Put the batteries in a well-ventilated area. Batteries pass off Hydrogen gas that when contained can be explosive.

 

Check the plates in the battery to make sure there is enough electrolyte liquid. Pop the caps off the chambers with a flathead screwdriver. If the liquid is low then fill the chambers with distilled or de-ionized water. Do not over fill the acid will pour out of the battery.

 

Plug a 12-volt battery charger into an outlet. Attach the red charger clamp to the red (+) battery terminal. Attach the black charger clamp to the black (-) battery terminal. Let the charger work for at least 12 hours. Top the charge by letting the battery reach a charge of 14 to 16 volts.

 

Give a float charge by lowering the electric current going into the battery. Let the battery charge at a lower current for 2 to 3 hours.

 

See if the ohms reading on the battery charger register 12 volts after 12 hours of charging. If the reading is less than 12 volts, leave the charger on the battery for another 6 to 8 hours. Read the ohms again on the battery charger; if the charger reads 12 volts, the charge is complete.

 

Pop the caps off the battery chambers after charging and fill with distilled or de-ionized water. Do not overfill.

 

Look for gas bubbles in the battery chambers. If gas bubbles are visible then the battery is almost at full charge. The gas bubbles are a combination of oxygen and hydrogen.

 

Read the temperature in the area where you are going to charge the battery; if the temperature is higher than 85 degrees Fahrenheit then reduce the amount of electric charge. Do not attempt to charge a battery in an area where it is 120 degrees Fahrenheit or hotter.