First, let the lithium battery drop to 3.3V through the step-down chip, then supply power to the microcontroller and the Bluetooth module, and plan to raise it to 7V to carry a load.

Result: The bluetooth module does not work and cannot be searched. Remove the bluetooth, the microcontroller and the load are working normally. When the MCU is removed, the bluetooth and the load work normally. Without the use of step-down, when a group of power supplies is separately supplied, all three work normally.

Description: xc6206 for buck and fd6291 for boost.

2. Lithium battery boost and buck problem

Let's analyze the reasons for the above problems, find out the common faults of lithium battery buck-boost, and learn together.

Lithium-ion batteries have a certain range of single voltage. For example, the normal operating voltage range of lithium iron phosphate batteries is 2.5V-3.65V, and the normal operating voltage range of lithium manganate and ternary batteries is 3V-4.2V.

In the application of lithium-ion battery, when the total voltage is 60V and below, a battery protection board is required. Above 60V, a battery management system (BMS) is required. The role of these two devices is to protect the battery from working properly.

Note that after the number of strings of the battery pack is determined, the voltage of the battery pack cannot be adjusted arbitrarily. That is, the voltage change of the battery pack can only change within the normal operating voltage range: when charging, it rises from the lower voltage limit to the upper voltage limit. When using electricity, it will drop from the upper voltage limit to the lower voltage limit.

Understand this problem, if you want the lithium battery to have a wide range of buck-boost, you can adjust it at will.

The best solution: make a set of battery packs, match with a suitable inverter, and then match with a DC voltage regulator, which can meet the step-up and step-down requirements of lithium batteries.

Note: This method is rarely used in practical applications, unless the AC power used is often blackout, or when the battery pack is charged by solar energy or wind, this method of step-up and step-down will be considered.

The boosting and buckling methods of the above lithium battery can be used in the test, and the effect of research and study is good.

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