"Mr Macaw" wrote in message news
On Sun, 10 Jan 2016 22:13:27 -0000, Ian Field
wrote:



"Mr Macaw" wrote in message
news
I've seen inside drill batteries before (NiCad ones) and there's usually
just three terminals to the pack, -ve, +ve, and one for the temperature
sensor. But this one has a 4th pin, which is connected to the -ve of
the
batteries via a 10K resistor. What is its purpose?

https://www.dropbox.com/s/1np3y4ubr4....jpg?dl=0&s=sl

Bottom left large pin is connected to -ve of cells and one end of the
temperature sensor (a little black blob) and one end of the 10K
resistor.
Right large pin is connected to +ve of cells.
Top left large pin is connected to the other end of the temperature
sensor.
Small pin is connected to the other end of the 10K resistor.

I don't have access to the charger for this pack, I only bought this
pack
to take the cells out to replace them in my own battery pack, as this
one
was half the price.

If your battery pack doesn't have one - don't worry about it.

I know, I was just wondering what it was used for.

Someone else suggested identification - the tool could measure that resistor
to see if its what's expected. It looks like 1% tolerance which would make
sense in that context.

If its a cheap knock-off battery, that resistor could be pretending to be a
temperature sensing thermistor at within spec temperature.