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The third article of the energy storage series; the whole series is estimated to have 20~30 articles;
In the previous article, I made a preliminary understanding of the application and function of lithium batteries for two-wheeled electric vehicles;
Today we look at the calculation of lithium battery series and parallel connection and capacity;
And the actual application of electric vehicle lithium battery and lithium battery charging & protection board (BMC);
The following figure is a wiring diagram of the same port, both ends of the cell are connected to the row sub-interface of the BMC; (the further device-level disassembly of the BMC will be introduced in the next chapter)
The actual wiring picture is as follows, the cells are connected together through series and parallel;
Here, you may have questions, how to connect batteries in series, and what is the specific voltage?
First briefly explain the series and parallel, which belong to the basis of the circuit;
Connecting in series increases voltage, paralleling increases current. The standard voltage of ternary lithium is 3.7v, full of 4.2v, we calculate according to the standard voltage, three strings is 11.1v, 48v requires 13 batteries in series;
The standard voltage of iron-lithium charging is 3.2V, about 3.7v when fully charged, and 15 strings are required for 48v;
Connect 2 cells of the same model and capacity in parallel, the voltage remains unchanged, and the current is multiplied by 2, so the capacity is also multiplied by 2;
For different models, there will be batteries with different voltage levels (number of cells in series) and different current levels (number of cells in parallel), as shown in the figure above
Well, let’s calculate the following performance parameters. If you understand the calculation, you will understand.
Here, there is another question, why are the charging current, standard discharge current, and maximum discharge current of the charger different? From the perspective of standards and units, you can check the C index of the battery cell;
The next article will introduce the device-level dismantling of the battery management board BMC, and briefly talk about the battery analog front-end AFE, MCU, op amp and other chips inside;
Welcome to pay attention to the official account and go deep into the chip industry chain together;
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