Features of VRLA Technology

There are additional advantages with recombination batteries. For example, topping up with water is not necessary over the whole life of the battery, and the battery can be designed to survive a 30-day short-circuit test and, after recharge, have virtually the same capacity as before the test. Due to a marked reduction in water decomposition, there is only a small release of hydrogen gas and a low rate of self-discharge. Many studies of VRLA batteries have been published in recent years some examples are given as Refs. [2-14] (see also Chapter 1). 

The two technologies, gel and AGM, have many similarities, but there are also some differences. For example, it is well known that for tall cells in a vertical position, only gel cells can be used otherwise, acid stratification caimot be avoided. There are some fairly tall AGM cells on the market, but these are intended for use only in a horizontal position in order to avoid the acid stratification problem. For short cells, both gel and AGM designs are possible without restriction on cell orientation. Often, AGM is used when high power is requested whereas gel is especially useful to achieve a long lifetime. 

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