How to find a bad sub-c battery in a battery pack

Discussion in 'General Electronics Chat' started by mrel, Jan 15, 2010.

  1. mrel

    Thread Starter Senior Member

    Jan 20, 2009
    I have Ryobi cordless drill 18v battery Pack.
    How do i find the bad sub -c battery in the battery pack ,there is 15 sub-c battery at 1.2 volt to make 18 volts.
    I charge the battery using the charger that come with the drill.
    After charge the battery a week later ,the voltage drop way below 18 volts.
    I don't know how many of the sub-c battery is bad.
    So any idea on how to find the bad sub -c batter in a battery pack?
    Thank for the help
  2. praveesh

    New Member

    Jan 15, 2010
    You can open the battery and can check the voltage output of each sub C battery units using a multimeter.
  3. 3ldon

    Active Member

    Jan 9, 2010
    short each cell with an amp meter, and a .05 ohm resistor, combined with the resistance of the meter leads, (another typically .05-.1 ohms) you should see at least 10 amps, and this should be fairly consistent with each cell. (+/- 15%)

    there is no need to worry about the cells exploding, this is only 2-4 x what the motor draws anyway.