10 Pack Ultra-Mini USB Type C 3.7V Lithium Battery Charger Board 4.2V Charging Module with Protection Circuit and LED Charge Indicators 5V USB-C Input

I don't know how they can ship and manufacture these for such a low price

I'm using this to keep the town from changing my water meter to something new I'm not set up to read. There was a 7Ahr lithium D-cell in it's transmitter that died after 10+ years. They said it wasn't replaceable but I replaced it with this and a 1000mAhr LiPo I had laying around.. Works fine. Everyone's happy. It draws 1W periodically when the battery needs to be charged. The green and red LEDs are great also. I glance up at it when I go out the basement door and I know if all is good. All fixed for about $1 vs ~$1000 for a new meter and transmitter to be installed on old plumbing in a really difficult location.

Packing needs to be reviewed and the two boards need to be separated in bubble envelopes to protect them, also one did not power on at all, after testing it was determined that one of the components wasn’t allowing power to the rest of the board.

Used this to charge a 3.7 battery in a small boom box I made. Seemed like good quality charged my battery.

Caution with these. Of the six, the first one smoked upon powerup. The second was dead. At that point I returned the items for refund, which was accepted. Be careful...

The ones that worked, work well. They have a great stable voltage range.However, some of the items out of the box were defective. I even followed the instructions and twisted the dial until the clicking sound was had both ways BEFORE any power was applied.So while these are nice when they work, they appear to not always work.

It's easy enough to use this and figure out how to work with it, and it works great. Would be nice to have an actual spec sheet or something telling you how to use the component and its constraints (outside of a short amazon description).

Do not buy this, it is very cheap