VRLA-AGM Valve Regulated Sealed Lead Acid Battery Principles
Valve Regulated Lead Acid, abbreviated as VRLA, is known in Chinese as valve regulated sealed lead acid battery. Although it belongs to the lead acid family, its construction is completely different from traditional open-vented batteries: under normal operating conditions the battery remains sealed, and the gas generated internally recombines at the negative electrode via the Absorbent Glass Mat (AGM). Only when pressure exceeds the normal range does the safety valve open and release gas, giving it three major characteristics: maintenance-free, rechargeable, and leak-proof. CSB is a globally leading manufacturer of valve regulated lead acid batteries, with products sold to more than 100 countries and regions, and its entire VRLA product line is built on this technical approach.
The key function of the AGM is to provide a channel for oxygen, allowing it to pass through the separator from the positive electrode to the negative electrode and recombine into water; official data shows the recombination rate can reach 99%. Relying on this mechanism, electrolyte loss is greatly reduced, and the battery does not need watering during its service life. Complementing this are pure lead grid construction and proprietary formulations—the grid both conducts electricity and supports the active material, and the pure lead system helps slow corrosion, thereby supporting a longer float standby life. For this reason, VRLA-AGM batteries are widely used in backup power scenarios that require long-term online operation and low maintenance frequency.
In terms of electrical parameters, the nominal condition for VRLA-AGM is 25°C (77°F). Taking a 12V battery as an example, the float charge voltage falls between 13.5-13.8 Vdc, while the equalization charge voltage is between 14.4-15.0 Vdc; actual values vary by model and cell construction. Design life is likewise stated under float standby conditions at 25°C, ranging from 5 years to 20 years, with some series additionally marked with Eurobat (20°C) classification. Regarding temperature range, the nominal is 25°C, the discharge range is -15°C~50°C, some series can reach -25°C~50°C, and the charge and storage range is -15°C~40°C; these specifications directly affect capacity correction and life expectancy during the selection stage.
In terms of product system, CSB currently sells 142 models across 20 series, with voltage levels including 2V cells, 6V, 12V, and 512V lithium battery cabinets, capacity types covering 4.5Ah to 1700Ah, and high-rate types covering 18W to 9000W (5–15 minute rate). The VRLA-AGM series is segmented by application scenario: the data center UPS field includes HR, HRL, XHRL, XPL, XHT, etc.; the telecom field includes MSJ, MSV, MU, TPL, XTV, etc.; the renewable energy field includes RE, XTV-WT, etc.; general purpose includes GP, GPL; and the electric mobility field includes EVX, EVH. Each series differs in emphasis on terminal type, front or top access, cycle life, and high-temperature tolerance.
Understanding how VRLA-AGM works is very helpful for proper use and maintenance. Gas recombination effectiveness depends on appropriate charge voltage and temperature environment: overcharging or high temperature accelerates water loss and grid corrosion, while undercharging causes sulfation, and both conditions will reduce actual life. Therefore, in actual projects, charger settings should refer to the float and equalization charge ranges given in the model data, while evaluating the design life specification in conjunction with ambient temperature. CSB model data also lists referenced standards such as IEC 61056, IEC 60896, IEC 60254, IEC 61427, and UL1989 Recognized, which can be used for technical reference.
