The XH-M239 is a discharge-only battery capacity tester with two 18650 battery bays, although it can test only one 18650 cell at a time. The left battery bay is reserved for its optional internal power supply.
Most other battery testers position the positive pole of the 18650 cells near the operating buttons. This tester is different: it expects 18650 cells to be inserted with their positive pole at the top. While the battery bays do mark the poles, these markings are faint and may be difficult to see.
Overview
This discharge-only test device supports testing a single 18650 cell at a time. A screw terminal on the right side allows for alternate battery holders (or test wires) to accommodate different battery types and sizes, as long as the battery voltage does not exceed 5V.
Due to limited documentation, the implied voltage limit for batteries under test is 5V. However, the ability to set a stop voltage within a range of 1.0–30.0V hints that the device might support batteries with higher voltages than its operating power. This suggests potential for testing a wider variety of batteries, though this has not been verified. If you’re willing to experiment, proceed with caution and at your own risk (you may destroy the device).
Both 18650 battery holders are quite tight, making battery insertion or removal challenging at first. Over time, the holders wear slightly, making it easier to insert and remove cells.
| Feature | Description |
|---|---|
| Channels | 1 |
| Battery Under Test | 5V max: - 18650 battery bay - screw terminal (right side) |
| Power Supply | USB-C |
| Discharge Test | 8 Ohms 10W load resistor: - Max discharge current 500mA - Units: total mAh or total mWh - Stop-voltage configurable (1.0–30V) - no heat sink or fan |
| Charging | no charging |
| Auto-Test | no auto test, manual operation only |
| Off-Button | yes |
| Language | Chinese only |
| Firmware | version unknown |
| LED | no LEDs |
| Display | - monochrome LCD - no backlight |
Although the stop voltage can be configured within 1.0-30.0V, suggesting the potential to test batteries >5V, there is no documentation or PCB labeling to confirm this. Testing batteries >5V may damage the device, so I have not attempted it. If you have additional information, please leave a comment below.
Language
The device operates in Chinese only, with no known option to switch to English. Once familiar with the device’s operation, the language limitation becomes manageable:
If you provide external power via the barrel jack connector on the left side, you may leave the left battery bay empty. The device supports a wide range of input voltage (5-12V).
For portable use, insert a 18650 cell into the left bay to make the device independent of external power supplies.
Display
The device has a large LCD display without a backlight. In bright daylight, the display is very readable, but in dim environments, visibility is poor.
The display is in Chinese only.
Discharge Load
This device uses a 10W 8 Ohm load resistor, differing from most testers that use 4 Ohm. Consequently, it has a moderate maximum discharge current of 500mA, while most other testers discharge at 1A. Testing large-capacity battery cells therefore can take many hours.
Portable Use
The tester includes a dedicated power switch on the right side and a power supply battery indicator in the top right corner of its display, which is helpful for portable use. This feature prevents accidental drainage of the power supply battery, unlike the single-cell all-in-one tester, which lacks both a power switch and a battery indicator, potentially draining the power supply battery to 0V.
Power Supply
Either insert a 18650 cell into the left battery bay or connect an external 5-12V power supply to the barrel jack connector on the left side.
Buttons and Operation
To test a battery, insert it into the right battery holder or connect it via the screw terminal. Power the device using either an external source or a 18650 cell in the left bay, then switch it on with the power switch on the right side.
The display will show the voltage of the battery under test (placed in the right bay) and a battery indicator for the power-supply battery (placed in the left bay).
Setting Stop Voltage
Before testing, set the stop voltage by pressing the + and - buttons. For 18650 cells, a stop voltage of 3.0V is suitable.
For unknown reasons, the device allows for stop voltages in the range of 1.0-30.0V.
Setting Unit
The device can measure capacity in mAh or mWh. Use the left button to switch units as needed.
To compare the actual capacity to vendor specifications, use mAh. For a measure of the true energy stored, use mWh, which accounts for voltage drops during discharge. While you cannot directly compare mAh and mWh, mWh is more accurate for total energy capacity.
Starting/Stopping Test
To start or stop a discharge test, press the second button. The circles in the top of the display will indicate:
- Test Active/No Test: top circle is filled when testing is active, and unchecked when stopped.
- Test Completed: bottom circle is filled when a test completes automatically.
Test results will appear within a few seconds of starting.
Conclusion
This tester is designed specifically for testing fully charged Li-ion cells in a portable manner. Its ease of use, dedicated power switch, and built-in battery indicator make it well-suited for portable use.
The screw terminals also offer flexibility to connect different battery bays or test cables.
No Charging Capabilities
This device is optimized for portable use, so it does not include charging capabilities, which limits its utility for testing:
- Accuracy: A tester with charging capabilities ensures that batteries are fully charged before testing. Without this, test results may be inaccurate.
- Charging Tests: Charging tests allow a tester to charge an almost empty battery while logging the charge input, ending the test with a fully charged battery. By contrast, this tester discharges a fully charged battery to empty, which can be less practical.
Flaws
While functional, this device has some notable limitations:
- Tight Battery Bays: 18650 battery bays are overly tight, requiring force to insert or remove cells.
- Chinese Only: The device lacks English language support and documentation, though this becomes manageable once you understand its operation.
- Ambiguous Settings: The configurable stop voltage range (1.0-30.0V) seems incompatible with its intended use for batteries <5V.
- No Backlight: The large monochrome LCD display is excellent, but the lack of backlighting makes it difficult to read in low-light conditions.
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(content created Nov 09, 2024)