging test, the load resistors do not heat up, so the fan’s cooling action is unnecessary.

The fan is connected via a JST XH connector, allowing you to easily add a switch or smart temperature control if the fan noise becomes irritating. That said, the fan produces minimal noise.

Buttons and Operation

The unit is operated via four push buttons. Each battery bay has its own red LED to indicate status:

  • Off: Battery untested
  • Blinking: Battery under test
  • On: Battery test completed

  • Menu Select: (labeled M on the PCB) Short-press to select a menu item. Long-press to start the currently selected test on both channels simultaneously. Unfortunately, there is no option to stop all tests with a single button press.
  • Change Settings: (labeled S on the PCB) Short-press to increment the selected menu item. There’s no decrement option, so continue pressing to cycle back to the beginning.
  • Start/Stop Test: (labeled 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 (clearing the results to zero).
  • Select Channel: (labeled CHN on the PCB) Short-press to switch between channels (1-4). The display shows the selected channel in the upper right corner. All four channels operate independently and simultaneously, regardless of which channel details are shown on the display.

Changing Language

The unit supports English and Chinese. To switch between languages, begin with the unit powered off. Then, press and hold the specified buttons while connecting to power:

  • English: Hold down the 1st and 3rd push buttons, then connect the device to power.
  • Chinese: Hold down the 1st and 2nd push buttons, then connect the device to power.

Test Modes and Settings

The unit offers three test modes, each with specific battery compatibility: AUTO (for LiIon/LiPo), DSG (for all battery types), and CHG (for LiIon/LiPo). These modes can be set individually per channel:

  • Automatic Testing (LiIon/LiPo only): In AUTO mode, the unit sequentially charges, then discharges while logging the current drawn, and then charges the battery again for 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. The battery is left discharged, making this mode 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 functions as a charger specifically for LiIon/LiPo batteries, logging 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 repeated testing cycles, allowing greater measurement accuracy.

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

  • Stop Voltage: In AUTO and DSG modes, a customizable stop voltage can be set for discharge tests. This setting is ideal for protecting battery health across different chemistries (e.g., LiFePO4), as some batteries are more sensitive to 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

The unit allows you to reliably measure a battery’s total capacity through either a Charge Test or a Discharge Test:

  • Charge Test: Ideal if you’ve used the battery until it’s “empty” by your standards. Performing a CHG test logs the charging energy transferred back as the tester recharges the battery.

  • Discharge Test: For higher precision, the AUTO test starts by fully charging the battery to a specified level, then fully discharges it to a safe stop voltage. The tester logs the total energy drawn from the battery. This method provides consistent results by starting from a known charge level but is slower, as it includes three phases—charging, discharging, and charging again—and may increase battery wear slightly.

The Charge Test in CHG mode is faster and reduces battery wear: since the battery would need recharging anyway, the tester functions as a smart charger, logging the energy input. However, the starting charge level isn’t precise and depends on the battery’s “empty” state, as defined by the user.

For a more efficient manual setup, first run a DSG test to discharge the battery to a specific stop voltage, then perform a CHG cycle. This sequence avoids an extra charging cycle. However, the built-in AUTO mode follows the reverse order, which consumes an additional charge cycle.

1. Select Test Parameters

Before testing, set up the parameters as follows:

  1. Channel: Short-press the right button (CHN) to select the channel you wish to use. The battery bays are labeled CHN1 and CHN2 on their top side. Ensure the correct channel is shown in the top right of the display.

  2. Stop Voltage: Set a safe stop voltage for your battery, typically 3.0V for LiIon/LiPo.
    1. Power on the device by connecting it to a USB supply.
    2. Short-press the left button (M) until STOP is highlighted.
    3. Short-press the second button (S) to adjust the stop voltage as desired.
  3. Test Mode: Choose DSG, CHG, or AUTO mode:
    1. Short-press the left button (M) until MODE is highlighted.
    2. Short-press the second button (S) to select the test mode.
  4. Loops: Set the LOOP option. Use 1 for a single loop test.

Your settings are stored until manually changed.

2. Connect the Battery Under Test

Once parameters are set, connect the battery to the selected channel. Each battery bay is marked as CHN1 through CHN4, with matching screw terminals on the back. Ensure that the battery voltage does not exceed 5V, especially when testing power banks.

When inserting a 18650 cell into the battery bay, avoid reversing the polarity, which could damage the device. The positive terminal faces you when viewed from the button side of the device.

Choose one of these connection methods for the battery under test:

  • 18650: Insert an 18650 cell in the right battery bay, or
  • Alternate Battery/Power Bank: Use the screw terminals on the back, connecting an appropriate battery bay or connector.

3. Start the Test

To start testing, use one of these 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 BOTH channels: Long-press the first button (M).

The display’s STA field shows the test status. The test stops automatically upon completion. Pressing the R/S button again will pause or abort the test.

USB-C Power Supply Requirements for Charging

When using CHG and AUTO modes, connect both USB-C ports to external USB power to ensure charging functionality. If only one port is powered, channels connected to the unpowered port will show 0A charging current during tests.

Connecting just one USB-C port may seem sufficient for configuring and reporting test results, but charging current will remain at 0A for channels connected to an unpowered USB-C port. For reliable operation, always connect both USB-C ports to external power.

Test Results

Results display in the lower portion of the screen and update continually:

  • mAh: Capacity in mAh.
  • mWh: Energy capacity in mWh, accounting for battery voltage and voltage drops for an accurate energy measure.
  • mR: Internal resistance in milliOhms. Lower values indicate better quality. For 18650 cells, values should generally be below 80mOhm, while high-drain cells are typically well below 20mOhm.
  • Time: Elapsed time, displayed in hours, minutes, and seconds.

In DSG and AUTO modes, the discharge capacity is measured, while in CHG mode, the charge capacity is logged.

Conclusion

This tester, improved from its predecessor, offers reliable testing for up to two batteries at once and is especially suitable for 18650 cells. For other battery types, consider the 4-battery version with screw terminals for easy connection to alternate battery bays. Note that these testers are limited to 5V, so they cannot test multi-string batteries like 12V packs.

The design and firmware improvements address many of the limitations of the original single battery tester:

  • Hardware: The newer version no longer requires a battery bay for internal power. The load resistors are actively cooled by a fan, which also shields them from accidental contact.
  • Software: Firmware version 5.6 introduces better button shortcuts and multi-channel capabilities compared to version 4.2 in the single-bay tester.

Ideas for Improvement

This device performs well, but a few upgrades could enhance its usability:

  • Smarter Fan Control: Adding temperature control for the fan, or at least a manual switch, would reduce noise by allowing the fan to turn off when discharge testing isn’t active.
  • Dedicated Power Switch: Since the device cannot be turned off via the M button (now assigned to start tests), adding a dedicated power switch would eliminate the need to unplug the dual USB-C connections.
  • Stop All Tests Option: While a long-press on M starts tests on all channels, there’s no corresponding shortcut to stop them all at once. Adding this option would complete the device’s otherwise user-friendly design.

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(content created Nov 08, 2024)

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