Most customers said they want high-quality lithium batteries. How to measure battery pack performance?
Follow with SmartPropel to pay attention to the following 5 tips:
1. Charge-Discharge Rate
The higher the better. “C” is described as the battery charge and discharge current special symbol. 1C discharge represents the current that would have drained the battery from full energy to empty in an hour. Each cell capacity of the BYD E6 Electric Vehicle is 200AH, and the battery 1C discharge current is 200A. When a battery is discharged at a high rate, it usually released less energy than at a low rate.
From the result of tests, the EV battery cell can be seen that the power battery discharge energy of 10C discharge is only 85% of 1C discharge, and 20C discharge energy is only 70% of 1C discharge.
2. Charge and Discharge Cycles
The more the better. 500 cycles is a common value for lithium batteries, which vary from 300 to 3,000 cycles depending on the material. The specific value meaning may vary slightly from factory to factory, and can be roughly interpreted as follows: according to the manufacturer’s regulation of charge and discharge rate (such as 1C discharge, 0.3C charge; from 0% to 100% charge each time, according to this cycle), after 500 cycles, the battery remains at 80% of its original capacity.
The using habits have a great influence on the battery cycle life.SmartPropel gives a few examples to clarify the charge and discharge intensity for the cycle.
If each cycle from 0% charge to 100% , 1C discharge 0.3C charge, 500 cycles later capacity reduced to 80% .This is the most stringent cycle test. Also can be less strict, see below.
If each cycle the power is during 25%-75%, 1C discharge, 0.3C charge, after 2000 cycles, capacity reduced to 80%.
If each cycle the power is during 50%-100%, 1C discharge, 0.3 charge, capacity decays to 80% after 1800 cycles.
From the above examples can be seen that the smaller the charge and discharge rate, the more conducive to life promotion; shallow charge and discharge are also conducive to life promotion.
3. Internal Resistance
The smaller the better. This parameter will be changed due to the different load, temperature and other factors, as the battery life decreases, the internal resistance also increases. The lower the internal resistance, the higher charge and discharge rate. For 18650 cell, normal type internal resistance in about 50 mΩ, power type internal resistance is about 15mΩ.
The lower self-discharge rate the better. For the battery pack, if the self-discharge rate is high when you deliver the finished product to the customer and it has no power, how customers will feel? Plus, it means a lot of energy is wasted. It will also affect the balance of the battery pack, that is to say, the available capacity of the battery pack will be less and less, and the life of the battery pack will be reduced a lot.
For the capacity, internal resistance and charge-discharge curve of the battery produced by the same material and the same process, the higher consistency the better. If 10 cells are series or parallel, and one reaches the over-discharge protection standard, the other cells are still full energy, it will reduce the whole battery pack available energy.
The battery pack lack of uniformity, if there is no protection board is very easy to break, it is easy to overcharge or over-discharge; with the protection board, the available capacity will be lower and lower. The bigger the battery pack, the more consistent it is required.
SmartPropel Original Work Writer：Nancy