Analysis and Simulation of Hybrid Battery System on Electric Forklifts

Although lithium-ion battery is becoming more and more popular in energy storage area, lead acid battery still plays an important role in many fields because of its stable and sufficient experience of utilization which makes it be safer. This paper focuses on one of implementation of lead acid battery which is electric forklift. The major function of forklift is to move heavy loads from one place to another place, which means it needs to be started and stopped much more frequently than a daily used vehicle. During braking and cranking process, the current on bus rail of electric forklifts is generally much larger than the rated current of lead acid battery, however, the duration is not long otherwise the battery will be broken. Because of large current, the efficiency of lead acid battery is decreased significantly which is limited by the chemical reaction and the internal resistance. In order to improve the efficiency of lead acid battery during regeneration/boost process, a hybrid battery system is introduced where the super-capacitor is used because of it high power density. In addition, the improvement of efficiency has other advantages like extended cycle life of lead acid battery, smaller volume and mass of battery pack, better economic benefits and so forth.