How Does a Lead Acid Battery Work?

Since you’re reading this, you obviously have some questions about lead-acid batteries. For instance, how does a lead-acid battery work? For that matter, what exactly is a lead-acid battery?

Are these batteries still efficient enough for certain uses or are they obsolete? How do they compare to other batteries?

Fortunately, we have all the answers you’ve been looking for right here in this guide. To start with, we can assure you that these batteries are not obsolete. There are, in fact, many applications in which it’s ideal to use lead-acid batteries.

We’ll explain this in more detail below. We also provide a comprehensive explanation about what a lead-acid battery is and how it works. Read on to learn all there is to know about lead-acid batteries.

What Exactly Is a Lead-Acid Battery?

A lead-acid battery is a rechargeable battery that uses lead and sulphuric acid to function. The lead is submerged into the sulphuric acid to allow a controlled chemical reaction.

This chemical reaction is what causes the battery to produce electricity. Then, this reaction is reversed to recharge the battery.

Believe it or not, this technology is over 100 years old. However, it has been improved upon since its invention in 1859 and it now works more efficiently.

How Does a Lead-Acid Battery Work?

To put it simply, the battery’s electrical charge is generated when the sulphate in the sulphuric acid becomes bonded to the lead. The electrical charge is replenished by reversing this reaction. That is, the sulphate goes back into the sulphuric acid and, thus, the battery is recharged.

Now, obviously, there’s a finite amount of sulphate ions in the acid. And the available surface area of the lead it bonds to is limited, too. So, as the sulphate is depleted, the charge becomes weaker.

For this reason, lead-acid batteries are not ideal for powering devices for a long period of time. Instead, they’re best for applications that need a short, powerful burst of energy.

The Self-Discharge of a Lead-Acid Battery

One unfortunate disadvantage of lead-acid batteries is that the chemical reaction described above can never be halted completely. In other words, these batteries will continue to discharge even when they’re not in use.

Normally, this self-discharge happens somewhat slowly, around 1% lost per day. But certain factors will increase this rate. For instance, the warmer the battery is, the faster it self-discharges.

Also, some devices use a little of the battery’s charge even when they’re turned off. The audio settings in your car are a good example of this. Your car radio uses battery power to “remember” these settings.

In any case, you’ll have to make sure you recharge your lead-acid batteries every once in a while or they will die.

The Death of a Lead-Acid Battery

So, what causes a lead-acid battery to die? Certain factors can damage or change the materials that are needed to cause the necessary chemical reaction. One such factor is allowing the battery to remain in a partially discharged state for too long.

Partial Discharge

As the battery discharges, it lowers the amount of electrolyte solution (the sulphuric acid mixed with water). This leaves the lead plates partially exposed.

If they remain exposed, the sulphate that is already bonded to the lead can harden. Then, it remains on the lead permanently, which decreases the battery’s ability to recharge.

This partial discharge is a common problem with car batteries. You see, the battery recharges when you drive. But if you don’t drive often, or you always make very short trips, your battery might never get fully recharged.

Deep Discharge

Another common cause of battery death is deep discharge. This is when your lead-acid battery is discharged below 50%.

When this happens, small pieces of the lead plates can actually break off and sink into the electrolyte solution. Then, there is less material available to cause the chemical reaction. If too much is broken off, the reaction won’t happen at all.

This is why your car battery becomes unusable if you accidentally leave the headlights on overnight. Even if you’re able to jump-start the dead battery, the damage has already been done. The battery is permanently ruined and will have to be replaced.


Overcharging happens when you keep charging a battery that’s already full. Doing this can break down the material of the electrolyte. Once this happens, there is no sulphate left to bond with the lead.

This is why you don’t want to keep a lead-acid battery plugged into a charger all the time. It’s better to only plug it in once in a while.

Pros and Cons of Lead Acid Batteries

Lead-acid batteries have powerful voltage for their size. Thus, they can power heavy-duty tools and equipment.

They can even power electric vehicles, like golf carts. However, in this case, you’d need to be careful to charge the battery often enough (and without overcharging it). If you don’t, the vehicle will die before reaching its destination, which will also damage the battery.

Additionally, lead-acid batteries are great for starting motor vehicles. They provide an intense jolt of energy to start the vehicle and then they recharge as the vehicle drives.

On the other hand, they are not good for devices you wish to use for long periods of time, like cell-phones. Also, they self-discharge when not in use, which will eventually kill the battery.

In other words, you can’t just leave them sitting around. Thus, they are a bad option for any application that will not be used frequently.

What Will You Use Lead-Acid Batteries For?

Now that your questions are answered, use this guide to determine if lead-acid batteries are the right choice for your needs. Also, do you know anyone else who’s wondering, “How does a lead-acid battery work?” If so, please share this guide with them.

For related reading, check out Inside a Battery: How It All Works.