Technical Info
Negative Expanders For Lead-Acid Battery Applications
What's an Expander?
Technical Info-
A Division of...
What is an expander?
Expanders are additives to the negative plates of lead-acid batteries that increase the electrical capacity and the life. They increase the surface area of the active material, produce and maintain a fine-grained crystal structure and prevent passivation when the battery is discharged. They are added to the active material during paste mixing in
an amount that depends on the battery's application.
There are a great many different materials and formulas used to manufacture expanders but, generally, they all contain barium sulfate, carbon black and sodium lignosulfonate. Each of these materials performs a different but complimentary function to ensure that the negative plate has both outstanding capacity and life.
Barium sulfate has a very similar crystal structure to lead
sulfate and therefore provides sites for the precipitation of lead sulfate during discharge. The lead sulfate crystals
grow on the barium sulfate
thus preventing coating of the active material with a thin non-conducting film.
Carbon black, barium sulfate, sodium lignosulfonate, and others.
Increased surface area with 0.5% Vanisperse A.
Surface area with no organic.
Carbon, since it is a good conductor of electricity, improves the conductivity of the negative active material and aids in the formation of the plate. Sodium Lignosulfonate is very strongly adsorbed on the surface and produces microscopic lead particles. This giant molecule clings to the lead surface and prevents the microscopic lead particles from growing together
to form a hard solid mass.
It increases the surface area resulting in improved ampere-hour capacity. Batteries
that operate at very high discharge rates and at low temperatures use an expander with a high percentage of sodium lignosulfonate while those requiring moderate dischare rates but long cycle life use expander with a high proportion of barium sulfate.
