I have been seeing many lithium ion battery management boards on both eBay and Amazon, and am trying to find out what they do and don't do before I begin using them. I ao have many that are in trash batteries. For example, do they control peak voltage to the cell without external regulation? IE, how safe are they to use?

 

It probably will be more productive to discuss a particular board. It is particularly important to know whether that board is designed or used for single cells or multiple cells.

I have seen some that use an older (TI?) chip. That part number is given. In others, more recent chips are used, such as those from Microchip (examples: MCP738xx) and TI (examples: BQ21xxx and BQ24xxx). All of the those chips are widely used for single cell charging.

 

Yes they work, i have a 3 cell bms pcb with 18650 cells, connected to a 13V supply no problems.

 

Some insight may be provided by the following note:

http://www.ti.com/lit/ug/tidueu4/tidueu4.pdf?&ts=1589112027761