Battery Design: Flat Plate Versus Tubular

The flat plate and tubular are the two types of UPS batteries that are available to the users these days. Companies such as American Power Conversion (APC) manufacture all sorts of UPS models, some with flat plate batteries and others with tubular batteries. Basically, it is the design of the positive plate that differentiates a flat plate battery from a tubular battery. The biggest difference is that the flat plate design comprises of a tough alloy grid, which contains a special compounded paste, while the tubular design comprises of parallel tubes that contain lead oxide. Learning how these two types of batteries are produced can help in understand the differences in their performance.

Flat Pasted Plate Batteries

A tough cast iron grid made of lead alloy that usually contains around three to six percent of antimony is used to produce a flat plate battery. A specially compounded mixture that contains lead oxide water, and sulfuric acid is used to paste the grids on an automatic machine. A process in which the active material is converted in the plate to the required composition is used to cure the plates once they have been pasted. As a result of this the paste sets to a hard mass similar to cement. The plates are very tough and striking them produces a ringing bell-like sound. Apart from being consistent, batteries made of flat plates possess the following traits:

– A flat plate battery performs excellently

– These batteries are quite long lasting

– These batteries are durable and tough

– The pasted material in the plates is also long lasting

– The plates in the battery also have a glass wrap over them

Tubular Batteries

The tubes in tubular batteries have a more complex design, and the manufacturing process used to produce them is quite different too. Firstly, the grid is produced, which comprises of a sequence of 15 parallel lead spines cast onto a bar or rods. Lead alloy containing six to ten percent antimony is used for fabricating the grid. A sequence of parallel porous glass fiber tubes is attached over the grid spines. A plastic fitting is knocked onto the ends once the tubes are filled. The lead oxides are then converted to lead sulfate by soaking the assembly in dilute sulfuric acid. Batteries made of tubular plates possess the following traits:

– A tubular battery performs decently, but not as efficiently as a flat panel battery

– Tubular batteries are as long lasting as flat-panel batteries.

– The active material and lead in these batteries do not last long

– Cell life is shortened due to sensitivity to active material shedding

– Plate area is significantly lost due to sensitivity to top bar breakage

– Spines can end up off center of the tube


While users do not pay much attention to their UPS battery, but flat plate and tubular batteries are significantly different from each other. From the mentioned facts, it is apparent that the flat plate design is more efficient, long-lasting and reliable. Nonetheless, companies like APC manufacture UPS models with both flat plate and tubular batteries.