Some basic common sense memo for power tool power battery pack

From left to right are 5-cell battery packs, 10-cell battery packs, and 15-cell battery packs (electrical tool battery packs will not only affect the life of the tool, but also greatly affect the power of the tool. If you understand, Then don't watch it anymore~)

The water in this line is very deep. Unlike the PC field that I have been familiar with before, many parameters that can be simplified are still not standardized enough, especially in the heart "battery" of commonly used lithium-ion tools.

After researching for a while, big manufacturers generally label batteries AH and V. The former is capacity and the latter is voltage. In addition, there is a key hidden attribute, which is the cell discharge multiple C that some businesses will emphasize. Small factories have a variety of labels, so let's not talk about them.

In general, the core of the power battery pack consists of cells. The battery cell is usually a 18650 lithium battery with a larger appearance than the 5th battery. There are 2 main parameters of the battery cell, capacity, such as 1500 milliamp hours (mah), and discharge rate, commonly 2C~10C. In addition, the standard voltage of this lithium battery is 3.7V, but it can reach 4.2V when fully charged, so the battery pack composed of 5 such cells in series as the basic unit, 18V-21V is actually the same specification , just named differently.

Some basic common sense memo for power tool power battery pack

I synthesized the statements of some battery sellers, and came to the following conclusion, the correctness of the information is not guaranteed, because the junior high school physics has been forgotten...

For large manufacturers, the default batteries are 18650 power type cells, that is, the discharge rate is about 5C (the rate means that the discharge current is the rate of the cell capacity). For example, a cell with a capacity of 2000mah (that is, 2ah) has a voltage of 4.2V and a capacity of 2AH. If it is a 5C rate, then 2AH*5C=10A, which can provide a current of 10A (if it is a 10c cell, that is 2AH*10C=20A) 10A current X3.7V voltage, which is 37W power. If it is a battery pack with 5 cells, then the power X5 is 185W power, a battery pack with 10 cells has a power of 370W, and a battery pack with 15 cells has a power of 555W. If you replace it with 10C cells, the power is twice that of 5C, and the power of a 15-cell battery pack can reach up to 1110W.

If it is a small factory and uses a low-cost battery, then the battery cell is likely to be a non-power battery with a discharge rate lower than 5C. If the capacity is not high, the peak power will be greatly reduced, and the power tool will be "boring". Therefore, the battery pack of electrician tools will not only affect the battery life of the tool, but also greatly affect the power of the tool. The common cheap electric drills on the market are basically based on this principle, and it can be regarded as a reasonable use of "low-end battery products".

Of course, power is the core attribute of the battery pack, but it is not the only important attribute of the battery pack. For example, the internal resistance of the cell. A battery with high internal resistance will generate a lot of heat during high-power discharge. If the heat is large, the anti-overheating protection (if any) will be triggered. If the anti-overheating protection is triggered, then the protection circuit of the battery pack will forcibly reduce the power. can also limit the performance of the tool. Another example is the number of cycles and capacity decay of lithium batteries, the workmanship of protection circuits, etc., which will affect the reliability and durability of the entire battery pack. It's not that the power is high enough and everything will be fine. The so-called quality of the big factory refers to the all-round guarantee of the bottom line. Low-end defective batteries of small factories, the overall power is too low; mid-end cheap batteries, the peak power may be able to see, but due to the internal resistance caused by continuous discharge and heat caused by overheating protection and other reasons, the rated power is not enough; economical batteries, rated The power has come up, but there is still a gap with the first line in terms of the capacity attenuation of the charging and discharging cycle, and the lifespan is low.