Before you begin, read Micah's page and the related links on how to use our equipment (see: Test Equipment).
Initial board validation:
Before we test the precharge function, check to make sure the board is brought up without problems. This includes checking for short circuits and making parts that should or shouldn't be powered are done so. Using the connectivity function on the DMM, check the pins on the 50POS connector to make sure nothing important is bridged (check with the schematic). Do the same with any ICs. As of this point, basically everything should be unpowered. Look over the schematic and make sure any thing powered from VBAT_PRECHARGE_SW is unpowered. It also doesn't hurt to check isolated side.
Test setup:
Set the voltage/current limit on the power supply to 12V/0.1A and connect it to the VBAT connector P1. This is usually supplied by our power distribution board, and controls whether the entirety of the board is powered or not. Capacitors will be ordered to simulate the capacitors in the motor controllers (see: Future Steps/Considerations). Put the capacitors in parallel by soldering wires to their leads to create ~270uF of capacitance. The capacitors are 4 lead and have the following pin-out:
As seen, the closer lead pairs act as one node on either side of the capacitor. The capacitors should be connected to the P4 connector on the isolated side of the board. P4 is an ultrafit connector, harness wires to a matching connector to connect the board to the capacitors.
Enabling precharge:
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 source to the connector P1 and the enable pin (pin 2). Whenever the enable pin receives power, the isolated side of the board turns on and precharge starts. Before enabling precharge, 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