Differences between Flooded and VRLA batteries
The main difference between VRLA or Sealed Lead Acid batteries and Flooded lead batteries is that the electrolyte in the VRLA batteries is immobilized. This can be achieved by using Absorbed Glass Mat separators or Gelled electrolyte which divides VRLA batteries into two subtypes – AGM and GEL.
VRLA stands for Valve Regulated Lead Acid. These batteries are designed so that during charging, oxygen from the positive plates is able to migrate to the negative plates where it is reduced to water. This process reduces water loss greatly but is not 100% efficient and when the internal pressure builds up the excess oxygen and hydrogen is vented out of the battery via vent or a valve.
Flooded batteries get their name because they contain an excess of electrolyte fluid so that the plates are completely submerged. Flooded batteries are one of the oldest sources of DC power. They must be filled with distilled water and regularly maintained in order to function properly. Despite the higher maintenance requirements, a high percent of US automotive applications are powered by these batteries. Though they were invented in the 1880’s,they still have a few advantages over valve-regulated batteries.
Advantages of Flooded Batteries
- Old and well understood technology
- More available worldwide
- Cheaper than Sealed Lead Acid batteries
Disadvantages of Flooded Batteries
- Acid spillage is possible. Battery acid can damage other internal components
- Water loss occurs over time, resulting in the need for regular maintenance and refilling
- More ventilation space is required around the battery
- Usually bulkier than SLA batteries
- Shipping is expensive and often restricted
- Must only be operated in upright position
One of the biggest complaints people had concerning Flooded batteries was the threat of electrolyte spillage. In fact, this concern was instrumental in the introduction of VRLA batteries.They require far less regular maintenance, and they pose no threat of spillage. Applications such as UPS and alarm systems typically utilize VRLA batteries. The main downsides of these batteries are their shorter life span and higher price compared to the Flooded type. Also VRLA batteries do not tolerate overcharging as it leads to a higher rate of internal buildup of gasses which the vents can not cope to remove. Overcharging leads to premature failure.
Advantages of VRLA batteries
- Virtually no threat of acid leakage
- Less required maintenance, because the batteries never have to be filled with water
- Consume less space
- Less required ventilation area
- Can be operated in any orientation
Disadvantages of VRLA batteries
- More expensive
- Shorter life span
- Do not tolerate overcharging
In the automotive industry, flooded batteries are expected to remain a major component, though VRLA batteries have been gradually replacing them in many areas due to their reduced maintenance costs and easier handling.