Battery design of electric bicycle

September 15, 2022
Latest company case about Battery design of electric bicycle

With the improvement of people's living standard, "green, energy saving, low carbon, health" will become the standard of all kinds of daily necessities. Electric vehicle is such a product. In recent years, the number of incoming bicycles has increased year by year. The traditional lead-acid batteries for electric vehicles will be replaced by lithium batteries. The battery designed by our company for its electric bicycle is made of 18650 low magnification 3C cell, top pole power management module, 13 strings and 5 parallel. To ensure that the needs of consumers are met.

1、 Battery requirements of electric bicycle:

Because of the large output of the electric bicycle products, the common capacity type electric core can not meet the requirements, only the power core with multiple ratio can be selected. Because of the heavy load, the endurance is far away from the requirements, and the number of power cells required is relatively large. So it is a problem that the battery of E-bike must face and solve to balance. The power management module adopts imported Yipian and specially increases the balance function. The specific parameters of the combined battery are as follows:

1) Model design requirements of lithium battery pack: 18650-13s5p / 48V / 10Ah.

2) Design requirements of circuit part:

1. Single section overcharge protection voltage: 4.25 ± 0.25V

2. Single overcharge recovery voltage: 4.1 ± 0.50v

3. Single section over discharge protection voltage: 3.00 ± 0.08v

4. Single overdischarge recovery voltage: 3.00 ± 0.10v

5. Overcurrent protection value of combined battery (10ms): 45-50a

6. Charge balance current: 300 ± 50mA

7. Charge balance voltage: 4.20 ± 25mV

8. Battery over temperature protection value (recoverable): 70 ± 5 degrees

9. The finished battery also has short circuit and reverse charging protection.

3) Design requirements for battery cycle life: 500 times (GB charging and discharging standard)

4) Design requirements for external dimensions of battery: l
2、 Design scheme of electric tool battery:

1) Protection board (PCM): it is mainly a protection circuit designed for rechargeable lithium battery. Due to the chemical characteristics of lithium battery, it is necessary to provide intelligent power calculation, overcharge, overdischarge, short circuit, overcurrent and other protection functions to avoid combustion, explosion and other hazards.

2) Protection IC: the main protection function chip of the design scheme, which can monitor the overcharge, overdischarge, overcurrent, short circuit and other functions of the electric core on-line at any time. Make the core work in a safe, stable and efficient range.

3) Charge balance module: balance the voltage difference of each cell during the charging process, enhance the consistency of each cell voltage to extend the service life of the combined battery.

4) Temperature switch: mainly designed for temperature protection function. When the temperature of the battery itself reaches 75 ℃ due to other abnormal problems, the temperature switch acts to achieve over temperature protection, and when the temperature drops, it will automatically recover.

5) 18650 lithium ion / 18650 / 2000mAh / 3.7V L (low and high power cell).

6) MOSFET: MOSFET, which plays a switching role in the protection circuit. It will never increase or decrease the voltage at both ends of the load, so as to ensure the voltage stability.