3
www.enersys-emea.com
CHARGING
FLOAT CHARGING (Preferred Method)
For maximum service life, DataSafe
®
MX batteries should be float charged
using a well regulated constant voltage.
CONSTANT VOLTAGE CHARGING (Recommended Charging Method)
Constant voltage charging is the most efficient and safest method of
charging a sealed lead acid cell. There are two methods of constant voltage
charging, float and fast.
1. FLOAT CHARGING
This type of charging is to be used in standby applications.
Note: For the battery to attain 100% capacity whilst being charged at
2.27 Vpc @ 20°C a minimum of 7 days recharge time is required.
Voltage Setting
When the DataSafe MX battery valve regulated cell is to be float charged in
a standby application, the constant voltage charger should be maintained at
2.27 Volts per cell whilst at an ambient temperature of 20°C for maximum
float life.
Temperature excursions away from this will cause a reduction in life for
high temperatures or a reduction in capacity due to undercharge at lower
temperatures. The general rule is that for every 10°C rise in temperature
there is a 50% reduction in the float life of the product.
Current Setting
There is no upper limit setting to the current requirements during constant
potential charging as the battery itself will regulate the current only
accepting as much as is required to reach its fully charged condition.
It should however be noted that the higher the charge current available
from the charging source, the quicker the battery will recharge.
In a fully charged float condition, at 20°C, DataSafe MX batteries will draw
between 5 and 50 milli-amps from the charger.
2. FAST CHARGING
2.1 CONSTANT VOLTAGE FAST CHARGING
In order to facilitate more rapid charging of the DataSafe MX battery, it is
possible to use the ‘fast’ charge technique, ideally suited to more cyclic
applications.
Voltage Setting
For applications requiring a faster recharge, a potential of 2.4 Volts per cell
at 20°C can be applied across the battery terminals. This will facilitate a
more rapid recharge although due to this higher potential it is
recommended that this level is maintained only until the current being
drawn by the battery has remained level for a period of 2 hours. Should this
recharge potential be applied for extended periods the battery might
become warm thus accelerating grid corrosion and reducing the service life
of the product.
Current Setting
As with float charging, the greater the current available from the charging
source the faster the recharge will be, with no limit being placed on that
charging current. However at these elevated voltages, the final stabilised
current being drawn from the charger as the battery reaches its full state of
charge will be higher than the values attained at 2.27 Volts per cell.
INSTALLATION
TOOLS AND MATERIALS REQUIRED
Insulated torque wrench.
See monobloc details in this section for the correct settings.
In adverse conditions, terminal grease, consisting of 20% lanolin in
petroleum jelly, can be used to protect the terminal against external
corrosive substances.
Whilst not harmful to the battery, silicone grease should not be used as this
can interfere with other electronic components.
MONOBLOC DETAILS
The following information is very important in optimising the operation of
the DataSafe MX battery:
To allow an even air flow around the monoblocs, and thereby improve the
dissipation of the small amount of generated heat, it is recommended, but
not essential, that an air gap of approximately 5mm is left between the
monoblocs.
Ensure that the correct torque setting of 3.9Nm or 2.9 lb ft is applied to the
terminal nuts.
Please Note: Over-tightening may result in damage to the
terminal.
When supplied with EnerSys
®
standard connectors, terminal shrouds are
already fitted. After the terminal nut is torqued down the shroud can be slid
over the terminal. The shroud is flexible, allowing a voltmeter probe tip to
be applied to the terminal.
It is good practice to assemble large batteries in sections, leaving out
connectors at, 48V intervals, so reducing the danger during the main part of
the installation. When the rest of the installation has been checked carefully,
the remaining connectors can be fitted.
Rack and cabinets should normally be filled starting from the bottom, thus
ensuring stability throughout the installation.
Where parallel strings of monoblocs are being used, strings should
normally be arranged on racks or cubicles so that there is thermal balance
within each string. In other words; three strings on a three row rack should
be arranged such that each string is spread across the three tiers.
Total lengths of cable/connector runs should be the same in each string
until the strings are combined at a transition box or circuit breaker.
Monobloc numbers, when provided, can be affixed to any part of the
monobloc plastic case EXCEPT over the vent disc(s) for future identification.
SITE ACCEPTANCE TESTS
OPERATION
A site acceptance test, consisting of a fully loaded discharge for the
required autonomy time, should be performed approximately 7 days after
installation and commissioning. EnerSys can give recommendations for
each application.
The following tables show the effect of battery temperature on the electrical
discharge performance at different discharge rates. Performance is given as
a percentage of the performance at 20°C.
TEMPERATURE
Rate
0°C
5°C
10°C
15°C
20°C
25°C
30°C
35°C
40°C
5m
67%
76%
85%
92%
100% 108%
116%
125% 133%
10m
73%
80%
86%
93%
100% 107%
113%
119% 125%
15m
74%
81%
87%
94%
100% 106%
111%
116% 121%
20m
76%
82%
88%
94%
100% 105%
110%
114% 118%
25m
77%
83%
89%
95%
100% 105%
109%
113% 117%
30m
78%
84%
90%
95%
100% 105%
109%
112% 116%
45m
80%
85%
91%
95%
100% 104%
107%
110% 113%
60m
81%
86%
91%
95% 100% 103%
107%
109% 111%
Figures apply to all DataSafe MX batteries.
The temperature expressed above relates to the monobloc, NOT ambient.
PUTTING INTO SERVICE
If the site acceptance test has been performed, the battery must then be
fully recharged.
LOW VOLTAGE DISCONNECTS
On-load battery voltage should not normally be allowed to fall below
1.7 Volts per cell for discharge times greater than 30 minutes. A low voltage
disconnect must always be used where possible to maintain the integrity of
the battery system. This should completely isolate the battery (including
removing any control circuit load) until power is fully restored to the
charging equipment.
