Hlcbattery manufactures custom lion lithium batteries to meet customer requests. Safety & durable are our priorities.
At present, the main brands in the market are divided into two categories, foreign first-line brands, Sony, Panasonic, Samsung, Sanyo, LG, ranking first and second, basically in a state where money cannot buy goods. Generally, LG and Samsung are the two choices. The domestic ones are basically BAK, Penghui, Lishen, Haisida and so on. These are basically good.
18650 cells can be divided into two categories, one is energy cells, and the other is power cells. This can help you make a choice, capacity type, mainly small current, large air volume, such as 1C, 2C, 3C, 2000, 2500, 3000 mA and so on. Used in lighting, energy storage tools, power type, large working current, 10C, 15C, 20C, 2000, 2200, 2500 mA, etc., mainly used in new energy vehicles, vacuum cleaners, power tools, etc. A single cell is basically between 3.6V and 3.7V.
So how do we choose the right battery for us? Below is a brief description of my own experience. First of all, after getting the sample cells, at least 20 groups, do about ten rounds of charge and discharge experiments, according to the battery specifications, see which battery has more remaining power, and choose the most power. In terms of conditions, as many manufacturers are required to issue relevant certifications, such as UN38.3, MSDS and so on.
Generally, high-quality batteries will have these basic certifications. Finally, look at the selection of the diaphragm of the cell. If the imported diaphragm is selected, it will be a little more expensive than the domestic diaphragm, which mainly affects the consistency of the cell. The battery manufacturer needs to provide relevant certificates.
Safety is essential, drop, acupuncture, high and low-temperature test, etc. If conditions permit, you can do as much as you can, no fire, no smoke, no liquid, and it is a high-quality battery.
The 18650 cells are to be packaged and used. A key issue will be involved here, that is, to choose the PACK factory to make the BMS power management circuit. This is the core part of the 18650 packages. If you choose the right one, it will save a lot of trouble for your products. Relatively speaking, the manufacturers of battery cells generally do BMS management, which will reduce the number of BMS manufacturers and battery cells in the future. The problem of the manufacturer’s wrangling, choose the electric core and let the other party do the PACK for you. In the later stage, the responsibility is clear. If you can do it yourself, you can do it yourself. The packaging process is relatively complicated.
In this case, we focus on the welding process of the PACK board. Flat welding and bump welding can be selected between the battery cell and the nickel sheet. The bump welding is slightly more expensive than flat welding and is safer. Highland barley paper, Whether the insulation protection is in place is the standard for detecting PACK, that is, connecting a single cell in parallel or in series. What is the difference between the two? You can find it online.
Here is an example: The Tesla Model S battery pack is made up of 16 battery packs connected in series, and each battery pack consists of 444 lithium batteries, each 74 formed in parallel. So the Tesla Model S battery pack consists of 7104 18650 lithium cells.
18650 battery balance is a must for the battery pack, it includes active and passive balance. Both have their strength and shortcomings point.
Passive balance appeared before active balance, and it is still widely used today because of its simple circuit and low cost. The principle is that according to the positive correlation between the power and voltage of the battery, according to the voltage data of a single string of batteries, the energy of the high-voltage battery is discharged through the resistance to maintain the same state as the power of the low-voltage battery, and the highest voltage is also used as the criterion, such as ternary. The maximum lithium battery is 4.2V, and if it exceeds 4.2V, it will start to discharge and equalize.
If the equalizing current is large, the heat will be large, and finally how to dissipate heat becomes a problem; if the equalizing current is small, the power balancing effect of large-capacity battery packs with large differences in power is very inefficient, and it takes a lot of effort to achieve balance. For a long time, there is a kind of itching feeling in the application. Weigh the pros and cons, so the current of passive balance is generally at the level of 100mA (100mA).
The benefits of active balance are obvious: high efficiency, energy is transferred, and the loss is only the loss of the transformer coil, which accounts for a small proportion; the balance current can be designed to be large, reaching the level of several amperes or even 10A, and the equalization is effective. Despite these benefits, active balance also brings new problems. The first is the complex structure, especially the transformer scheme. The second is the cost issue. The complex structure will inevitably bring about complex circuits. It is inevitable that the cost and failure rate will increase.
Now the price of BMS with active balance function will be much higher than that of passive one, which also somewhat limits the use of active balance BMS promotion.
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