How to Know if Your T105 Batteries Are Tired

Charge your T105 battery completely. Turn on the lights for about five minutes, if the device your battery powers has lights. If it doesn't, operate the motor for a few minutes. This removes a little of the charge from the battery and enables you to accurately determine if it's tired.

Turn on the multimeter. Turn the dial so it reads volts and select a voltage range. Up to 10 volts is fine for a T105 battery, as it's rated at 6 volts.

Place the two metal sensors on the end of the wires from the meter onto the two battery terminals. The red sensor goes to the positive terminal, and the black one goes to the negative terminal.

Read the meter display. The meter reads above 6 volts if the battery is in good condition. The top reading is likely to be 6.3 volts for a T105 battery. If the reading is 6 volts or under, your battery is tired and needs replacing.

Remove the three plastic caps on the T105 battery. Unscrew them using your fingers or a screwdriver and lift off the caps so you can access the battery cells.

Put the hydrometer into the liquid inside the first cell. Squeeze the rubber bulb on the top of the hydrometer using your fingers then release so some of the liquid is drawn into the tube. Remove the hydrometer and hold it at eye level. The plastic insert is floating inside the tube. Read the specific gravity. This is where the plastic insert is floating; the measurement is on the scale printed on the side of the tube. If the specific gravity is above 1.190, your battery is fine. If it's below 1.190, your battery is tired.

Repeat the process on the two remaining cells, even if the reading is fine for the first cell. If any of the cells has a reading below 1.190, consider replacing the battery. It only takes one tired cell for it not to operate correctly.