6.1 Lead-Acid Batteries
111
VRLA battery, consisting of three to four 12 V modules with a total voltage of 36
or 48 V, and the capacity is 10–20 A h. It is a valve-regulated lead-acid (VRLA)
battery made up of two parallel-connected strings of 75–12.5 V modules connected
in series. Electromechanical relays are used to interconnect lower voltage modules
into a single battery when operational. The relays also double as an operational
safety that isolates modules in the event of improper battery operation. Control of
these relays in fault isolation conditions is non-trivial.
Valve-controlled sealed lead-acid batteries are new types of lead-acid batteries.
They use the “lean liquid” design. The glass fiber is used as a separator. The sulfuric
acid electrolyte is completely absorbed by the glass fiber membrane. There is no free
acid in the interior. The electrolyte in lead-acid batteries is gel-like, and there are
no free electrolytes inside the battery. Electrolytes that cannot move freely greatly
reduce the risk of lead-acid batteries during use.
Since the end of the 1970s, a fully closed lead-acid battery has been developed
internationally, which is divided into air tight and full density type. The battery has
the advantages of maintenance free, no pollution, and low price. There are three ways
to make the battery air tight.
(1) gas phase catalysis: with the palladium catalyzed Ambrose catalyst installed in
the battery cover, the electrode on precipitation of hydrogen and oxygen and
recombine into water, and returned to the inside of the storage battery, thereby
reducing water loss, reach maintenance free.
(2) auxiliary electrode type: a pair of auxiliary electrodes that absorb hydrogen and
oxygen in the battery or an auxiliary electrode containing only one hydrogen
in the battery. When the hydrogen generated by the battery is adsorbed on the
hydrogen auxiliary electrode, it forms a hydrogen electrode. It forms a selfdischarge small battery with PbO 2 , which reacts 2H 2 + PbO 2 + H 2 SO 4 =
PbSO 4 + 2H 2 O, and the water returns to the battery.
(3) the cathode absorption mode: the oxygen generated by the positive electrode
when it is charged, diffused through the diaphragm to the negative electrode,
reacts with the lead of active substances, forms PbO 2 , and then reacts with
H 2 SO 4 to generate PbSO 4 and H 2 O.
The cathodic absorption battery can use the appropriate diaphragm to make the
battery limit liquid or lean liquid, or use colloidal electrolyte (SiO 2 silica powder
and a certain amount of H 2 SO 4 to form silica gel). It can make electrolyte fixed,
and no gas escapes, to achieve the requirement of full sealing. But considering the
self-discharge of the battery and the possibility of hydrogen precipitation in the later
period of charging, the battery is equipped with a safety valve. When the air pressure
in the battery increases to a certain value, the gas is discharged, so it is also called a
valve-controlled closed lead battery.
Sealed maintenance free lead-acid batteries have all the advantages of open leadacid batteries. The so-called maintenance free is the relatively open battery that
needs regular water addition. The whole storage battery is totally enclosed (the
redox reaction of the battery is carried out inside the closed enclosure), so there
is no “harmful gas” overflow in the battery. No need to add water and other daily
111
VRLA battery, consisting of three to four 12 V modules with a total voltage of 36
or 48 V, and the capacity is 10–20 A h. It is a valve-regulated lead-acid (VRLA)
battery made up of two parallel-connected strings of 75–12.5 V modules connected
in series. Electromechanical relays are used to interconnect lower voltage modules
into a single battery when operational. The relays also double as an operational
safety that isolates modules in the event of improper battery operation. Control of
these relays in fault isolation conditions is non-trivial.
Valve-controlled sealed lead-acid batteries are new types of lead-acid batteries.
They use the “lean liquid” design. The glass fiber is used as a separator. The sulfuric
acid electrolyte is completely absorbed by the glass fiber membrane. There is no free
acid in the interior. The electrolyte in lead-acid batteries is gel-like, and there are
no free electrolytes inside the battery. Electrolytes that cannot move freely greatly
reduce the risk of lead-acid batteries during use.
Since the end of the 1970s, a fully closed lead-acid battery has been developed
internationally, which is divided into air tight and full density type. The battery has
the advantages of maintenance free, no pollution, and low price. There are three ways
to make the battery air tight.
(1) gas phase catalysis: with the palladium catalyzed Ambrose catalyst installed in
the battery cover, the electrode on precipitation of hydrogen and oxygen and
recombine into water, and returned to the inside of the storage battery, thereby
reducing water loss, reach maintenance free.
(2) auxiliary electrode type: a pair of auxiliary electrodes that absorb hydrogen and
oxygen in the battery or an auxiliary electrode containing only one hydrogen
in the battery. When the hydrogen generated by the battery is adsorbed on the
hydrogen auxiliary electrode, it forms a hydrogen electrode. It forms a selfdischarge small battery with PbO 2 , which reacts 2H 2 + PbO 2 + H 2 SO 4 =
PbSO 4 + 2H 2 O, and the water returns to the battery.
(3) the cathode absorption mode: the oxygen generated by the positive electrode
when it is charged, diffused through the diaphragm to the negative electrode,
reacts with the lead of active substances, forms PbO 2 , and then reacts with
H 2 SO 4 to generate PbSO 4 and H 2 O.
The cathodic absorption battery can use the appropriate diaphragm to make the
battery limit liquid or lean liquid, or use colloidal electrolyte (SiO 2 silica powder
and a certain amount of H 2 SO 4 to form silica gel). It can make electrolyte fixed,
and no gas escapes, to achieve the requirement of full sealing. But considering the
self-discharge of the battery and the possibility of hydrogen precipitation in the later
period of charging, the battery is equipped with a safety valve. When the air pressure
in the battery increases to a certain value, the gas is discharged, so it is also called a
valve-controlled closed lead battery.
Sealed maintenance free lead-acid batteries have all the advantages of open leadacid batteries. The so-called maintenance free is the relatively open battery that
needs regular water addition. The whole storage battery is totally enclosed (the
redox reaction of the battery is carried out inside the closed enclosure), so there
is no “harmful gas” overflow in the battery. No need to add water and other daily