||This research attempts to develop a tactical operational strategy for the lithium iron phosphate battery to improve the energy efficiency and flexibility. To improve the energy efficiency and shorten the charging time, the proposed strategy sacrifices a part of the available capacity by making use of the flat-voltage region for general purpose running. On the other hand, the upper and lower limits of the safe operation can be expanded in accordance with the experimental evidences of over-charging/discharging and state-of-health (SOH) tracking. To realize this operation strategy, the battery charging and discharging characteristics are analyzed to induce the more efficient operation region. Accordingly, the voltage differential approach is figured out with constant-current charging. Then, the cut-off points can be determined without the need of the battery parameters from the manufacturer or an accurate estimation of the state-of-charge (SOC), disregarding to differences on battery operating characteristics.|
The feasibility of the proposed strategy has been demonstrated with three different brands of lithium iron phosphate batteries, which are named as A, S, and K, respectively. As compared to the conventionally used constant-current constant-voltage (CC-CV) scheme with a charging/discharging rate of 1 C, Batteries A and S with the differential voltage approach, have a less capacity of 12 % and 10 %, but can shorten the charging time by 16 % and 12 % with improved energy efficiencies of 0.76 % and 0.49 %, respectively, while Battery K has a reduced capacity of about 20 %, but a 31 % shorter charging time with an improved energy efficiency of 0.50 %. Exemplar experiments indicate that Battery A can be over charged by 13 % for a predicative longer duration and has a residual capacity of 9 % for emergent running.