Flooded lead acid batteries

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Flooded Lead Acid Batteries

Flooded lead acid batteries or FLA batteries are one of the oldest technologies on the market, but are still widely used. They are called so because of the liquid electrolyte which is free to move within the cell. Flooded lead acid batteries are usually the cheapest, but demand a lot of attention and constant maintenance. The thing is that the liquid isn’t sealed, which means batteries dry out from time to time.

Anatomy of flooded lead acid battery

Flooded battery has some main components:

  • Positive and negative plates;
  • Separator, which doesn’t allow the two plates touch each other;
  • Electrolyte (water and sulphuric acid).

They are enclosed in a plastic cell which keeps the electrolyte in. When the battery discharges, lead and lead dioxide react with sulfuric acid in the electrolyte to form lead sulfate. When the battery recharges, lead sulfate reverts back to lead, lead dioxide, and sulfuric acid.

How to size FLA battery for solar PV system

When sizing your battery, think about how you’re going to use it. For example, if you just need a backup in case of power outage, you should calculate your daily energy consumption first. There are several ways you can do that: check the electrical meters, look at your recent electricity bills or count the power ratings of all your household appliances.

When choosing flooded lead acid batteries, take into account their depth of discharge (DOD) — solar batteries should not be discharged below a certain level on a regular basis. For flooded batteries it is just 50%, which means you can’t discharge more than a half of the battery on a regular basis. Remember, constant deep discharge leads to an early death of a battery.

Pros and cons of flooded lead acid batteries


  • Low cost for the storage capacity
  • Support high rates of charge and discharge
  • The most resistant to damage if overcharged


  • A relatively short lifespan (3-5 years)
  • It takes from several hours to a day to charge a battery
  • To ensure proper functioning, plates of every cell in the battery must be submerged in water (hence the name ‘flooded’), so the water level must be monitored every 1 to 3 months
  • The hydrogen gas they release when charging is explosive, so they must be in a well-ventilated area (not in living space) and kept away from fire
  • Classified as a dangerous good

Find FLA batteries for your needs at A1SolarStore

  • Our warehouses are located on both east and west coasts of the USA: California, Washington, Colorado, Texas, Florida, New Jersey, and Missouri
  • We process all orders within 24 hours and ship them within 48 hours
  • Delivery normally takes between 4-7 business days
  • All of our suppliers are trusted solar panel manufacturers

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