Open the battery compartment in your emergency lights. All emergency
lights vary; some you remove by unscrew the top part that contains the
light bulb, others you need to remove a side or base panel.
Remove the batteries from the emergency light battery compartment. You need to test each battery separately, as
all the batteries need to have an equal charge. One bad battery affects
the power you get from the battery pack.
Look on the label of one of the batteries to ascertain its mAh when
fully charged. It's usually printed near to where the voltage is given
and the battery type. If the mAh isn't mentioned, then you can test the
voltage of the battery instead, but it's not as accurate, as voltage
remains steady until the battery is about 75 percent discharged; mAh
drops as the battery gets used.
Place the metal probes on the ends of the two colored wires from the
meter onto the battery terminals. Put the red probe on the battery
terminal labeled with a plus sign and the black probe on the terminal
labeled with a minus sign.
Check the meter reading. The mAh is the same as the mAh on the battery
label if it's fully charged. If you're using voltage, it's the same as
the voltage on the label unless the battery is nearly discharged. If the
voltage is less than on the battery label, get a replacement.