TP5100 2A 4.2v/8.4v 1S/2S Lithium Battery Charger

Sigh, copy the description and the internet thinks you're a spam site...

 https://www.amazon.com/dp/B07S2RCT71?ref=ppx_pop_dt_b_asin_image&th=1

Description:
TP5100 is a double switch buck 8.4V, single cell 4. 2V lithium battery charge management chip. Its ultra-compact QFN16 package and simple external circuit, making TP5100 ideal for portable equipment so large current charging management applications.Meanwhile, TP5100 built-in input overcurrent, undervoltage protection, over temperature protection, short circuit protection, battery temperature monitoring, reverse battery protection.
TP5100 have 5V-18V wide input voltage, dual battery trickle charge into pre-charge, constant current, constant voltage three phase, pre-charge current trickle charge current through an external resistor adjustment, the maximum charge current up to 2A. TP5100 with a frequency of 400kHz switching mode makes it possible to use a smaller outer Suo device and the large current charging still maintain a smaller amount of heat.
TP51OO built-in power PMOSFET, anti-intrusion circuit, so no anti-intrusion protection and other external Schottky diode.

Maximum Ratings:
Static input supply voltage (VlN): 20V
BAI: -8.4V-20V
BAT Short-Circuit Duration: Continuous
Operating environment Temperature range: -40 ° -85 °
Storage temperature range: -65 ° - 125 °

Note:
Voltage settings to operate in the power-off state, the installation of the switch must also disconnect the input and then switch.
Can also be used for white LED constant current drive: Set a single lithium drive, set double lithium drive 2 strings.

4.0 out of 5 stars Markings on board are WRONG - Correct diagram here (But they work great!)

The first one I opened had no markings for Power-In or Battery, positive or negative. I looked up the datasheet for the TP5100, and created a wiring diagram. (Make sure your board matches.)

UPDATE: The other two boards do have markings, but they are WRONG - the input and output are reversed. Connecting it backwards doesn't break anything, but it doesn't work. THE DIAGRAM I'VE PROVIDED IS RIGHT; THE MARKINGS ON THE BOARDS ARE WRONG.

The "SET" gap is to pick 1S (one Lithium-Ion cell) or 2S (2 cells in series) operation - open for 1S, or bridge the gap with solder for 2S. For 1S operation, voltage can be 5-18v. For 2S operation, must be 9-18v.

They work great, charging my 2S battery pack starting at about 0.8A with a 12V input.

2.0 out of 5 stars Wiring it like this.Verified Purchase

It's a very sensitive board because if you connect the wrong way IN or OUT it will be burn immediately so fallow the picture that I mentioned. Attention: some of these boards made by counterfeit IC and not working at all.