The Lithium Battery True Capacity Tester Module XH-M239 discharges 18650 cells with a current of about 500 mA. It takes about 6 hours to test a single good cell: can we increase the discharge current?
The load is an 8 ohm 10W resistor while the current sensor is a 20 milliohm SMD resistor.
I quickly verified that if I parallel to the load a low-ohm power resistor the current increases and the mAh counter goes faster. So it should be possible to increase the drain on the battery under test and get a consistent result (with the error estimated in the previous post).
Would the circuit handle it? The tracks seem to be thick enough and we can easily measure their voltage drop, for example V across the battery vs V across the load. If we double the current to 1A, the 0.02 ohm sensing resistor would dissipate P = R * I * I = 0.02 * 1 * 1 = 0.02 W. 20 mW is well below the unknown rating of the resistor, which I would assume to be 250 mW.
Any resistor below 10 ohm with adequate power rating (10W or more) will do the trick if soldered in parallel to the stock load. For my quick test I went as low as 2.35 ohm load which resulted in a measured current of 1.5 A.
Note: you do it at your own risk as you understand BOTH stated AND not stated RISKS of this modification (short circuit, explosion, fire, skin burns, end of the World, end of Internet, human race extinction and so on).
Even Li-po cells from laptop battery packs should be able to withstand C to 2C discharge current so this trick is useful for testing a large amount of batteries with just one XM-M239 device.
