LiPo Balancer calibration
Description of the calibration process for the LiPo balancer
The calibration of the LiPo balancer is very critical because the measured voltage should be very precise in order to minimize the errors in the cut-off threshold calculation. An error in the voltage measurement could traslate the point of start with a potential destructive problem. For the calibration there is the need of a small and stable voltage regulator capable to give with high accuracy the point of start (4.200V) and to give at least the current for the idle state (10-15mA).
LiPo element calibrator building
The LiPo calibrator built is a very simple circuit based on the LM317, one resistor and one trimmer that can give a voltage from 4 to 4.5V. The trimmering range (around the point of start) should be minimezed in order to have a very good and easy adjustement with a standard multiturn trimmer. If the user has a very precise and stable power supply or another adjustable power supply (capable to be trimmered at 4.200V) it can be used to calibrate the LiPo balancer element. We built also a receptacle that accomodate the LiPo balancer element for a better mechanical stability and more reliable operations, but this accessory is recommended but not necessary for the calibration process.
Calibration process description
The calibration is very simple and is divided in two separate steps.
The first step is the calibrator voltage adjust (with an accurate multimeter) in order to have a power supply set EXACTLY to 4.200V. Then the power supply will be removed and the LiPo balancer element is connected to the calibrator. When the power is off the trimmer on the balancer should be turned counter-clockwise in order to prevent an unwanted operation start when the power will be applied. Then apply the power supply, re-check the voltage (stable at 4.200V). The LiPo balancer element will turn on the led at the power on, the turn off it to indicate the "idle" state. At this point the second step is to turn VERY slowly the trimmer on the LiPo balancer element until the start to flash for the LED. At this point stop the turning and the balancer should be calibrated. If the user don't stop turning the trimmer, the overall operation must be repeated, removing the power supply and turning the trimmer in a "idle" position.
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