E T X T S O L I T H I U M B A T T E R I E S
6
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. 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 graph below illustrate that usable Ah is nearly the same regardless of the discharge
rate (discharge graph lines are nearly on top of each other), with the voltage remaining
above 11.5V for most of the discharge cycle.
Discharge Capacity
