Lead-acid battery

1. A lead-acid battery in which at least one electrode plate group formed such that a plurality of positive electrode plates and a plurality of negative electrode plates are stacked on each other with a separator being interposed between adjacent ones of the positive and negative electrode plates is housed in at least one cell chamber together with an electrolyte,

wherein each positive electrode plate includes:

a positive electrode grid made of lead or a lead alloy containing no antimony,

a positive electrode surface layer formed on a surface of the positive electrode grid and made of a lead alloy containing antimony, and

a positive electrode active material with which the positive electrode grid is filled and which is made of lead oxide,

each negative electrode plate includes:

a negative electrode grid made of lead or a lead alloy containing no antimony,

a negative electrode surface layer formed on a surface of the negative electrode grid and made of a lead alloy containing antimony, and

a negative electrode active material with which the negative electrode grid is filled and which is made of lead oxide,

an area PS of the positive electrode surface layer on the surface of the positive electrode grid is larger than an area NS of the negative electrode surface layer on the surface of the negative electrode grid,

NS/PS falls within a range of 0.3-0.8, and

the positive and negative electrode surface layers are made of a Pb—Sb based alloy containing antimony at a content of 1.0 to 5.0 mass %.

2. The lead-acid battery of claim 1 , wherein

the content of the antimony is higher in the negative electrode surface layer than in the positive electrode surface layer.

3. The lead-acid battery of claim 1 , wherein

strands of the positive electrode grid have no twist, and at least one strand of the negative electrode grid has twists.

4. A lead-acid battery in which at least one electrode plate group formed such that a plurality of positive electrode plates and a plurality of negative electrode plates are stacked on each other with a separator being interposed between adjacent ones of the positive and negative electrode plates is housed in at least one cell chamber together with an electrolyte,

wherein each positive electrode plate includes:

a positive electrode grid made of lead or a lead alloy containing no antimony, and

a positive electrode active material with which the positive electrode grid is filled and which is made of lead oxide,

each negative electrode plate includes:

a negative electrode grid made of lead or a lead alloy containing no antimony,

a surface layer formed on a surface of the negative electrode grid and made of a lead alloy containing antimony, and

a negative electrode active material with which the negative electrode grid is filled and which is made of lead oxide,

a mass ratio M S /M P falls within a range of 0.50 to 0.74, where M P represents a mass of the positive electrode active material per cell chamber, and M S represents a mass of sulfuric acid contained in the electrolyte, and

the surface layer is made of a Pb—Sb based alloy containing antimony at a content of 1.0 to 5.0 mass %.

5. The lead-acid battery of claim 4 , wherein

the mass ratio M S /M P falls within a range of 0.57 to 0.70.

6. The lead-acid battery of claim 4 , wherein

W/L falls within a range of 0.50 to 0.80, where L represents an inner dimension of the cell chamber in a stacking direction of the electrode plate group, and W represents a total thickness of the positive and negative electrode plates.

7. The lead-acid battery of claim 6 , wherein

the W/L falls within a range of 0.60 to 0.70.

8. The lead-acid battery of claim 4 , wherein

a density of the positive electrode active material falls within a range of 3.6 to 4.8 g/ml.

9. The lead-acid battery of claim 8 , wherein

the density of the positive electrode active material falls within a range of 3.9 to 4.5 g/ml.

10. The lead-acid battery of claim 4 , wherein

a total pore volume of the positive electrode active material falls within a range of 0.06 to 0.18 ml/g.

11. The lead-acid battery of claim 10 , wherein

the total pore volume of the positive electrode active material falls within a range of 0.09 to 0.15 ml/g.

12. The lead-acid battery of claim 4 , wherein

the positive electrode plates of the electrode plate group are connected together in parallel by an electrode-plate connection plate extending in a stacking direction of the positive electrode plates, and the negative electrode plates of the electrode plate group are connected together in parallel by an electrode-plate connection plate extending in a stacking direction of the negative electrode plates,

the electrode-plate connection plates of adjacent electrode plate groups are connected together in series through a connector connected to the electrode-plate connection plates of the adjacent electrode plate groups, and

the electrode-plate connection plates and the connector are made of a lead alloy containing no antimony and containing tin.

13. The lead-acid battery of claim 12 , wherein

each of the electrode-plate connection plates of the electrode plate groups arranged respectively at both ends of the lead-acid battery is connected to a corresponding one of external terminals through a corresponding one of poles, and

the poles are made of a lead alloy containing no antimony and containing tin.