VRLA batteries offer a number of advantages compared to conventional lead-acid batteries. So they can be cycled in a partial state of charge. But limitations have to be observed, e.g., the negative electrode cannot be recharged separately and thus lost capacity cannot be regained. Furthermore, hydrogen evolution and grid corrosion must be in certain balance. At a too high hydrogen evolution rate the negative electrode will suffer gradual discharge. This might cause problem in hybrid-vehicle applications because of the unavoidably strong polarization during recuperation of braking energy. (c) 2005 Elsevier B.V. All rights reserved.