1. Lithium battery buck-boost test
First, the lithium battery is stepped down to 3.3V using a step-down chip to power the microcontroller and Bluetooth module. The plan is to boost it to 7V to power a load.
Results: The Bluetooth module did not work and could not be found. Removing Bluetooth allowed the microcontroller and load to function normally. When the microcontroller was removed, both Bluetooth and the load functioned normally. Without using a step-down converter and with a separate power supply, all three components functioned normally.
Note: XC6206 is used for step-down and FD6291 is used for step-up.
2. Lithium-ion battery voltage boost and buck issues
Let's analyze the reasons for the above problems and pinpoint the common faults in lithium battery voltage boosting and deboosting. Let's learn together.
The voltage of a single lithium-ion battery cell has a certain range. For example, the normal operating voltage range of lithium iron phosphate batteries is 2.5V-3.65V, while the normal operating voltage range of lithium manganese oxide and ternary batteries is 3V-4.2V.
In applications where the total voltage of lithium-ion batteries is 60V or below, a battery protection board is required. Above 60V, a battery management system (BMS) is needed. The function of these two devices is to protect the battery and ensure its normal operation.
Note that once the number of batteries in series is determined, the battery voltage cannot be adjusted arbitrarily. That is, the battery voltage can only vary within the normal operating voltage range: during charging, it rises from the lower voltage limit to the upper voltage limit; during power consumption, it drops from the upper voltage limit to the lower voltage limit.
Once this is understood, if you want a lithium battery with a wide voltage ramp-down range, you can adjust it at will.
The best solution is to build a battery pack, pair it with a suitable inverter, and add a DC voltage regulator to meet the voltage boost and buck requirements of lithium batteries.
Note: This method is rarely used in practice unless the AC power supply is frequently interrupted, or the battery pack is charged by solar or wind power.
The above methods for boosting and bucking lithium batteries can be used in experiments and are effective for research and learning.
