E T X S E R I E S L I T H I U M B A T T E R I E S
11
Discharge Curves
Voltage is not a good indication of the state-of-charge in lithium batteries. The first
graph below shows the state-of-charge versus voltage at a 1C discharge rate for the
ETX12 (representative of the ETX series batteries). Typically, lithium batteries require
advanced methods like current counting to track the charge level. As seen from the
graph, the voltage only varies .4V for nearly 80% of the discharge cycle at 25 deg C.
13.4V is a good indication of full charge, while 12.8V is an indication of full discharge at
25 deg C.
The two graphs below illustrates that usable Ah is nearly the same regardless of the
discharge rate, with the voltage remaining above 11.5V for most of the discharge cycle.
8
9
10
11
12
13
14
0
1000
2000
3000
4000
V
mAh
ETX12A/B Discharge Curve (1C Rate)
25 Deg C
8
9
10
11
12
13
14
0
1000
2000
3000
4000
V
mAh
ETX12 Discharge Curve (4Ah, 25DegC)
1C
2C
10C
