Desulfation is the process of reversing the process of sulfation that occurs to a lead-acid battery

Lead-acid battery

Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, their ability to supply high surge currents means that the cells maintain a relatively large...

 over time. Desulfation restores, at least partially, the ability of the battery to hold a charge over the life of the battery originally caused by sulfation). Sulfation is the formation of large non-conductive crystals of lead(II) sulfate (PbSO4) on the battery plates. Eventually so much of the battery plate area is unable to supply current that the battery capacity is greatly reduced.

Desulfation is an attempt to reverse sulfation. Desulfation is achieved by high current pulses produced between the terminals of the battery. This technique, also called pulse conditioning, breaks down the sulfate crystals that are formed on the battery plates.

Sulfation is a natural process that occurs in all lead acid batteries, but can occur significantly faster if placed in the wrong combination of temperature, poor charging technique, protracted battery disuse, etc.

Desulfation Techniques

Temperature affects both the desulfation and sulfation by increasing the rate of change for each. For instance, a warmer temperature battery will desulfate or sulfate more quickly. There are limits and too much heat can damage a battery (See Permanent Damage below).

Circuit elements such as a timer, stimulator-amplifier device, and microcontrollers can be used to regulate the pulses of different widths and frequency of these high current pulses. These can also be used to automate the process since it takes a long period of time to desulfate a battery fully. Battery chargers designed for desulfating lead-acid batteries are commercially available.

Short high current pulses tend to work best.

Permanent Damage

A few unrecoverable battery symptoms include:

• Loss of lead material on plates
• Plates physically bent due to extreme temperatures and over charging

Recharged batteries which have a resting voltage under 8 Volts are highly suspect of being unrecoverable.

Symptoms

Batteries which have sat unused for long periods of time can be prime cadidates for desulfation. A long period of self-discharge allows the sulfate crystals to form and become very large. Some typical cases where lead acid batteries are not used frequently enough are planes, boats (esp sail boats), old cars, and home power systems with battery banks that are under utilized.

Batteries with noticeable sulfation might show signs of:

• high internal resistance
• low current supply

A white coating on the plates may be visible (in batteries with clear cases,or after dismantling the battery).

Prevention

Some charging techniques can aid in prevention such as equalization charging and cycles through discharging and charging regularly. It is recommended to follow battery manufacturer instructions for proper charging.

SLI vs Deep Cycle

SLI batteries (starting, lighting, ignition; i.e. car batteries) have less deterioration because they are used more frequently vs deep cycle batteries. Deep cycle batteries tend to require more desulfation, can suffer from overcharging, and can be in a very large bank which leads to unequal charging and discharging.

See also

• Sulfation
  Sulfation
  Sulfation in biochemistry is the enzyme-catalyzed addition of sulfate to another molecule. It often refers to a phase II enzyme reaction. This biotransformation process uses its cosubstrate 3'-phosphoadenosine-5'-phosphosulfate to transfer sulfate to a xenobiotic...
  
  
• Lead-acid battery
  Lead-acid battery
  Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, their ability to supply high surge currents means that the cells maintain a relatively large...
  
  
• Rechargeable battery
  Rechargeable battery
  A rechargeable battery or storage battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to...
  
  
• Battery recycling
  Battery recycling
  Battery recycling is a recycling activity that aims to reduce the number of batteries being disposed as municipal solid waste. Batteries contain a number of heavy metals and toxic chemicals, their dumping has raised concern over risks of soil contamination and water pollution.-Battery recycling by...
  
  
• Automotive battery
• VRLA battery
  VRLA battery
  A VRLA battery is a type of low-maintenance lead–acid rechargeable battery. Because of their construction, VRLA batteries do not require regular addition of water to the cells....