Battery storage FAQs

Dec. 2, 2016
Answers to some common questions.

Question: Do flooded lead-acid and absorbed glass mat (AGM) batteries have different storage recommendations?

Answer: If storing the vehicle with the battery still connected, attach an automatic maintenance charger to offset the vehicle’s key-off drains, whether it’s either battery type. Attach a charger designed for the battery type.

On older vehicles without sophisticated electronic systems, disconnect the battery cables when storing batteries in the vehicle.

If storing the battery outside of a vehicle, follow the vehicle manufacturer’s disconnection guidelines to protect the computer system.

Q: What needs to be done prior to storing?

A: Inspect the battery for any cracks and corrosion. On flooded batteries check for low electrolyte levels. Then, clean the battery terminals, either with battery spray cleaner or a baking soda/water mix.

If dirt, dust and oil stay on the battery, the battery could self-discharge quicker than if it was clean due to a transient power loss between the positive and negative terminals.

Q: Where should batteries be stored?

A: Always store a battery fully charged in a dry location with adequate ventilation.  The warmer the temperature, the faster the battery will self-discharge.

Flooded lead-acid batteries discharge faster – about 3 to 5 percent a month – than an AGM battery, which discharges about 1 to 3 percent a month. Higher humidity areas can increase the battery’s corrosion.

Fully charging protects the battery from deterioration and freezing solid.

A fully charged lead-acid battery, whether it’s flooded or AGM, will not freeze until the temperature falls to -80 degrees F. However, a completely discharged battery can freeze solid at 32 degrees F.

A discharged battery can undergo sulfation – a process where the battery’s internal components deteriorate because of the lack of charge.

A battery can be kept on an automatic maintenance charger while it is in storage. Regulate the voltage between 13.1 and 13.5 at 1 amp maximum.

Store batteries in an area with adequate ventilation away from flammable liquids. A battery can expel hydrogen and oxygen as it recharges.

Q: Do stored batteries need to be tested periodically to make sure they don’t fall below a certain voltage?

A: Batteries need to be monitored weekly, especially if a charger has been left connected to them. A standard voltmeter can test both an AGM and a flooded battery.

If the battery’s voltage falls below 12.45V, recharge the battery. If the voltage is that low, it means the battery only has 30 to 40 percent charge left.

Q: What needs to be done when taking a battery out of storage and before using it?

A: Check the battery’s voltage to ensure it is fully charged and clean off any terminal corrosion. Typically, readings for a flooded battery should be 12.7V to 12.8V, and 12.8V to 12.95V for an AGM battery.

When taking a flooded battery out of storage, also make sure its electrolyte levels are half an inch above the plates. If they’re low, refill the battery with distilled water and recharge it.

When installing the battery, clean the battery connections and connect the positive cable first.

Source: Interstate Batteries

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