Key On,
get moving.
Pre-Charging your DC-link is key in high voltage systems - Use our online calculator… save those Pre-charge resistors; or worse contactors welded-shut.
**** These online tools are still under development ****
Some functions may not work or provide accurate results.
Always check and verify calculations by a professional - give us a call
HV Pre-Charge Calculator
Size the pre-charge resistor, estimate charge time, inrush current, resistor energy, residual voltage before main contactor closure, and plot capacitor voltage, current, and resistor power over time.
System Inputs
Calculated Results
Vc(t) + I(t)
Power P(t)
Gathering Inputs
Measure the pack output or HV bus with a properly rated HV meter or isolated measurement device.
Use the actual operating voltage expected during pre-charge, not the fantasy brochure voltage.
Use downstream DC-link capacitance from inverter or load datasheets. Sum every effective capacitance present during pre-charge.
Higher percentage leaves less residual voltage across the main contactor at closure.
Set this from control logic, UX expectations, and contactor sequencing. Faster is not automatically better.
Measure on the assembled system. This estimate is only as good as the resistance value you feed it.
Verify real bus rise, pre-charge duration, resistor temperature rise, and remaining delta-V before main closure.