Flooded Lead Acid Battery: a Full Introduction

Flooded Lead Acid Battery: a Full Introduction

You may know lead acid batteries, but what about flooded lead acid batteries? Here is a full introduction to flooded lead acid batteries.

Flooded lead acid batteries (sometimes called “wet cell” lead acid batteries) are the most common type of deep-cycle solar battery. They are the most affordable solar storage battery up front, have been in use for years, and are well understood.

In this blog, we’ll explore everything about flooded lead-acid batteries. Please keep reading.

There are other types of lead acid batteries, such as AGM batteries and Gel batteries.

What is a Flooded Lead Acid Battery?

For many years, the flooded lead-acid battery has been the standard in the solar industry. Golf carts and forklifts both utilize this kind of battery. They are the most cost-effective and longest-lasting of lead-acid batteries.

An electrolyte that can move freely inside the battery casing is present in flooded lead-acid batteries. Electricity is stored when the battery acid and lead plates react.

In order to prevent electrolyte leakage from the top caps, these batteries are designed to be mounted upright. (You can mount sealed lead acid batteries in any direction without worrying about leaks because they are sealed. Flooded batteries are not the same.)

Despite being the most affordable battery on the market, it will only function at its best if it is properly maintained. To ensure the longest lifespan possible, the levels must be checked monthly and topped off with distilled water.

Flooded Lead Acid Battery: a Full Introduction

Note that when charging, flooded lead-acid batteries release toxic hydrogen gas. To stop this gas from becoming trapped and posing a threat to the environment, it must be enclosed and vented to the outside.


  1. The most cost-effective Lead Acid battery.
  2. Compared to VRLA batteries, life is longer.
  3. robust and less temperature-sensitive than Sealed VRLA.


  1. twice monthly upkeep is required.
  2. Emits corrosive fumes.
  3. Needs acid proof battery room/enclosure
  4. It takes 55 to 90 hours to fully charge; it cannot be transported in that state.
  5. For handling extremely dangerous sulfuric acid, it is necessary to have people with special training.

How Do Flooded Lead Acid Batteries Work?

To start a chemical reaction, flooded batteries use a medium that contains liquid electrolytes. Battery acid bonds to the lead plates when the battery is connected. As a result, the attached circuit receives an electric current as a reaction.

Lead, lead oxide, and electrolyte undergo a chemical reaction when the battery terminals are coupled with the load. Due to this chemical process, electricity flows to the load through terminals, which in turn helps to remove sulfuric acid from the solution that is infused into the plates.

The bonds between the sulfuric acid and the battery’s plates are broken when the battery is being charged by a reverse current, allowing the acid to return to the solution and potentially produce more power for later use.

Flooded Lead Acid Battery: a Full Introduction

Do You Need to Add Water to Flooded Lead Acid Batteries?

Water is required by flooded batteries. The battery’s performance and longevity will suffer if watering is not done at the proper time and in the proper amount.

Always add water after the battery has finished charging. There should be enough water on the plates before charging. The water level should also be higher than the battery plates if the battery has been partially or fully discharged. After a full charge, keeping the water level where it should be will eliminate the need to worry about the water level at a different state of charge.

How Do You Maintain a Flooded Lead Acid Battery?

To operate properly, flooded lead-acid batteries need routine maintenance. To keep the battery bank in top shape, we advise checks every two to four weeks.

Add Distilled Water Every 2-4 Weeks

During the charge cycle, flooded lead-acid batteries lose water. To maintain their health and function, they must be regularly refilled with distilled water.

Note that you should only use distilled water. The battery chemistry is weakened by the small particles and contaminants that non-distilled water (such as tap water) introduces.

Every 15 to 30 days, check the water level and top it off as necessary. The local climate, change settings, and particular applications all affect your watering schedule. Keeping a log of how frequently your batteries need to be recharged may be helpful.

Flooded Lead Acid Battery: a Full Introduction
  1. Once the batteries are fully charged, check the water level.
  2. To check the water level, open the vent well.
  3. Just below the maximum water level line, add water. DO NOT overfill past this line. The location of the maximum water level line should be specified in the battery installation manual.

Check the Battery State of Charge (SoC)

To keep track of how fully charged your batteries are, use a refractometer. Your batteries’ specific gravity is determined by the refractometer. To determine your battery’s state of charge based on its specific gravity reading, refer to the charts provided by the manufacturer of your battery.

Equalization Charges

Batteries should be equalized occasionally to make sure each cell is equally charged. When a battery is imbalanced (reading a different voltage or specific gravity), or every 30 to 90 days, apply a controlled overcharge.

  1. Before beginning an equalized charge, check the level of the water.
  2. Turn off any loads.
  3. Set your charger to the Equalize voltage recommended in your battery manual.
  4. Launch the equalized charge. During this process, gassing and bubbling are typical.
  5. Put the charger away and measure the specific gravity every hour. Once the specific gravity starts to fall, the EQ process is finished.

Other Routine Flooded Lead-Acid Battery Maintenance

  • The battery cable connections should be tightened as necessary. Utilize insulated tools and wear gloves and eye protection.
  • In order to prevent corrosion, clean the terminal connections and cables. Apply with a wire brush after making a paste out of baking soda and distilled water. Cleansing residue should be rinsed off and dried with a cloth or paper towel.
  • To prevent creating a current pathway or electrical leakage across the top of the battery, keep the top of the batteries free of dust and debris.
Flooded Lead Acid Battery: a Full Introduction

What is the Difference Between a Flooded Lead-Acid Battery and a Sealed Lead-Acid Battery?

The issue of battery maintenance is the key distinction between the two types of batteries. Water must occasionally be added to flooded lead acid batteries, equalization must be done periodically, and the specific gravity of the electrolyte must occasionally be determined using a hydrometer.

A flooded battery can off-gas hydrogen under certain battery charging conditions, necessitating venting of the battery to let the fumes out. This is another distinguishing feature of flooded batteries. An important selling point for those who don’t want to deal with battery maintenance is the fact that sealed lead-acid batteries don’t need maintenance and don’t need venting, in stark contrast to flooded batteries.

A sealed lead-acid battery may not perform as well as its flooded counterpart due to the inability to maintain the battery, which is one potential drawback.

Aside from the maintenance aspect, the two types of batteries are similar in size, weight, performance, and efficiency. The maintenance factor is the biggest and most obvious difference when customers choose which battery type to buy, although there are some minor advantages and disadvantages between the two.

Here are other comparisons of batteries:

Conclusion: Flooded Lead Acid Battery

Flooded lead acid deep-cycle batteries have the lowest cost per amp-hour and cost per kWh cycle of all deep-cycle battery technologies, which is their main advantage for storing renewable energy.

Today’s flooded lead acid batteries are generally sealed, protecting users from extremely dangerous lead and sulfuric acid.

Further Reading:

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