CLAIMS
1. A lead-acid battery for energy storage, comprising:
an electrode plate group; and
an electrolyte with which the electrode plate group is impregnated,
the electrode plate group including a plurality of negative electrodes, a plurality of positive electrodes, and a plurality of separators,
each negative electrodes including an negative electrode grid, and a negative electrode active material held by the negative electrode grid,
each positive electrode including a positive electrode grid, and a positive electrode active material held by the positive electrode grid, and
each separator separating the positive electrode from the negative electrode, wherein
a total pore volume of the positive electrode active material is 0.087-0.120 cm3/g, and
the negative electrode active material contains 3.2-4.8 mass % of barium sulfate.
2. The lead-acid battery of claim 1, wherein
the positive electrode active material includes a large number of pores having a pore size of 0.8 um.
3. The lead-acid battery of claim 2, wherein
a peak of a pore volume appears within a range of a pore size of 0.7-0.9 um in a graph of a differential curve of pore distribution obtained by measuring the positive electrode active material by mercury intrusion porosimetry.

4. The lead-acid battery of claim 1, wherein
the total pore volume of the positive electrode active material is 0.090-0.110 cm3/g.
5. The lead-acid battery of any one of claims 1 -4, wherein
the negative electrode active material contains 0.3-2.0 mass % of acetylene black.
6. The lead-acid battery of any one of claims 1-4, wherein
the negative electrode active material further contains 0.1-2.0 mass % of a lignin-based surfactant.
7. The lead-acid battery of any one of claims 1 -4, wherein
a weight ratio of the negative electrode active material to the positive electrode active material, that is, of the negative electrode active material/the positive electrode active material is 0.7-0.95.
8. The lead-acid battery of any one of claims 1-4, wherein at least the positive electrode grid is an expanded grid.
9. The lead-acid battery of any one of claims 1 -4, wherein
the separators are envelope separators made of hydrophilically treated synthetic
fibers and sheet separators made of glass fibers,
each positive electrode is accommodated in the envelope separator, and
each sheet separator is sandwiched between the envelope separator and the negative
electrode.

10. The lead-acid battery of claim 9, wherein
the synthetic fibers include at least acrylonitrile-based fine fibers having a diameter of0.5-2.0nm.
11. The lead-acid battery of claim 10, wherein
the synthetic fibers further include acrylonitrile-based coarse fibers having a diameter of 2.5-8.0 um.
12. The lead-acid battery of claim 11, wherein
a content of the acrylonitrile-based fine fibers is higher than a content of the acrylonitrile-based coarse fibers.