- Desulfation
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Desulfation is the process of reversing the process of sulfation that occurs to a lead-acid battery 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.
Contents
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
References
- Lead Acid Battery Desulfator (Home Power #77 June/July 2000) [1]
- Battery Plate Sulfation (MagnaLabs)[2]
- Battery Desulfation [3]
- Lead Acid Batteries [4]
- DC Supply! (April 2002) [5]
- Some Technical Details on Lead Acid Batteries [6]
External links
Categories:- Rechargeable batteries
- Battery (electricity)
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