Flooded batteries are so called because they contain an excess of electrolytic fluid so that the plates are completely submerged.
As the batteries discharge, the chemical reaction produces oxygen and hydrogen which are released from the batteries. As a result, the electrolytic fluid starts reducing. But it should never be allowed to fall below the top part of the plates, thus exposing them. If that happens, the plates will get damaged and their life will reduce considerably. That is why they have to be periodically filled with distilled water to maintain the electrolytic fluid level above the top part of the plates.
Because the batteries are flooded with electrolytic fluid, you have to use them in an upright position. Also, you have to transport them in ships; you can’t transport them by planes. Although flooded batteries require regular maintenance, they are the best in terms of price.
Advantages of flooded batteries are:
- Long proven history of use
- High discharge rate capability
- Perform better in hot climates
- Perform better than VRLA batteries when regularly in a partial state of discharge
- Lowest price of all the battery types
Disadvantages of flooded batteries are:
- Need to be periodically refilled with distilled water
- Produce gas when charged and so require ventilation
- Can only be used in an upright position
- Cannot be shipped by air
- Cannot be kept in the vicinity of any electrical equipment or any inflammable material
- May emit acid spray if overcharged abusively
- Higher self-discharge rate than VRLA batteries