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When daily average is 50-80 miles, the full 40 amp charges in two hours. The mobile connecter and cable gets pretty warm. Does taking the amperage down to say 24amp save component life. Good idea to adjust amps to meet charging time available ?
Lower amps are easier on the electrical service. I generally charge at 32 amps.
the lower the amps, the less heat, the less stress on your components, the less load on the utility, the longer everything lasts.
i backed mine down to 20A and my voltage never goes below ~243v, this tells me i am not stressing the utility or transformer. the car will always recharge to my 60% cut off in the morning (battery is never below 30%)
If I remember my Physics correctly, Joule heating (which is the dissipation of electrical energy via heat when current flows through a conductor) is proportional to the square of the current. Thus, very roughly speaking, charging at 30A will result in approximately half the heat when compared to 40A. And 20A will result in a quarter of the heat when compared to 40A. I charge typically between 20-30A. Like others have said, at 40A everything gets very warm. For my daily commute levels, I just don't see the need to charge at 40A.
You blessed few with 5.0. Rabble rabble rabble.Me? I don't want to have to adjust the car all the time. I leave it at 80A.
Yes, P=(I^2)R. 14 AWG wire is ~2.5 mOhm/ft. The UMC uses 2x 14AWG for each of its conductors, so resistance would be halved with identical parallel conductors; yet since there are two conductors (L1/L2), we multiply x2 again, so total 2.5 mOhm/ft on the cable. 18 ft cable on the UMC, then, should have a total resistance of 45 mOhm. So, the power dissipated across this is (40^2)*0.045, or 72W at 40A. It's 40.5W at 30A, and 18W at 20A.
Now that's just the power dissipated across the UMC cable, nothing else. There's the question of whether cooling pumps have to run and what they draw, the vampire load of having to keep the car awake while charging (charge faster, car goes to sleep faster, for example). We could probably create a huge multi-factor spreadsheet to model it, but why? Elon tells us not to worry. Charge at whatever's comfortable for you.
EDIT: For those wanting HPWC figures, the HPWC uses 1x 6AWG for each conductor. 6 AWG wire is 0.395 mOhm/ft. Multiply 2x for 2 conductors, and 25 ft of cable, so 0.395 * 2 * 25 = 19.75 mOhm. At 80 amps, that's 126W dissipated across the cable. 60A is 71W. 40A is 32W. Note this is for the HPWC, not the UMC.
Me? I don't want to have to adjust the car all the time. I leave it at 80A.
Thanks for the suggestions. I will check this out.If a 40 amp current makes a breaker more than just lukewarm, I'd first suggest checking the torque of the bolts holding the wires to the breaker. Ensure they're tight, a loose connection will generate a lot of heat. If that doesn't cure the heat, you'll want to pull the breaker and check its connection to the buss bar - look for corrosion, pitting, loose clips on the breaker.
Warm @ 80 degrees F with normal inside ambient temps isn't too bad, anything warmer you should worry a bit.
Yes, P=(I^2)R. 14 AWG wire is ~2.5 mOhm/ft. The UMC uses 2x 14AWG for each of its conductors, so resistance would be halved with identical parallel conductors; yet since there are two conductors (L1/L2), we multiply x2 again, so total 2.5 mOhm/ft on the cable. 18 ft cable on the UMC, then, should have a total resistance of 45 mOhm. So, the power dissipated across this is (40^2)*0.045, or 72W at 40A. It's 40.5W at 30A, and 18W at 20A.