3 terminals on Li Ion Battery

[Greorge]

What is significance of 3 terminals on Li-Ion battery?

It is Nokia  BL-4 3.7V battery

It doesn't last long enough in phone, so I repaced it, but I want to use it for LED or something.
Is it OK just to find + and - and chage and not worry about the third one?

[Psi]

The 3 connections are +,  - and BSI   (Battery Size Indicator, or sometimes Battery Sensor Indicator)
It's a resistor which the phone can use to detect the battery size.

eg, 5k might indicate 1Ah and 10k might indicate 1.5Ah for example.

So yes, you can just ignore the BSI pin.

[Greorge]

Thank you very much for help.