Battery regenerator
From Wikipedia, the free encyclopedia
A battery regenerator is a device that restores capacity to lead-acid batteries, extending their effective lifespan. They are also known as desulphators, reconditioners or pulse conditioning devices.[1]
When batteries are stored in an uncharged state for an extended period, lead-sulfur deposits form and harden on the lead plates inside the battery. This causes what is known as a "sulfated battery," which will no longer charge to its original capacity. Regenerators send pulses of electric current through the battery, which in some cases may cause the sulfate to flake off the plates and eventually dissolve.
Conventional lead–acid batteries consist of a number of plates of lead and lead dioxide suspended in a cell filled with weak sulfuric acid. Lead oxide reacts with the sulfur and oxygen in the acid to give up an electron, leaving the plate positively charged and producing lead sulfate. Lead reacts with the acid by taking in two electrons, leaving it negative while also producing lead sulfate. The two chemical processes continue as long as an external circuit is available to allow the electrons to flow back into the positive plates, but reaches equilibrium quickly when the battery is disconnected from the circuit. Each complete reaction produces about 2.11V. A typical 12V battery consists of six individual "cells" wired together in a single box, producing 12.66V when fully charged.
As a battery is discharged the density of lead sulfate in solution increases. In common designs, it reaches a critical density when discharged to about 75% depth of discharge, or below.[2] For instance, a 12V battery with a 100 ampere hour (Ah) capacity will reach this density when 25 Ah (300 Wh) or more have been drawn from the battery. At this point, the lead sulfate will begin to precipitate out of solution onto the battery plates, forming a spongy film. If the battery is immediately recharged, the film will dissolve back into the acid.[2]
If the battery is stored or repeatedly operated in this partially charged state for an extended period, the film will slowly crystallize into a solid. This process of "sulfation" takes time, so it only has a chance to build to significant levels if the battery is repeatedly discharged below this critical level. There are numerous other conditions that can lead to the same problem developing.[3]
Batteries also have a small amount of internal resistance that will discharge the battery even when it is disconnected. If a battery is left disconnected, any internal charge will drain away slowly and eventually reach the critical point. From then on the film will develop and thicken. This is the reason batteries will be found to charge poorly or not at all if left in storage for a long period of time.