# 12.8 V, 40 Ah, Lithium-Ion (LiFePO4) Battery Aging Model (1000 h Simulation)

This example shows the impact of aging (due to cycling) on a 12.8 V, 40 Ah, Lithium-Ion battery module.

Souleman Njoya M., Louis-A. Dessaint (Ecole de technologie superieure, Montreal)

### Circuit Description

This demo illustrates the effect of aging (due to cycling) on the performance of a 12.8 V, 40 Ah Lithium-Ion battery model. The battery is submitted for 1000 hours, to several discharge-charge cycles at ambient temperature of 25 degrees C , and at various depths of discharge (DOD) and discharge rates. As observed from the Scope, the impact of DOD and discharge rate on the battery life is as expected. As the DOD or discharge rate increases, the battery ages rapidly, which quickly reduces the battery capacity.

### Simulation

The demonstration shows the life cycle performance of a 12.8 V, 40 Ah, Lithium-Ion battery during shallow and deep discharges, at various discharge rates. At first, the battery is cycled to a DOD of 20 % at 0.5 C discharge rate. Afterwards, the DOD and discharge rate are increased to 80 % and 2 C, respectively. Start the Simulation and open the Scope to view all signals.

At t = 0 s, the battery cycling starts with a discharge current of 20 A (0.5 C-rate), at ambient temperature of 25 degrees C. The initial SOC is 100 %. The discharge goes on until the SOC reaches 80 % (DOD of 20%). Afterwards, the battery is charged to 100 % SOC with a charge current of 20 A. As this cycle is repeated, the battery age increases whereas its capacity decreases. The internal cell temperature also increases from 25 degrees C to 33 degrees C.

At t = 200 h, the battery is now discharged to 20 % SOC (DOD of 80 %) and charged to 100 % SOC. This cycle is repeated for another 200 hours. As observed, the battery age starts to increase rapidly.

At t = 400 h, the cycling DOD is brought back to 20 % for another 200 hours. This slows down the aging process of the battery.

At t = 600 h, the discharge current is increased to 80 A (2 C-rate). This causes the internal cell temperature to rise from 33 degrees C to 43 degrees C. As this cycle is repeated, the battery ages more rapidly, which quickly reduces the battery capacity.

At t = 800 h, the discharge current is brought back to 0.5 C-rate for another 200 hours, which slows down the aging process of the battery.

### References

1. O. Tremblay, L.-A. Dessaint, A.-I. Dekkiche, A Generic Battery Model for the Dynamic Simulation of Hybrid Electric Vehicles, 2007 IEEE® Vehicle Power and Propulsion Conference, September 9-13, 2007, Arlington/Texas, USA.

2. N. Omar, M. A. Monem, Y. Firouz, J. Salminen, J. Smekens, O. Hegazy, H. Gaulous, G. Mulder, P Van den Bossche, T. Coosemans, J. Van Mierlo, Lithium iron phosphate based battery - Assessment of the aging parameters and development of cycle life model, Applied Energy, Volume 113, January 2014, Pages 1575-1585.