Bms connection to 18650's

I have a project that runs on 2 series 18650's. And I just got my bms board. Its like this:

From what I gather I have to connect:

BattA- to 0V on bms
BattA+to 4.2V on bms
BattB- to
BattB+ to 8.4V on bms



What is a “BMS BOARD”?? Link? How should we know this?

I think 3S always means 3 cells in series. You have two? BUT what is that BMS stuff??

"BMS" = Battery Management System. (Probably.)

Marcio, haven't you been here long enough to know that we don't like F**ing diagrams? Your is even worse than most, with multiple red lines that seem like they might be important but probably aren't.

Usually the high-current output connection is the last one. The intermediate battery connections are just for low "balance" currents. I have seen similar devices which specify that you can use 2 batteries instead of 3 but all the connections on the board must be used. In your diagram, 8.4V would be tied to 12.6V and 12.6V would be the high-current terminal.

Is there any manual or datasheet for the device?

For that price, can't you find a 2S version?

Sorry, I guess it means battery management system. Here is the link:

US $2.32 20% Off | 3S 40A BMS 11.1V 12.6V 18650 lithium battery protection Board with balanced Version for drill 40A current

So this won't work for me because I got a 3S and I should have bought a 2S?

Next time, please wrap URL tags around your link. When I'm browsing on my phone, it takes me extra steps to copy-paste the link.

It's hard to say from that webpage. There's no detailed manual. There's just enough detail that I would be certain that it does what it says it does. It's a drill motor controller with an additional balance circuit. It only works with specific batteries.

If I had one in front of me, I could work out how to defeat one of the balance elements to make it work with 2 batteries. Since I don't, I would have ordered one that was designed for 2 batteries.

So like this one :

US $1.25 10% Off | 2S 10A 8.4V 7.4V 18650 Lithium Protection Board BMS PCM PCB Li-ion Lipo 2 Cell Pack with Balance Function Charger Protect Module

That looks better. I'm still not sure what you are trying to do but that looks good for 2 batteries.

Im trying to charge 2 lipo batteries in series. I mistakenly bought that 3s one, i guess ill keep it for some future project.