User manual

5.1 Introduction
Another area where the CYCLON
®
battery product has a
significant advantage over conventional sealed-lead batteries
is storage. This chapter devotes itself to offering the reader
useful information on properly exploiting the long storage
(shelf) life of CYCLON battery cells and monoblocs.
5.2 State of Charge
The state of charge (SOC) of the CYCLON battery cell can
be approximated by using the curve given in Figure 5-1. This
curve is accurate to within 20% of the true SOC of the cell
under consideration, if it has not been charged or discharged
within the past 24 hours. The curve is accurate to within 5% if
the cell has not seen any activity, charge or discharge, for the
past 5 days.
Figure 5-1: CYCLON
®
Battery Open Circuit Voltage
Vs. State of Charge
5.3 Storage
Most batteries lose their stored energy when allowed to stand
on open circuit due to the fact that the active materials are in
a thermodynamically unstable state. The rate of self-discharge
is dependent both on the chemistry of the system as well as
on the temperature at which the battery is stored.
All CYCLON batteries are capable of long storage without
damage. Figure 5-2 is a plot of maximum storage time as
a function of storage temperature. This curve shows the
maximum number of days at any given temperature, from
10°C (50°F) to 65°C (149°F), for the cell to discharge from
a fully charged state (about 2.14 volts per cell) down to zero
state of charge (1.93 volts per cell). The cell should not be
allowed to discharge below 1.93 volts because of the danger
of damaging the performance characteristics of the cell
permanently.
Figure 5-2: CYCLON
®
Battery Storage Time Vs.
Temperature
It is important to recognise that the self-discharge rate
of CYCLON batteries is non-linear. Thus, the rate of self-
discharge changes as the SOC of the cell changes. In other
words, the time taken for a cell to discharge from a 100%
SOC to 90% SOC is very different from the time it takes to
self-discharge from a 20% SOC to a 10% SOC.
6.1 Introduction
The superior charging characteristics of CYCLON batteries
makes them the power source of choice in demanding
applications that require rapid charging. Conventional
sealed-lead batteries are not suited for this type of charging
where charge currents can be of the order of 2C
10 or higher.
6.2 General
Charging CYCLON sealed-lead acid products, like charging
other rechargeable batteries, is a matter of replacing the
energy depleted during the discharge. Because this process is
not 100% efficient, it is necessary to return more than 100%
of the energy removed during the discharge.
The CYCLON battery cell uses the gas recombination
principle that allows up to 100% of the oxygen generated at
up to the C
10/3 overcharge rate to be recombined to form
water at the negative plate, eliminating oxygen outgassing.
Hydrogen gas generation has been substantially reduced
by the use of pure lead-tin grid material, which has high
hydrogen overvoltage. The corrosion of the positive current
collecting grid has been reduced by the use of pure lead-tin.
The amount of energy necessary for a complete recharge
depends upon how deeply the cell has been discharged, the
method of recharge, the recharge time and the temperature.
Typically, between 105% and 110% of the discharged
ampere-hours must be returned for a full recharge. Thus, for
every ampere-hour discharged, one must put back between
1.05 and 1.10 ampere-hours to ensure a full recharge.
Chapter 5:
CYCLON
®
Battery Storage
Chapter 6:
Charging CYCLON
®
Batteries
1.9
1.93
1.96
1.99
2.02
2.05
2.08
2.11
2.14
2.17
10 20 30 40 50 60 70 80 90 100
State of Charge, %
OCV, V
10
100
1000
3000
10 20 30 40 50 60 70
Storage temperature, °C
Storage time, days
11
Publication No: EN-CYC-AM-007 - December 2008
www.enersys-emea.com