How To Tell If A 9 Volt Battery Is Good. Whether your detector uses a 9-volt 9-volt lithium or AA batteries you can test them all. Surprisingly to most people batteries will begin to show signs of weakness once it reaches 80 of its original voltage 12V for a 15V battery and 72V for a 9V battery.
Shop Save Today. How to Test 9V Battery Cell Using Multimeter Measure Voltage. Its not the entire answer the battery typically really starts to spiral down at about 74 V thats abo.
Stick it to your tongue briefly to know for sure.
All batteries are different so 25 hours is an average if it is turned off some times the life will be much longer. Readout for a good battery. But remember you cannot test a 9-volt battery with a multimeter alone. Modern products use CMOS ASICs.
