Basically, it is a matter of thickness, and the quality of an insulator.
All lead acid cells work essentially the same: A lead oxide electrode immersed in sulfuric acid converts to lead sulfate when power is drawn from the cell. Lead sulfate is a very good insulator when it gets thick enough. So, as the cell discharges, a lead oxide layer builds on the plates. When the lead sulfate gets thick enough, it insulates the remaining lead oxide from the current flow, and the cell is discharged. When it comes time to recharge the cell, you apply voltage, and if the sulfate layer is still thin enough, current will be drawn, and electrolysis action will commence, and the lead sulfate will be turned back into lead oxide, and sulfuric acid. If you let the dead cell sit around before recharging it, the lead sulfate will have a chance to convert even more of the lead oxide to sulfate, and the layer will grow thicker, and thicker, and become a better and better electrical insulator.... To the point where the lead plates are completely isolated and no current can pass.... The cell is ruined. One way you can sometimes resurrect a cell in this ruined condition is to apply a high voltage, with a low current limit to the cell. This will get some current flowing, and will convert, albeit slowly, some sulfate back to lead oxide and sulfuric acid. Such repairs take weeks, or months, to work, and have a great risk of forming current hot spots which will physically destroy the plates. Others say that applying a stream of short, high voltage pulses, to the cell will break down the sulfate's insulation ability, and let the electrolysis action commence. Either method will work, somewhat. And only on a cell that isn't too far gone in the first place... eg. a cell that has only been dead for a week or two. -Chuck Harris Robert Roehrig wrote:
Anyone know why Gel Cell batteries go HI-Z if discharged below a certain level? Also is there a way to rejuvenate a "dead" one? _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
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