Separators, batteries, battery strings with improved performance, and related methods

A battery string comprising:

• four or more monoblock valve regulated lead-acid (VRLA) batteries wired in series, wherein a total voltage of the battery string is 48 volts or greater;
• each VRLA monoblock battery comprises
• an alternating sequence of positive and negative electrodes, and
• a separator disposed between each of the positive and negative electrodes, the separator consists of a microporous polyolefin layer including a surfactant sandwiched between a first absorptive glass mat and a second absorptive glass mat, wherein the first absorptive glass mat has a thickness from 1.0 to 3.3 mm and the second absorptive glass mat has a thickness of 0.6 mm, wherein the microporous polyolefin layer is a polyethylene layer with a ribbed or embossed backweb, a backweb thickness of the microporous polyolefin layer not including the thickness of the ribs or embossments is from 0.05 mm to 0.25 mm, and the microporous polyolefin layer with the ribbed or embossed backweb of the separator has a bi-modal pore size distribution consisting of a first region of pores consisting of larger pores having a size of 1 to 6 microns and a second region of pores consisting of smaller pores having a size of less than 0.9 micron, wherein 90% of the pores are smaller pores.