One Golf Cart Battery design solution

发布日期:2023-07-11 21:03
Case (customer demand)

    The lithium iron phosphate battery is used in golf carts, with a nominal voltage of 25.6V and a nominal capacity of 6500mAh. The protection board needs to be equipped with equalization function, communication protocol (bq34z100-g1--I2C), with overcharge, overdischarge, overcurrent, short circuit and high temperature protection, and the plug is a 4P XLR female plug. The battery needs to be placed in a 178*100*60mm black plastic box. The continuous working current of the golf cart is 2-3A, the peak current is 10A, and the peak battery duration is 1S; the working voltage range is 22-29V. The battery cycle life is not less than 1500 times.
Solve the case (case analysis)

1. Difficulties:

①Limited by size, the structural design of the battery pack must be precise;
②The protection board needs to be developed. According to the customer's requirements, bq34z100-g1--I2C is selected to collect battery information. However, limited by the size of the battery, it increases the difficulty of development;
③When I2C communication is connected to the XLR female plug, do not connect the wrong pins. If the connection is wrong, the information collected by the customer's equipment will not match.

2. Key points:

① Optimize the structure of the protection board and battery pack;
② The parameters collected by the customer must be able to be collected;
③The size of the battery box should be accurate, and the outlet hole of the box should match the size of the electronic wire.
Case filing (schematic design)

1. Design idea:

① Select high-quality batteries to meet the requirements of battery cycle life;
②According to the customer's size requirements, the structure of the battery pack is designed to be two layers, the lower layer is 12 batteries placed vertically, and the upper layer is placed four horizontally. Due to the influence of the position of the screw holes in the box, the above four batteries need to stagger this position. Such a design is both beautiful and can meet the size requirements, but it also increases the difficulty of insulation and welding;
③Develop a protective board that meets customer requirements, and can collect battery information, such as voltage, capacity, temperature, remaining capacity, charge and discharge current, and cycle times. Add a mos tube to I²C to protect the IC;
④Adopt 65℃ temperature control switch;
⑤Design the battery box and submit it to the mold factory for production;
⑥Confirm the content and design of the label, the size is consistent with the size of the label on the battery box cover, and submit it to the printing factory for production.

2. Specific plan:

① The program number is: 60008-4;
②Battery core: 26650, 3.2V, 3300mAh. After combination, the cycle life of the battery pack is not less than 1500 times; after standing for 180 days, its charging capacity is not less than 90%. The cycle life is not less than 1000 times;
③ Battery pack structure: 8S2P;
④ Protection board: ④ Protection board: single-cell overcharge protection voltage: 3.77±0.06V; single-cell over-discharge protection voltage: 2.25±0.1V; with bq34z100-g1--I2C communication protocol, with Overcurrent, short circuit and high temperature protection, charging recovery;
⑤ Electronic cable: the cable length is 220mm (including the plug), using 18# cable;
⑥ The shell is black, the size is 178*100*60mm, and it has waterproof function.