User manual

Higher currents than those shown in the table may be
maintained for durations shorter than one minute. The
ability of the cell or monobloc to maintain higher currents
is dependent on the magnitude of the current, its duration,
the frequency of its application and, most importantly, on
the ability of the terminal connection to act as a heat sink
and dissipate the heat generated. For high rate applications
we strongly recommend testing under actual or simulated
application conditions.
Table 3-1
CYCLON
®
Battery Type Max. amps to 1.50 VPC
D single cell (2.5Ah) 65
Tall D single cell (4.5Ah) 65
D monobloc (2.5Ah) 50
X single cell (5.0Ah) 65
E single cell (8.0Ah) 65
X monobloc (5.0Ah) 50
E monobloc (8.0Ah) 50
J single cell (12.0Ah) 100
BC single cell (25.0Ah) 250
3.3 Low Temperature Operation
Exceptional low temperature characteristics are maintained
through the use of a separator system that minimises
resistance and diffusion effects. This feature, combined with a
large plate surface area, results in efficient utilisation of active
materials and excellent voltage regulation.
Because the cell operates as a "starved" electrolyte system,
there is only enough electrolyte to maintain the rated capacity
of the cell. The capacity available at low temperatures is a
function of both temperature and discharge current.
Figure 3-1 shows another reason why CYCLON
®
battery cells
have good discharge performance at low temperatures.
Figure 3-1: Internal Resistance Vs. Temperature
As the temperature drops, the increase in internal resistance
is relatively gradual down to a little under 0°C (32°F). This
also explains why CYCLON battery cells have excellent low
temperature performance.
3.4 Position Flexibility
With the starved electrolyte system, the sulphuric acid
is absorbed within the cell plates and the glass mat separator.
The cell is virtually dry with no free electrolyte, allowing it
to be charged, discharged or stored in any position without
electrolyte leakage.
3.5 Recombinant VRLA Design
One of the most important features of the CYCLON battery
design is its recombinant valve regulated lead-acid (VRLA)
design. This mode of operation is possible because the cell is
able to use the oxygen cycle during overcharge. The oxygen,
evolved at the positive electrode when the cell is overcharged,
is recombined at the negative electrode. A self-resealing valve
is provided as a safety vent in case of misapplication or other
abuse of the cell that would cause the internal cell pressure to
increase.
In CYCLON batteries, water loss is greatly reduced due to two
design features. First, because water tends to decompose
around impurities in the lead, the rate of such decomposition
is reduced due to the high purity of the lead used in CYCLON
batteries. Second, the use of high pressure seals contains the
gases within the cell, promoting more efficient recombination.
In a conventional lead-acid cell, the charge current
electrolyses the water to produce hydrogen from the negative
electrode and oxygen from the positive electrode. Thus water
is lost from the cell, and it must be replenished by means of
frequent topping up with water.
The evolution of the two gases does not occur at the same
time due to the fact that the recharge efficiency of the positive
electrode is less than that of the negative electrode. This
means that oxygen is evolved from the positive plate before
the negative plate can generate hydrogen.
As oxygen is evolved from the positive plate, a significant
quantity of highly active spongy lead exists on the negative
electrode before the negative plate can generate hydrogen.
If the oxygen that is generated by the positive plate can be
transported to the negative plate, the spongy lead will react
rapidly with the oxygen to form lead oxide as shown by the
following reaction:
2Pb + O
2 ➔ 2PbO (Eqn. 1)
0
100
200
300
400
500
-4 -30 -20 -10 0 10 20 30 40
Temperature, ºC
lanimon % ,ecnatsiser .tnI
8
Publication No: EN-CYC-AM-007 - December 2008
www.enersys-emea.com