A quick look at the PCB shows that the key component is an ST 8S003F3P6 microcontroller. This is an STM8 microcontroller. There is also an 8 pin DIP marked "358", which is most likely an LM358 dual single supply op-amp. The STM8 has 8K of flash and 1K of ram. There is a 12 Mhz crystal nearby. It includes a 10 bit ADC.
I may be tempted to add my own comments to the documentation once I receive my unit and begin using it.
Find a way to connect your battery to the BAT+ and BAT- terminals. Since I want to test 18650, I use a modifed inexpensive single battery charger that provides a handy socket. This is more important than you may think. Long wires and a mediocre connection due to a cheap socket can have a huge effect on test results.
Press the Sk button and the test begins. During the test, the display cycles through:
The heat sink definitely gets hot at the 1.0 amp setting. I am frightened to think how hot it would get set at 2.6 amps. At the end of the test, the device beeps loudly and rapidly
My first candidate was a pink LG cell pulled right off of my Xtar Dragon charger. To my dismay, the tester shows the battery voltage dropping to 3.86 volts immediately and the test ends in only a few minutes with a reported capacity of 23 maH. After the test, the unloaded battery measures 4.13 volts and the Xtar shows it as 82 percent. This battery is all used up!
So, let us try another cell. This one a CGR18650E that has served me well. This looks better, the voltage drops to 4.06. This is a Panasonic cell rated at 2550 maH.
My fluke meter shows 3.59 when the display shows 3.75 My fluke meter shows 3.51 when the display shows 3.67 My fluke meter shows 3.46 when the display shows 3.62 My fluke meter shows 3.36 when the display shows 3.52 My fluke meter shows 3.23 when the display shows 3.39The test ends at 3.0 volts, and it rates this battery at 1127 mAh. The voltage rebounds to 3.67 volts with the load removed. When I put this on my XTAR Dragon and charge it back up, it takes 1040 mAh. So I can average these two values and rate the battery at 1083.
So, there is an offset of 0.16 volts. This means that the battery is actually discharged to 2.84 volts. Some protection circuits I can find specs for set the discharge limit at either 2.4 or 2.8 volts, so I guess 2.84 is OK.
On to a third cell, this one a Panasonic CGR18650AF. These are rated at 2050 mAh when new. This one starts at 4.25 volts but drops immediately to 4.18 under load. The tester claims 931, the XTAR Dragon takes 836 to charge it back up, so I call it 883.
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