Forgive me if this has already been discussed... I'm curious as to what most people have their cars set to for the default charge rate at home.
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Typical Home Charge Rate
- Thread starter nwdiver
- Start date
bollar
Disgruntled Member
......... :biggrin:
thecloud
As rhythm raced inside, the ship came alive
Curious about that and whether there is an "optimal" amperage for charging. I primarily charge from a NEMA 14-50 outlet and have been using the default 40A setting to minimize charging time. Recently I've been experimenting with dialing it back as the UMC cable gets quite warm while drawing 40A continuously (something I'm sure everyone else has discovered). Using 32A or less seems to solve that problem. So, assuming there is plenty of time overnight, is 20A going to be more efficient than 30A in terms of minimizing both energy draw and energy loss? The UMC manual says that the outlet must be rated for at least 15A, so that's probably the lower bound, but I always thought that was supposed to be much less efficient than a higher setting.
The lower bound is 5 amps... electrically lower is ALWAYS more efficient; I'm not sure about the chargers themselves... there might be a 'sweet spot' where 20 amps is more efficient than 10. Line losses are Current² x Wire resistance; so the amount of energy lost to heat increases exponentially with higher current. You loose 4x as much energy at 80 amps that you loose at 20 amps.
I've also heard rumors that certain charge levels are better for the battery than others but that's likely temperature dependent and I've never seen anything 'official'.
Lower can also mean you don't run the battery cooling AT ALL... as far as I'm aware battery cooling only runs when its needed. I could be wrong... the pump might circulate coolant continuously but the fans certainly don't run when I charge @ 20 amps unless its REALLY hot outside.
bollar
Disgruntled Member
Would love to see this data on the S! It exists for the Roadster and the results were...
Tesla Roadster Charging Rates and Efficiency - Tom Saxton's Blog
Yeah... I suspect there's a sweet spot... a rectifier and inverter operate in a very similar way and inverter efficiency curves look like this;
That's another reason I picked 20 amps vs 10 or 5... I wonder if Tesla is listening... wouldn't be the first time I got a call from customer service in regards to a post :smile:
Cottonwood
Roadster#433, Model S#S37
I have 80 Amps available, but charge at 56 Amps for half the resistive power everywhere and sqrt(2) the total resistive losses for the charge. Using more than 40 Amps, tests both chargers in the car.
Hmmm... that's a good idea... the car doesn't split it? If I charge @20 amps it's 20/0 not 10/10?
Put in 30, but actually I charge at 33. Even an 33, once in a while the city electricity causes it to go back to 30. This is a problem in this area, not with my house. If I charged at 40 it would jump down to 30 50% of the time rather than once or twice per month.
Cottonwood
Roadster#433, Model S#S37
If you have dual chargers, the car uses one module up to 40 Amps and then splits the load from 41 to 80 Amps.
SW2Fiddler
We Are Cognitive Dissidents
There are probably sweet spots for each type of connection equipment... (Must be a resistance difference between, say, 40A thru a UMC and 40A thru a HPWC)
Leads me to ask, a bit OT, but is there a premium brand of NEMA 14-50 outlet with superior contacts? That connection is a factor we can do something about.
Leads me to ask, a bit OT, but is there a premium brand of NEMA 14-50 outlet with superior contacts? That connection is a factor we can do something about.
For this reason, I charge at 42 amps. That way I'm constantly testing both chargers.
mspohr
Well-Known Member
Edited this to correct my error which was wrong information.
As Cottonwood has pointed out, the power loss is i^2r so it is not linear. You will have lower line loss by charging at a lower current.
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