Battery auto-discharge

Auto-discharge

24.03.2017

At Batteries Expert, our motto is "A fully charged battery is a healthy battery!"

A standard lead acid battery (or accumulator) is actually just casing in which electrical energy is stored. Batteries are composed of negative and positive plates submerged in an electrolyte pool (a solution of water and sulfuric acid), which creates a chemical reaction that generates tension (voltage).

When a battery is discharged, its acid level and tension decrease. When the chemical reaction is weak, the energy is low.

Why does my battery lose its charge?

A battery is an active material, kind of like your body! If you remain seated, you save more energy than if you were to engage in physical activity. However, you still use up energy through the simple act of breathing. For a battery, this phenomenon is called self-discharge.

What is self-discharge?

Self-discharge is not a manufacturing defect. All batteries lose their charge while stored due to an internal leakage between the positive and negative plates. At times, the battery may have such a low charge that it can no longer provide enough usable tension.

That is why it is key to know the battery's discharge capacity and recharge it once it has reached 50% depth of discharge (DOD). This is especially true for batteries kept in storage. If you neglect them, stored batteries are likely discharge and stay that way. So remember to charge your stored batteries!

What is a stored battery?

A stored battery is a battery that isn't used often. Here are some examples:

A battery sitting on a shelf in a store. At Batteries Expert, we periodically charge our batteries to ensure that you get a healthy battery.
A battery that's used seasonally and remains unused for months at a time, for example in RVs, ATVs, motorcycles, boats, lawn tractors, golf carts, etc.
A battery in a vehicle that isn't driven far and remains unused for long periods of time.

How can I tell when my battery needs to be charged?

Every battery has a different self-discharge rate based on its type, design, age, and the temperature it's stored or used at. The average daily self-discharge rate for a standard battery is 0.5 to 1%. Some batteries, such as Absorbent Glass Mat (AGM) batteries, have a lower self-discharge rate and hold their charge longer.

Check your battery's state of charge to see if it needs to be recharged. You can test your battery's state of charge quickly and easily with a densimeter (also known as a hydrometer) or a voltmeter.

*A standard starter battery at rest (in storage) is 100% charged when it has 12.65 V of tension.

How often should I check my stored battery's state of charge?

We recommend checking and recharging your battery every three months. However, the older a battery is, the higher the self-discharge rate. That is why it is important to recharge older batteries more often, with a charger that was designed for your battery type and use.

Ask an expert at your local Batteries Expert for advice on selecting the right tester and charger to suit your needs and battery. Or click on the following link for tips on how to choose the right charger.

What will happen if I don't recharge my battery?

You have likely heard of sulfated batteries. Letting a battery lose its charge can damage it due to a process called sulfation. As a battery loses its charge, lead sulfate forms on its positive and negative charging plates. When a battery loses too much of its charge, it lowers the concentration of sulfuric acid in the electrolyte, causing the lead sulfate to crystallize on the plates instead of remaining liquid in the electrolyte. This affects the battery's ability to recharge effectively.

Here are a few situations that could cause battery sulfation:

Failure to fully recharge your battery on a regular basis.
A low concentration of sulfuric acid in your battery's electrolyte.
Storing your battery with low tension for a prolonged period of time.

*Battery sulfation will definitely shorten battery life!

How long will my battery last if I keep it healthy and fully charged?

Keeping your battery fully charged will maximize its life and prevent early failure. To maximize your battery's life, perform proper maintenance charges on a regular basis. This will keep it active and ready for use throughout its expected lifespan.

When regularly maintained, every battery has a certain number of expected life cycles, though this number varies depending on battery type and design. Once a battery has reached the end of its life, not even the best charger can revive it!

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Battery auto-discharge

Auto-discharge