Page 224 - Battery Reference Book

1818 Lead-acid secondary batteries
The problem has been partly solved with the In a recombination electrolyte battery the electrolyte
introduction of maintenance-free batteries, with their is completely absorbed in the plates and the highly
improved grid alloys and reduced gassing and water absorbent and very porous separators consisting, usu-
loss. The drawback with this type of battery is the ally, of glass microfilms, which are closely wrapped
extra head space required to provide a reservoir of around the plates and take up within its pores all
acid, enabling the battery to last 3-4 years. In addi- the liquid electrolyte. There is no electrolyte above or
tion, there is skill the possibility of corrosion from below the cell assembly as in a conventional battery.
acid spray. When the positive plates become charged and give
In a conventional battery the gasses 'bubble' to the off oxygen, the easiest path for the gas to take is
surface through the electrolyte-the easiest path to take. through the highly porous separators to the negative

-

+ ~ -

m*

Electrolyte ' Separator
(a) Conventional design
(flooded)

2.3

2.1
2.0
1.9-
0 40 80 120 160
Charge (%) Charge (%)
(c) No recombination (d) With recombination
Figure 18.4 Recombination technology in lead-acid batteries. In a conventional cell, oxygen from the positive plate rises to the top of
the electrolyte and is lost. In a cell utilizing recombination electrolyte (RE) technology, oxygen passes through the special separator to the
negative plate and, ultimately, back into the electrolyte (Courtesy of Yuasa)