Foreword: In the early days of electric forklift, lead-acid batteries were mostly used, but the lead-acid batteries were large in volume, low in specific energy and easy to pollute the environment. The new type of lithium battery has high specific energy, the same power / capacity, small volume, light weight and long cycle life. Nowadays, the logistics forklift truck generally begins to use lithium battery instead of lead-acid battery. Combined with the industry characteristics and customer needs, our company chooses LiFePO4 battery solution to support customers' electric forklift products. The battery can work continuously with high current. The protection board adopts imported IC and MOS tube for control management, and its service life is 3-5 times that of lead-acid battery.
1. Design requirements for lithium battery of electric forklift:
Battery design is applied to the logistics forklift. It requires small volume and long working time, which can drive two motors: one is driving the car to run, the other is to drive the lifting object. The design of our company's iron lithium battery electric forklift project has a total power of 800W, instantaneous power of 1000W, moisture-proof appearance, long cycle life, high power and high current discharge performance; the whole product is suitable for indoor environment and the temperature rise is low.
2. Lithium battery design scheme of electric forklift:
1) Protection plate (PCM): according to the chemical characteristics of lithium iron phosphate battery and the working characteristics of forklift, the protection circuit is designed for a specific purpose. Besides the functions of overcharge, over discharge, over current and short circuit protection, the design of protection plate also fully considers the problems of high power heat dissipation and battery balance. The whole protection plate adopts aluminum alloy as the heat dissipation base plate, and the temperature rise is less than 20 degrees.
2) Protection circuit: the imported IC and MOS tubes are used to monitor the over charge, over discharge, over current and short circuit functions of the core in real time on line, so that the core can work in a safe, stable and efficient range.
3) Over current fuse: mainly for the lithium battery itself battery management system protection failure design. Because the battery pack adopts high-power batteries with large capacity, although the battery management system has over-current and short circuit protection, if there is any abnormality, the protection function will fail. In the case of short circuit output, very large current will be generated, which will cause danger. Therefore, the over-current fuse is added in the scheme. In case of abnormal short circuit, the fuse will break the circuit and cannot be recovered to achieve the purpose of abnormal protection.
4) Electric core: large26650/3.2v/3000mah iron phosphate lithium battery is adopted. The maximum charging ratio of the core can reach 1C, the maximum discharge ratio can reach 2c, and the core itself has multiple safety protection functions. The thermal resistance (PTC) is built in the core. When combined, the unit structure is also isolated by PTC to prevent the occurrence of surge current.
5) Battery parameters for the whole set: 25.6v/80ah (normally nominal: 24v80ah). The normal working current is 30a, the maximum working current can reach 50a, and the instantaneous starting current can reach 120a.
6) The resistance balance is adopted in the battery pack, which can effectively make up for the capacity reduction caused by the difference of the single cell in the process of use, and maximize the service life of the battery.
7) Parallel cell: PTC isolation is adopted to avoid the inrush safety problem caused by large capacity.
8) The main circuit of high current of the battery adopts copper tape as the current collecting strip, so as to make the discharge current of the single battery close to that of the battery.
9) The battery pack adopts plastic bracket to isolate and fix the electric core, which is more conducive to the cooling and safe use of the battery.