To check if a battery is charged with a multimeter set the multimeter to DC voltage.
Then place the red probe on the positive terminal and the black probe on the negative terminal.
When the battery has no draw on it then the battery when fully charged should read between 12.2 volts to 12.6 volts when it's fully charged.
However the battery may also read 14 volts which means it's fully charged as well.
The red probe is for contact with the positive terminal and the black probe is for contact with the negative terminal.
When the probes touch the terminals while the car is off and the battery is resting, the multimeter display should show a reading of 12.2 to 12.6 volts (full charge).
To check the voltage you'll need a voltmeter, which can be purchased cheaply from most major automotive parts stores.
Check the voltage of your battery using the voltmeter to help determine your next course of action. 12.6V volts or above - Your battery is healthy and fully charged.
To test the charging system, hold the voltmeter leads on the battery terminals while you rev the engine to about 3,000 rpm.
The voltage should rise to a value between 13.8 and 14.5 volts, which is the minimum voltage needed to charge a typical 12V battery.
A fully charged battery will typically display a voltmeter reading of about 12.6 to 12.8 volts.
If your voltmeter is showing a voltage anywhere between 12.4 and 12.8, that means your battery is in good shape.
Any voltage above 12.9 volts is a good indicator that your battery has excessive voltage.
Full voltage is 28.7 volts on a 24 volt system.