Many – if not most – riding lawnmowers require a battery to start the lawnmower’s engine. Since the engines on most lawnmowers are gasoline powered, the battery must supply a large burst of energy to turn the engine’s crankshaft and provide voltage to the spark plugs. You can check the voltage of the battery before attempting to start the lawnmower because battery voltage is a good indicator of whether the battery is up to the task or not.
How a Lead-acid Battery Works
A lead-acid battery contains several individual cells, and each cell contains at least one lead plate and one lead oxide plate. Both of these plates are immersed in an electrolyte solution of 36 percent sulfuric acid and 64 percent distilled water. When these plates come into contact with the acidic electrolyte, an electrochemical reaction occurs and a voltage differential is created between the two plates. Each battery cell produces 2.1 volts of electricity.
Battery Cells in Series
Lead-acid batteries that are used in automobiles, tractors and lawn equipment are made up of several cells that are wired in a series circuit. When two or more cells of equal voltage rating are wired in series, it allows the battery to produce voltage that is equal to the sum of the voltages of each individual cell. For example, when three individual battery cells are wired together in series, the voltage of the entire battery is equal to 6.3 volts.
Six-volt or Twelve-volt
Note whether your lawn mower contains a 6- or a 12-volt battery. A 6-volt battery will not provide enough power for a 12-volt electrical system; likewise, a 12-volt battery will damage components within a 6-volt electrical system. Look at the top of the battery to determine how much voltage your battery is rated to produce. If the battery has three vent caps, the battery is a 6-volt battery; if it has six vent caps, the battery is a 12-volt battery.
Battery Voltage Minimums
A fully-charged 12-volt lead-acid battery will provide 12.6 volts of electricity; likewise, a fully-charged 6-volt battery will produce 6.3 volts of electricity. If the battery has not been used for a long time, test the battery voltage by attaching a voltmeter across the battery terminals. If a 12-volt battery provides less than 12.4 volts of electrical power, the battery should be recharged before attempting to use this battery to start a lawnmower. Likewise, if a 6-volt battery provides less than 6.2 volts, you will need to recharge the battery before use.