Quote:
Originally Posted by ThunderPorpoise
We've thought about capacitors, but we're not sure they're legal.
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No, they're not FRC legal in that application.
Yes, in theory you could put a capacitor across the motor controller's power inputs.
But let's do a very rough back-of-the-envelope calculation.
Let's say you wanted the capacitor to provide 40 amps for 1/4 second to mitigate the current surge. That's 10 Coulombs of charge.
Let's say the capacitor started at 12 volts (fully charged) and you want the capacitor's voltage to be no lower than 11 volts after discharging that 10 Coulombs.
What's capacitance would be required?
C = dQ/dV = 10/1 = 10 Farads.
Let's put 10 Farads into perspective.
See that big blue capacitor at the top of
this image? It's 45,000 microFarads. It's 5.7 inches long and 1.7 inches diameter.
It would require 220 of those wired together in parallel to give you 10 Farads.
Or, for only $250, you could wire 10 of
these in parallel to get a 10Farad 20V capacitor.