www.odysseybattery.com
11
Publication No: EN-ODY-TM-0002 - February 2015
CYCLE LIFE AND DEPTH OF
DISCHARGE (DOD)
Applications in which the battery is frequently discharged
and recharged are called cyclic. A complete cycle starts
with a charged battery that is discharged and then brought
back to a full charge. Battery life in these applications is
stated as the number of cycles the battery will deliver before
its capacity drops to 80% of its rated value. For example,
suppose a battery is rated at 100 amp-hours (Ah) and has a
published cycle life of 400. This means that the battery can
be cycled 400 times before its delivered capacity drops to
80Ah.
Proper charging and DOD are the two key factors that
determine how many cycles a battery will deliver before it
reaches end of life. The DOD is simply the ratio of capacity
extracted from the battery to its rated capacity expressed as
a percentage. If a 100Ah battery delivers 65Ah and is then
recharged, it is said to have delivered a 65% DOD cycle.
The relationship between DOD and cycle life for ODYSSEY
batteries, excluding PC370, PC950 and PC1100, is shown
in Figure 1. The lower the DOD the higher the number of
cycles the battery will deliver before reaching end of life.
Figure 1
The true dual purpose design of ODYSSEY batteries is
reflected in the cycle life results shown in the graph below.
This graph is from an 80% DOD cycle test completed on
two ODYSSEY 65-PC1750 battery samples. Both samples
gave over 400 cycles before failing to give 80% capacity
(this is classified as end of life.)
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 (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.
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.
Figure 2: Open circuit voltage and state of charge
1000000
100000
10000
1000
Nunmber of cycles
Depth of discharge, DOD% (C
5
)
100
0
10
20
30
40
50
60
70
80
90
100
Charge profile:
[email protected] VPC for 16 hours
Current limit at 1C
0
20
40
60
80
100
120
140
0
50
100 150 200 250 300 350 400 450 500 550 600 650
Run Time in Minutes
Cycle
End of Life -
Sample 1 - Cycle 581
/
Sample 2 - Cycle 544
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
1The 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.
