Odyssey PC1200 Owner's Manual - page 20
12
Publication No: US-ODY-TM-001 - April 2011
www.odysseybattery.com
fLOAT LIfE
Float life refers to the life expectancy of a battery that is used
primarily as a source of backup or emergency power. Emergency
lighting, security alarm and uninterruptible power systems (UPS)
are good examples of batteries in float applications. In each of
these applications the battery is discharged only if the main utility
power is lost; otherwise the battery remains on continuous trickle
charge (also called float charge).
Since ODYSSEY
®
batteries are dual purpose by design, they
offer a long-life battery option in float applications. At room
temperature (77°F or 25°C) these batteries have a design life of
10+ years in float applications; at end of life an ODYSSEY battery
will still deliver 80% of its rated capacity.
Heat is a killer of valve regulated lead acid (VRLA) absorbed
glass mat (AGM) batteries such as ODYSSEY batteries and
the rule of thumb that relates battery temperature to battery
life is that for every 8°C rise in battery temperature, the float life
is cut in half. This means that an ODYSSEY battery that has a
10-year float life at 25°C (77°F) will have only a 5-year life at 33°C
(91°F) and a 2-1/2 year float life at 41°C (106°F). Therefore if
your float application requires batteries to be in an uncontrolled
temperature environment you should account for battery life that
will be shorter than its design life at 25°C (77°F).
ODySSEy
®
BATTERy STORAGE
AND DEEP DISCHARGE RECOVERy
For any rechargeable battery, storage and recharge are
important criteria. This section provides some guidelines that
will help you get the most from your ODYSSEY battery.
(A) How do I know the state of charge (SOC) of the battery?
Use Figure 2 to determine the SOC of the ODYSSEY battery,
as long as the battery has not been charged or discharged
for six or more hours. The only tool needed is a good quality
digital voltmeter to measure its open circuit voltage (OCV)
1
.
The graph shows that a healthy, fully charged ODYSSEY
battery will have an OCV of 12.84V or higher at 25ºC (77ºF).
figure 2: Open circuit voltage and state of charge
(B) How long can the battery be stored?
The graph below shows the shelf life of the ODYSSEY battery
at different temperatures. At 25°C (77ºF), these batteries can
be stored for up to 2 years. The lower the temperature, the
longer the storage time. Charge the battery before storing it.
The effect of temperature on storage is evident. Roughly,
every 10°C (18°F) increase in temperature cuts the storage
time in half. Thus, at 35°C (95°F) the battery may be stored
for only 1 year before a recharge becomes necessary.
Figure 3 applies only to batteries that are fully charged before
storage.
figure 3: ODySSEy
®
battery storage time at temperatures
(C) Can the battery recover from abusive storage
conditions?
Yes, the ODYSSEY battery can recover from extremely deep
discharges as the following test results demonstrate.
(1) German DIN standard test for overdischarge recovery
In this test, a PC925 was discharged over 20 hours (0.05C
10
rate)
2
to 10.20V. After the discharge
2
a 5
Ω resistor was
placed across the battery terminals and the battery kept in
storage for 28 days.
At the end of the storage period, the battery was charged
at 13.5V for only 48 hours. A second 0.05C
10
discharge
yielded 97% of rated capacity, indicating that a low rate
48-hour charge after such a deep discharge was insufficient;
however, the intent of the test is to determine if the battery
is recoverable from extremely deep discharges using only
a standby float charger. A standard automotive charger at
14.4V would have allowed the battery to recover greater than
97% of its capacity.
These test results prove that ODYSSEY batteries can recover
from abusive storage conditions. Reinforcing this conclusion
is the next test, which is even harsher than the DIN standard
test, because in this test the battery was stored in a
discharged state at a temperature of 50°C (122°F).
State of Charge (SOC), %
Open circuit voltage (OCV),
V
10
20
30
40
50
60
70
80
90
100
13.0
12.8
12.6
12.4
12.2
12.0
11.8
11.6
12.84V or higher indicates 100% SOC
Open circuit storage time in weeks
Percent of 0.05C capacity
10
20
30
40
50
60
70
80
90
100
0
70
30
40
60
50
25C
45C
65C
1
The OCV of a battery is the voltage measured between its positive and negative terminals without the battery connected to an external
circuit (load). It is very important to take OCV reading only when the battery has been off charge for at least 6-8 hours, preferably overnight.
2
The C
10
rate of charge or discharge current in amperes is numerically equal to the rated capacity of a battery in ampere-hours
at the 10-hour rate. Thus, a 26Ah battery at the 10-hour rate, such as the PC925 would have a C
10
rate of 2.6A.