Why Batteries Fail

Lead Acid batteries were first developed more than 150 years ago with few changes made to the basic design since then. It is widely assumed that given the age of this technology, there is no room for further improvement. This is wrong. The performance, reliability, and length of service of the lead acid battery can be significantly improved by protecting it from the two primary causes of failure: lead sulfate crystalization (“Sulfation”) and lead shedding. Both of these processes are accelerated by the following conditions:

• Deep cycling – discharging a battery by 80% or more.
• Storing in a discharged state – when a battery is not promptly restored to a near fully charged state after use, or is not routinely top-off charged to offset natural self-discharge.
• Extreme high / low temperatures – lead acid batteries are designed to operate at 25OC and will degrade rapidly above 50OC and may be permanently damaged below -40OC.
• Overcharging – high voltage/current charging or “fast charging” can cause gasification and depletion of the electrolyte.
• Stratification of electrolyte – when a battery is idle for long periods, the heavier sulfuric acid separates from the lighter water in the electrolyte and forms a highly concentrated lower layer at the bottom of the battery leading to overcharging and corrosion of the electrodes.

Many lead acid batteries are removed from service long before reaching the manufacturer’s rated number of cycles. Even when achieving the manufacturer’s rated lifetime, most batteries still contain active material sufficient to operate for many more cycles.

The cause of battery failure is NOT the depletion of active material. Instead, the most common root cause of premature lead acid battery failure is “Sulfation” and the degenerative processes caused by it. The proper prevention of Sulfation can “extend” the life of most lead acid batteries by 2-5x that of an unmaintained battery.

ReBatt offers the most robust, comprehensive, and field-tested suite of lead acid battery maintenance products and processes available.

What is “Sulfation”?

Lead Acid batteries discharge and recharge through the electrochemical process:

Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l)

1. Sulfur (S) comes out of the electrolyte (H2SO4) and combines with lead (negative electrode, Pb) and lead oxide (positive electrode, PbO2) to form lead sulfate (PbSO4) during the battery DISCHARGE phase.
2. Sulfur (S) comes out of lead sulfate (PbSO4) to form the electrolyte during the battery RECHARGE phase.
3. When a battery is discharged more than 50% and then recharged fully, it completes one “cycle”.
4. During each cycle, a small amount of Sulfur (S) is left in lead sulfate (PbSO4) form, unable to return to the electrolyte (H2SO4). Over time, this residual lead sulfate hardens in to crystals. These crystals continue to grow, further trapping Sulfur in the lead sulfate and depleting the electrolyte. This process is called “Sulfation.” The images below are of actual lead electrodes magnified 400x from lead acid batteries that have been fully discharged. The image on the left is from a battery in good working condition, while the battery on the right is from a battery with severe Sulfation.

5. The original amount and strength of the electrolyte determines the amount of power the battery can store when fully charged. As Sulfur is depleted from the electrolyte through the process of lead sulfate crystallization (“Sulfation”), the fully charged capacity of the battery is reduced. The battery used to take the picture in the above, right has less than fifty percent of its original capacity.
6. Sulfation also reduces the efficiency of lead acid batteries by increasing their internal resistance making them harder to discharge and recharge.
7. Sulfation also contributes to other, irreversible causes of battery failure such as lead shedding, electrode warping, and electrolyte gassification.
8. Sulfation can be prevented and even reversed using ReBatt battery maintenance systems and processes.

What is “Sulfation”? - cont

What is Lead Shedding?

The lead electrodes corrode and deteriorate through the electrochemical process of discharging and recharging. Over-charging, high power/fast charging, gasification, and sulfation can accelerate this process, known as “lead shedding.” These effects can greatly shorten the time before the lead electrodes become spent, rendering the battery “dead.” The pace of lead shedding determines the ultimate life of any lead acid battery, and it can not be eliminated but it can be slowed. High power recharging accelerates lead shedding. It also causes gasification of the electrolyte, contributing to lead corrosions and further shortening the life of the battery. The formation of large lead sulfate crystals through sulfation place mechanical stress on the lead plate from within, also contributing to accelerated lead shedding. Lead shedding is further exacerbated by electrolyte stratification that occurs when a battery is left idle for long periods (even if fully charged.) The increased concentration of sulfuric acid caused by gravity pooling the sulfur at the bottom of the battery creates conditions in which Sulfation occurs more rapidly causing the lead plates to corrode in this region.

ReBatt battery maintenance systems and processes prevent Sulfation and counteract electrolyte stratification, delaying the onset of lead shedding and extending the useful life of batteries.

Pulse Technology

ReBatt battery maintenance systems rely on a patented electrical pulse charging technology that has been proven to prevent and reverse lead Sulfation over more than twenty years of commercial applications. Lead sulfate crystals of various sizes commonly found in lead acid batteries are stimulated over a specific range of resonant frequencies. This range of frequencies is produced in all of our battery maintenance recovery products as a discrete packet of electrical pulses delivered according to a patented algorithm that has been optimized to erode lead sulfate crystals. This core technology is combined with sophisticated electronics that charges and maintains lead acid batteries in near new condition long after untended batteries would see the end of useful life.

Above are actual pictures of lead electrodes removed from batteries tested under lab conditions. The top row of electrodes are taken from batteries charged and maintained using the patented pulse technology. The bottom row of electrodes are taken from batteries charged using an ordinary 3-phase rectifier. Throughout the test, the batteries installed with the pulse charger remained in near new condition far beyond the 480 cycles, while the conventionally charged batteries showed a significant decline in capacity after 100 cycles followed by a rapid decline and failure before reaching 200 cycles.

All ReBatt products are built around the core, patented pulse maintaining technology ensuring the best protection of lead acid batteries for optimal efficiency and longer life.