Charging rate question.

[Mmauer]

If I install 3AWG or 2AWG wire and 1/4" compression lugs with a 50-amp circuit breaker, what should my charging rate be using the Lucid charger?

 

[sdlucid]

Charging current is always limited by the circuit breaker, assuming the wires and chargers are rated for the current. In your case, I guess it's the breaker so (50x0.8) x 240V = 9.6kw
If your panel allows, you may be able to go for a higher amp circuit, if you are using Lucid home charger. For the mobile charger that came with the car, 9.6kw is the limit

 

[lucidtouringman]

If I install 3AWG or 2AWG wire and 1/4" compression lugs with a 50-amp circuit breaker, what should my charging rate be using the Lucid charger?

If your concern is reducing the cross-section area using the compression lugs, then the generic answer would be to introduce as fewer amps through that cross section as are acceptable to you to hit a certain charging rate that works for you if charging overnight. For similar reasons, I keep my charging rate to 30 amps because it doesn't let the battery cooling fans turn on. I could do the math but don't feel like busting on the laptop to pull up my conduit and cable NEC calcs spreadsheet I've been using for 20 years.

 

[Pragmatic]

80% of the 50 amp or 40 amp. The larger wiring is a waste, unless you ever plan to upgrade your panel and add a larger breaker for the charger.