Foreword: the electric forklift truck tends to apply lead-acid battery at the beginning, but lead-acid battery has shortcomings of large size, low specific energy and is bad for the environment. New lithium ion battery has high specific energy, small capacity and size under equivalent power, light weight and long cycle life. Nowadays, logistics forklift truck begins to replace the lead-acid battery with lithium ion battery. Integrated industrial characteristics and customers’ requirements, Large Electronics decides to choose lithium iron phosphate battery scheme assorted with electric forklift truck products. Lithium iron phosphate battery can work under large current and its guard plate adopts imported IC and MOS for control management, which has 3-5 times longer cycle life than lead-acid battery.
I. Lithium ion battery design requirements of electric forklift truck:
The battery is designed for logistics forklift truck and is required for small size, long working hour and can drive two electrical machines: one for car driving, the other for lifting objects. Large Electronics lithium iron phosphate battery design scheme has total power of 800W, instant power of 1000W, damp-proof appearance, long cycle life, good discharging performance under high power and large current. The whole product is adaptable for indoor environment and has low temperature rise.
II. Lithium ion battery design scheme of electric forklift truck:
1）PCM: based on the chemical characteristics of lithium iron phosphate battery and operating characteristic of forklift truck, the scheme contains specific protection circuit, which not only has functions of overcharging, over-discharging, overcurrent, short circuit, etc., but also adopts aluminum alloy as radiating substrate for the whole PCM and its temperature rise is less than 20℃ due to heat dissipation under large power and balance issue of the battery pack.
2）Protection circuit: it adopts imported IC and MOS, and has on line monitoring for battery functions of overcharging, over-discharging, overcurrent, short circuit, etc., which helps battery works under safe, stable and efficient circumstance.
3）Overcurrent fuse: It is designed for protection failure of lithium ion battery management system. The battery pack applies large power cell with large capacity. Although battery management system has protection of overcurrent and short circuit, it still leads in protection failure when abnormal circumstance occurs. Large current is produced under output short circuit and results in danger, so there is overcurrent fuse in the scheme, so that the fuse will cut off the circuit irretrievably for abnormity protection when short circuit occurs.
4）Battery: Adopt lithium iron phosphate battery of LARGE26650/3.2V/3000mAh. The maximum charging rate of this battery is 1C, and maximum discharging rate is 2C. The battery has multiple protective functions. It has thermistor (PTC) inside the battery and separates single battery by PTC, which prevents inrush current phenomenon.
5）The parameters of the whole battery pack: 25.6V/80Ah (nominal parameter: 24V80Ah). Its maximum operating current can reach 50A, and constant starting current is 120A.
6）The battery pack use resistance equalization inside, which can effectively deal with the capacity reduction due to the differences between single batteries and expand the cycle life as much as possible.
7）Battery connected in parallel: Be separated by PTC so as to avoid inrush current issues led by large current.
8）The large current main circuit of the battery adopts copper strips for collector and prevents the discharging current of single battery to be closed to each other.
9）The battery pack adopts plastic holder to isolate and fix the battery, which does good to heat dissipation and safety application of the battery.