How to Properly Store a Car Battery to Maintain Its Charge

Essential Steps to Properly Store Your Car Battery

Storing a car battery properly is crucial to maintaining its charge and ensuring it remains in good working condition when you need it. Whether you’re storing a car for the winter or simply keeping a spare battery on hand, following the right procedures can significantly extend the battery’s lifespan and prevent unnecessary damage. Here’s a comprehensive guide on how to properly store a car battery to maintain its charge.

Why Proper Battery Storage Matters

When not in use, all car batteries gradually lose their charge. This is known as self-discharge, which occurs even in perfectly functioning batteries. Improper storage conditions can accelerate this discharge, leading to a dead battery when you eventually need it. Additionally, improper storage can cause other issues, such as sulfation, where lead sulfate crystals form on the battery plates, further reducing the battery’s ability to hold a charge. If the battery is left in a discharged state long enough, the sulfate crystals harden to the point where the battery can’t be recharged, at which point the battery becomes useless.

Battery self-discharge— How much and how fast?

The discharge rate of a lead acid battery is directly related to storage temperature. If left in a hot garage, for example, it can lose up to 1% of its charge per day. However, if it’s stored in a cool dry spot, the discharge rate can drop down to 3-5% per month. Yet, you don’t want to store your battery in a refrigerant or freezer, either. In other words, avoid the extremes. Stored a battery between 50°F to 60°F is best.

Serious and irreversible battery sulfation begins once the charge drop to 60% to 70%. So, if you store your battery in a cool spot for 10 months without connecting it to a battery maintainer, it will start to sulfate (3% per month X 10 months = 30% loss of charge).

Prepare the battery before storage

1) Clean the battery posts: Use a battery brush to clean corrosion off the positive and negative battery posts. Then apply a light film of dielectric grease to the posts to prevent further corrosion
2) Clean the top of the case: This prevents the migration of stray discharge paths.
3) Charge that battery: Always store a battery with a full charge

Use a battery maintainer to keep your battery fully charged while being stored

A battery maintainer is similar to a trickle charger

Clore/Solar ProLogix PL2140 battery maintainer

but with a big difference; it stops charging when the charge reaches 100%. It then monitors the battery voltage and starts a charge only when needed.

What’s the difference between a battery maintainer, trickle charger and float charger? See this post for the answer.

Car battery storage myths

Myth #1: Never store a battery on a concrete floor

FALSE: Storing a car battery on concrete does NOT damage the battery

Transient power loss occurs any time moisture accumulates on the battery case. It’s not the concrete that causes car battery discharge; it’s condensation/moisture accumulation on the top of the battery case. If you follow the storage recommendations above and keep the battery stored in a cool dry location, it doesn’t make any difference what surface it’s stored on.

Myth #2: A new battery can be stored indefinitely

FALSE: While it’s true that a new battery self-discharges at a much lower rate than a used battery, a new battery should never be stored for longer than two years. Even if fully charged, a new battery will still lose charge and long-term capacity if stored for longer than two years.

For best long-term performance, new batteries should be put into service within 6-9 months of manufacturing.

Deep discharges cause plate degradation in lead acid batteries. Deep discharges shorten the life of the battery.

©, 2023 Rick Muscoplat