Photovoltaic Power Generation - Renewable Energy: Technology, Economics and Environment - page 272

solubility of lead sulphate) are changed. The electrical behaviour of a lead-acid
battery deteriorates with increased depth of discharge.

+

- Lead grid

Porous
separator

Porous PbO 2
active mass

Electrolyte
(diluted
sulfuric acid)

Porous
spongy lead
(active mass)

Fig. 6.21 Scheme of a lead-acid battery

Discharg e

⎯⎯⎯⎯→

PbO Pb 2H SO ++ 2PbSO 2H O +

2 2 4 4 2

←⎯⎯ ⎯ (6.3)

Charg e

There is a great variety of different designs of lead-acid batteries available on
the market. It can be distinguished between batteries designed for high capacities
(such as starter batteries for motor vehicles), batteries for a long technical lifetime
and few cycles (mainly for uninterrupted power supplies) and batteries designed
for strong cyclic operation (e.g. for electrically powered vehicles, fork lifts or
wheelchairs). According to the respective requirements, different electrode de-
signs and geometry are used. The main difference can be seen between "flat plate
electrode" and "tubular plate electrode", illustrated in Fig. 6.22. Recently also
batteries with wound electrodes are available. They show in some application
areas very promising results.

Fig. 6.22 Suitable electrode types for photovoltaic batteries (left: flat plate electrode, right:
tubular plate electrode)