Comparison of VLA batteries in tubular and flat plate design
The earliest commercially successful positive plate was the Planté plate, where the active mass is formed by a corrosion process out of the pure lead grid. This type is phasing out now, because it needs 80 – 110% more lead for the same capacity and more costly production procedures than flat, or tubular plate type batteries. The flat plate type, invented in 1881 by Faure and Volckmar, has a far better lead utilization and is used now in all lead acid batteries for the negative plates and in the majority also for the positive plates.
We have chosen two pairs of flat and tubular cells of large capacity (1350Ah) and low capacity (310Ah). Each pair has the same dimensions. The flat plate battery is typically 15% heavier than the tubular. It has 50 to 100% more plates, which are thinner than the tubular plates. Consequently, the flat plate battery bears higher costs. The inner resistance is nearly half for the flat plate cells. It remarkably improves the high power discharges in the region from 10 min. to 30 min.
We try to give here proposals to application engineers as to which battery type fits best to customer requirements, based on the information presented in this paper.
For electrical systems of a very high safety level, like utilities, bank data centers, military or security applications, the VLA types have advantages versus the VRLA types. Visual inspection and gravity readings give more safety. For bridging times or peak current requirements of 60min or shorter, the VLA flat plate batteries provide a better power-per $ ratio. For bridging times of more than 60 min, the VLA tubular is the preferred choice.
In systems where the advantages of VRLA systems count, we see the AGM type in front for UPS applications, as far as bridging times of 60 min and lower are required and where life time expectations are limited, because the technical innovation requires a new power supply in the next 5 to 10 years anyway. If the electrical system has an expected usage of 10 to 20 years, VRLA GEL batteries should be preferred: VRLA GEL tubular plate batteries for discharge times of 60 min and longer and VRLA GEL flat plate batteries for 30min and shorter. For solar applications, maintenance-free batteries with very high cycle life are required. Here, the VRLA tubular GEL is the best choice.