What Is Lead Acid Battery and How Does It Work? A Closer Look

What is a lead-acid battery, you ask? For starters, a lead-acid battery is the most common type of car battery.

It’s also the best battery for many other types of equipment. This includes electric vehicles and cordless power tools.

But, surely, what you really want to know is how a lead-acid battery works. And what are its advantages and shortcomings?

By answering these questions, you can decide whether a lead-acid battery is ideal for your needs. Conveniently enough, the guide below has all the answers you’ve been looking for. Read on to learn what you need to know.

What Is a Lead-Acid Battery?

A lead-acid battery is named after the main components that allow it to work, namely lead and sulphuric acid. The chemical reaction between these two substances either stores or releases electrical energy.

This ingenious technology actually dates as far back as the 19th century. And its design has not changed very much since then. Despite these facts, this common, cheap battery is still very effective for many applications today.

How a Lead-Acid Battery Works

As mentioned, the battery casing houses a controlled chemical reaction between sulphuric acid and lead. The reaction between the two active components causes a flow of electrons (in other words, electricity).

This reaction can be directed to flow in one direction or the other. So, when sulfate from the sulphuric acid bonds to the lead, electricity flows out from the battery. This is known as “discharge.”

The battery is “recharged” when the reaction is reversed. That is, the sulfate separates from the lead and goes back into the acid. As this happens, electricity flows back into the battery.

How Lead-Acid Batteries Wear Out and Die

The reaction described above can be repeated over and over again for a while. Eventually, though, the battery can wear out so that it no longer functions properly or at all.

Specifically, there are certain factors that cause permanent changes to the active components within the battery. Then, the energy-generating reaction is hindered. Here are a few ways this can happen.

Partial Discharge

When the sulfate from the liquid acid bonds to the lead, the level of liquid in the battery lowers. Then, a portion of the lead is no longer submerged in the liquid.

This isn’t a problem as long as the battery is recharged fairly soon after discharging. But if the battery isn’t recharged soon enough, the lead plates remain exposed. In this event, the sulfates begin to bond to the lead permanently.

And then, there is less lead and fewer sulfates available to recharge the battery to full power. This is why it’s always important to recharge lead-acid batteries as soon as you’re done using them.

Deep Discharge

You should never let a lead-acid battery discharge below 50%. This is called “deep discharge.”

When more than half of the battery’s charge is spent, it means that too much of the lead is exposed outside of the acid solution. This causes the lead to become brittle and it starts breaking apart.

The little pieces of lead that break off fall into the liquid and sink to the bottom. Then, there is less lead for the sulfates to bond to and the battery can no longer reach a full charge.

Often, the damage is so severe that the battery can’t charge at all. This is what causes car batteries to die when the headlights are left on overnight.

Damage From Overcharging

You must stop charging a lead-acid battery once a full charge is reached. Continuing to charge a full battery is known as “overcharging.”

This will cause the liquid acid solution to degrade. Then, there won’t be enough sulfates in the solution to power the reaction.

To prevent this, there are some battery chargers that will sense when the battery is full and will automatically stop charging. With all other chargers, be careful to disconnect them manually once a full charge is reached.


You should also know that lead-acid batteries will self-discharge when not in use. This happens very slowly, accounting for a 1% loss in charge per day. Still, remember that your battery will suffer permanent damage (as described above) if it’s not charged often enough.

Additionally, warmer temperatures cause lead-acid batteries to self-discharge faster. Also, when the battery is stored in an inactive device, the device drains a small amount of energy, too.

Advantages and Drawbacks of Lead-Acid Batteries

Self-discharge and a moderate level of maintenance are some obvious drawbacks of lead-acid batteries. They also discharge quite quickly whenever you use them. So they’re not well-suited for long periods of use.

Conversely, they are ideal for appliances that need a quick, powerful burst of energy. That’s why they’re commonly used as auto batteries. They provide a jolt of energy to start the engine and then they recharge as the car is driven.

Most importantly, they’re powerful enough for heavy use. For instance, a fully-charged lead-acid battery can push a golf cart up a hill. Or it can provide the energy necessary for your power drill to drill through several planks of wood.

Furthermore, these batteries are an eco-friendly option, provided that you recycle them as you’re supposed to. And they’re one of the cheapest options, too.

Do You Need Lead-Acid Batteries?

Now that you know all about lead-acid batteries, you can determine whether or not they’re ideally suited for your next project. However, do you know anyone else who might be wondering, “What is a lead-acid battery?” If so, please share this guide with them.

Contact us here to find out more about lead-acid batteries or to ask us any other questions you have. Otherwise, click the Battery Products tab in our menu to find the high-quality batteries you need.