Preparing heavy duty batteries for storage

Any rechargeable battery that will not be used for prolonged periods of time, such as during the winter months, needs to be stored properly to avoid damage to the battery and to ensure longer use before replacement.

Officials at EnerSys, the global leader in stored energy solutions for industrial applications ( and the manufacturer of ODYSSEY batteries ( offer these storage tips:

1. Fully charge the vehicle's battery before placing it into storage to extend its service life.

Maximizing the service life of a battery requires that the battery be properly charged, they say. Proper charging will break up internal sulfation and thereby prevent its buildup in the battery.

Inadequate or improper charging is a common cause of premature failure, they note. Chronic undercharging will cause sulfation to accumulate to a point where a normal recharge will not break it down. This will eventually cause battery failure.

Conventional batteries that are only partially charged when put into storage often experience permanent damage and may not recover to their full capacity, even if they are charged prior to reinstallation.

ODYSSEY batteries, however, can recover from extremely deep discharges and are more forgiving of abusive storage conditions than conventional absorbed glass mat (AGM) or flooded batteries, the officials note. This is achieved through thin plate pure lead technology (TPPL) and proprietary designs/processes.

2. Test the battery to determine the battery's state of charge.

To do this, the EnerSys officials advise using a reliable digital voltmeter to measure the battery's open circuit voltage (OCV). Do not measure the OCV until at least six to eight hours after the battery has been charged to ensure that internal chemical reactions have reached a state of equilibrium.

The battery manufacturer's specifications will indicate what OCV will correspond to 100 percent state of charge.

3. Store the battery in temperatures that meet the manufacturer's recommendations.

The electrolyte in an acid-filled battery may freeze if the battery is stored in low enough temperatures and is not fully charged, the officials point out. Consult the manufacturer's specifications to find the lowest temperature at which the electrolyte remains fluid and the battery can be stored.

Thin plate pure lead, absorbed glass mat-valve regulated lead acid (AGM-VRLA) batteries can be stored for two years, or until the OCV drops to 12 volts, at temperatures of 77 degrees Fahrenheit (25 degrees Celsius) or lower, they say. The lower the temperature, the longer the storage time, as long as the temperature does not drop below the manufacturer's specifications.

As a rule of thumb, an increase in temperature by approximately 18 degrees Fahrenheit (10 degrees Celsius) cuts storage time in half.

The battery should be stored for only one year if the temperature rises to 95 degrees Fahrenheit (35 degrees Celsius), warn the officials. Batteries must be recharged before the OCV drops to the manufacturer's recommended minimum value, regardless of the storage temperature.

Because each type of battery is charged differently, always consult the manufacturer's recommendations before charging and storing any battery.