Samlex Solar SCC-30AB Owner's Manual page 9

Both the plates consist of a rectangular grid made out of alloyed Lead with
rectangular holes in it as shown in Fig 3.1 below:
Fig 3.1. Grid structure of Positive and Negative Plates in a Lead Acid Battery
The holes in the grid of the plates are filled with a paste of active material made out
of a mixture of Red Lead and 33% dilute Sulphuric Acid (different manufacturers
use modified mixtures). The paste is pressed into the holes in the grid. This paste
remains porous and allows the Sulphuric Acid in the electrolyte to react with the
lead inside the plate increasing the surface area many fold. At this stage, the Positive
and Negative plates are identical. Once dry, the plates are then stacked together
with suitable separators and inserted in the battery container. After the electrolyte
has been added to the cell, the cell is given its first "Forming Charge". During this
"Forming Charge", the Lead paste in the Positive plate gradually turns to Lead
Dioxide (chocolate brown color), and the Lead paste in the Negative plate turns to
Sponge Lead (slate gray color). Such charged cell is ready to be used.
The above grid structure of the plates is made from a Lead alloy. A pure Lead grid
structure is not strong enough by itself to stand vertically while supporting the active
material. Other metals in small quantities are alloyed with Lead for added strength
and improved electrical properties. The most commonly alloyed metals are Antimony,
Calcium, Tin, and Selenium.
The two most common alloys used today to harden the grid are Antimony and
Calcium. Batteries with these types of grids are sometimes called "Lead-Antimony"
and & "Lead-Calcium" batteries. Tin is added to Lead-Calcium grids to improve
cyclability
The major differences between batteries with Lead-Antimony and Lead-Calcium grids
are as follows:
• Lead-Antimony batteries can be deep cycled more times than Lead-Calcium batteries.
• Flooded Lead-Antimony batteries require more frequent maintenance as they near end-of-
life since they use an increasing amount of water and require periodic equalization charges.
GENERAL INFORMATION: BATTERIEs
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