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Normally precharge will be enabled through a firmware signal from the MCU to the enable pin on the load switch U3. If the firmware is unavailable, this can be powered by connecting a 3v3 3V3 source to the connector P1 and the enable pin (pin 2). This can be done through another power supplyWhenever the enable pin receives power, the isolated side of the board turns on and precharge starts. Before enabling precharge, setup set up the oscilloscope to read voltage output. There are multiple points of interest to be measured over the duration of precharging and discharging. . To precharge and discharge the capacitors, supply and stop supplying the 3V3 to the enable pin on the load switch. With the 3 x 1 kohm resistance for precharge and 1 x 5 kohm resistance for discharge, allow 3s for the capacitor to precharge and 5s for discharge each test. In place of the 150V supplied by the battery, another 12V source can be used to connect to the HV line. The precharge functions should be tested with a lower voltage first.
Test points:
The first point to test is the capacitor itself. Enable precharge and make sure the