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How Do Lead Acid Battery Chargers Work?

Power - by Bryan Veldboom - updated on 2/24/2022

Using a charger to charge a lead acid battery

Rechargeable batteries are all around us, in our cars, phones and laptops. Chances are pretty good you've already used one thing that's powered by a rechargeable battery today. While the batteries themselves may vary, the one thing they all have in common is their reliance on battery chargers. Battery chargers help recharge batteries by reversing the chemical processes that enable them to provide power in the first place. Today we'll take a close look at the science behind battery recharging. We'll explain the dangers posed by under and overcharging your battery, discuss different charging methods and review the different types of battery chargers available.

What are the Components of a Battery?

Obviously, there are too many different types of batteries to discuss in one place, so for our purposes here we'll be focusing on lead acid batteries. Lead acid batteries are used in a variety of applications, however, they are most commonly used as starting batteries in cars, trucks, boats and other vehicles.

Before we get into recharging though, we need to walk through the basics of how a lead acid battery works. The interior of a 12 volt lead acid battery is divided into 6 separate cells. Each cell contains a series of rectangular grids holding a number of lead plates. The grids are arranged in an alternating series of positively and negatively charged grids, each of which is divided by a separator. The battery also contains a sulphuric acid solution called an electrolyte which reacts with the material on the positively and negatively charged grids.

How Does a Battery Charge and Discharge?

When the battery is connected to a load and switched on, it causes a series of chemical reactions inside which convert lead, lead oxides and acid from the electrolyte into free electrons, water and lead sulfates. For a more in-depth look at this process, check out our blog entitled "How Does a Car Battery Work?" When the battery's voltage drops to the point where it can no longer deliver electricity, it has been discharged.

Battery chargers work by reversing the chemical processes that allowed the battery to provide electricity in the first place, restoring the components to their original state. During the recharging process, the sulfate in both the positive and negative plates are split back into their original lead and sulfate. The water left over from the electrolyte is divided into hydrogen and oxygen. The sulfate in the plates combines with the hydrogen in the water, restoring the electrolyte to its original state as sulfuric acid is formed. While this is happening, the oxygen in the water will also combine with lead on the positive plates to form lead dioxide. When this process is complete, the battery has been recharged and can be used once again.

What are the Dangers of Under and Overcharging Your Battery?

When charging a battery, it's important to avoid both under and overcharging it. If you apply too little current, the battery will remain undercharged. When a battery is undercharged, the chemical processes aren't allowed to complete and lead sulfate remains on the battery's plates. Sulfation has a negative impact on your battery's performance, leading to longer charging times, shorter run times between charges and a shorter overall lifespan.

Overcharging can be equally damaging. Applying too much current cooks the components inside your battery. This can cause the water in the electrolyte to break into oxygen and hydrogen, creating a buildup of flammable gasses that need to be vented. This loss of hydrogen and oxygen throws off the chemical composition of the electrolyte, making it far too acidic. Overcharging can also cause the battery's plates to corrode, harming the battery's performance and shortening its lifespan. If you overcharge a battery too much, you can kill it completely.

What are the Different Types of Battery Chargers?

Battery chargers are designed to work with a particular battery chemistry at a particular voltage in order to apply the correct amount of electrical current. That's why it's important to use a charger that matches your battery's chemistry and voltage. Keeping that in mind, there are essentially three basic types of battery chargers available for lead acid batteries: standard chargers, trickle chargers and battery maintainers.

  • Standard Chargers work by supplying a constant source of DC (direct current) electricity to a battery. Since they need to be shut off manually, it's important to monitor the charging process when using a standard charger. Otherwise, you could very easily undercharge or overcharge your battery.
  • Trickle Chargers are used to maintain batteries in applications that spend long periods in storage. They work by supplying your battery with a very low voltage that's designed to charge it slowly over a long period of time. Even though they apply very small amounts of current, it is still possible to overcharge a battery using a trickle charger if it remains attached for too long.
  • Battery Maintainers (also known as smart chargers) have electronic circuits inside them that can gauge how much power is stored in the battery. It uses this information to switch off the current and enter a float mode when the battery reaches its capacity. Unlike with standard and trickle chargers, a smart charger can stay connected to your battery indefinitely without fear of overcharging. This makes them the perfect fit for maintaining batteries over long periods of inactivity.

Find the Right Battery Charger at Batteries Plus

Visit Batteries Plus online or in-store for all of your charging needs. We carry battery chargers for cars and trucks, motorcycles, boats and so much more. If you want to know more about this topic, we have plenty of helpful articles in our online blog. Some related articles include "How Far Do I Need to Drive to Charge My Car Battery?" and "How Do Battery Charging Cycles Work?"

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