This is a series of multiple steps
starting with materials if construction. These materials include plate,
separators, containers, covers, and other items. The steps in cell fabrication
vary by design and manufacturer. These steps always result in a completed
element stowed into a container to which a cover has been sealed as the end
product. Significant steps in the process are detailed
This is usually a positive plate
operation. Plates must be wrapped securely and all seals must be intact. If
the wrap is a U-fold of separator material, the plate must be centered
properly. By design, some cell types do not require plate
This operation consists of placing
plates and separators in the correct sequence. This can be a manual or
automated operation. Quality Control inspections should look for damaged
separators and plates and correct separator coverage above and around the
This operation prepares plate lugs for
proper fusion during the strap burning operation. It is not always a
requirement. When required, lugs should be brushed to bright metal. Any
applied flux or tin should be kept to a minimum thickness and not allowed to
flow onto the element.
Plate Lug to Strap Bonding
This can be done manually or by
automated process known as "cast-on."
Fixtures and dams are applied to element lugs.
The operator, using a burning flame (torch) or electric arc, melts the lugs
and adds metal as required into a continuous and homogenous strap or bus bar.
Operator technique is critical. Other critical factors include torch or arc
temperature, alignment of parts, and stirring of molten metal during the
melting and fusion stage.
- Post undercutting
- Visual standard for bonds
- Scorching of separators
- Lead run-downs
- Burning height
- Post alignment/height.
- Sectioning of bonds
- Chemical etching of bonds (usually after
This is an automated process to
produce a strap burn. The correctly stacked element it placed in a holding and
clamping fixture in the machine. Optionally, the lugs can be brushed and/or
fluxed/tinned. The secured element is inverted into a mold of molten lead. The
mold has the shape of the desired strap (and terminal if required). The lugs
melt and join with the molten lead. The mass is cooled, and the finished
"cast-on-strap" is produced.
Meniscus (preferably concave)
Visual standards (cracks, holes,
- Chemical etching.
This is the process of placing the
burned together element into its container. Care must be exercised not to
damage the element or components in this operation. Where required by design
or application, snugness of fit must be insured. Proper location of positive
and negative terminals is required. Some manufacturers perform a "short" test
on the element at this point using a high voltage supply and a current-flow
indicator like a buzzer, a lamp, or a meter.
When two or more elements are placed
into a multi-cell container, they must be properly connected. This is often
done by manually burning a lead intercell connector. In some designs, it is
done automatically in an operation called "thru-the-partition welding". Also.
mechanical connections using threaded posts, bolts, and connector bars can be
Container/Cover seals vary
significantly among manufacturers and designs. Two basic types are employed,
adhesive seals and heat seals. Adhesive seals c can be asphalt compound or as
complex as multi-component resin systems. Surfaces must be clean and properly
prepared. Component mix ratio (where applicable) must be precise.
Heat seals are almost always made in
automated equipment. It heats and melts the cover and container surfaces
involved in the seal and then precisely places them together while the plastic
is still softened.
Two basic types are available; a lead
post bonded to a lead insert in the cover and seals that employ O-rings,
gaskets, seal nuts, and adhesives. There are also designs that employ
combination of the basic types. Many variations exist and no attempt will be
made here to describe them.