Difference between flat plate battery & tubular battery
The life of a flat plate battery is lower when compared to a tubular battery. Flat plate battery can easily shed their active material over time. The lead wires in the flat plate electrode are more easily attacked by the acid over time causing grid corrosion which is a common mode of battery failure. Flat plate battery are usually used in starter applications like in an automotive battery. Where the battery needs to be deeply discharged, flat plate battery easily fail when compared to tubular batteries.
Why tubular plate battery is better than flat plate battery?
The main reason is the multi-tube bag gauntlet and increased surface area of the positive plate. Advanced multi-tube bag gauntlets are constructed of 100% polyester of high-tenacity, multifilament yarns that are impregnated with an acrylic resin system and fixed crosswise to the tubes. Gauntlets commonly called PT Bags have the following characteristics:
- High porosity
- Low electrical resistance
- A well-defined pore size that permits easy movement to the electrolyte, but at the same time reduces the active material shedding to a negligible amount
- Good mechanical resistance and elasticity – The gauntlet resists the high pressure that the active material produces during its cyclical expansion.
- The fabric holds the active material pressed to the lead spines ensuring stable performance.
- Mechanical resistance to abrasion during cell assembly reduces scraps and pollution
- Reduced release speed of antimony – The fabric keeping the active material all around the spines acts as a filter for the electrolyte, reducing the release speed of antimony from positive grids.
- In contrast, in pasted plates, there is almost no distance between grid wires and electrolyte
- Due to increased positive plate surface area, tubular batteries have 20% more electrical capacity than flat plate batteries of comparable size and weight.
- With less positive plate shedding, tubular batteries also provide up to a 30% longer service life than flat plate batteries
It is better to use tubular battery for deep cyclic applications like inverters & UPS. Flat plate battery is mainly used in SLI (Starter Lighting Ignition) applications. A flat plate delivers high cranking currents for a brief burst to start the engine, but cannot sustain a continuous load drawn from it. If flat plates are used for inverter applications the battery will have a very short life and die in a few months.
Tubular plates are robust and hence have a life of about 10 to 15 years in float operation. They are also suitable for cyclic duty and offer the highest cycle life.
The active material is contained in the annular space between the spine and the oxide-holder. This restricts the stress due to the volume changes occurring when the cells are cycled. The end of life is again due to the corrosion of the spines and loss of contact between the spines and the active material. However, the contact area between the spine and the active mass is reduced in such a construction and hence under heavy current drains, the higher current density results in local heating leading to rupture of tubes and crack in the corrosion layer.
Tubular plates are the choice for deep cyclic applications. Always prefer to buy tubular plate battery for applications like inverters and deep discharge applications like traction e rickshaw toto & electric vehicles.
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