Connect the multimeter leads to the battery's terminals (red probe to the battery's positive terminal and black probe to the battery's negative terminal). Take the reading on the multimeter. If the reading shows a value greater than 7V for a 9V battery, the battery is still fit to use.
Description
Specification
The BT3554 can measure the internal resistance of Li-ion batteries; however, the results will include the resistance of the protection circuit that is needed to maintain the voltage and current within safe limits in an LIB.