How many go full send when charging at home?

[bigsky]

Running a continuous load at 80% of breaker capacity is the maximum.
Best to stay well below that for longevity and efficiency.

Running a continuous load at 80% of breaker capacity is the maximum.
Best to stay well below that for longevity and efficiency.

I don't think that derating a wall charger down to evn 0.01 A will make one bit of difference at all in the grand scheme of things because the wall charger may not necessarily be the weakest link, or the item with lowest MTBF in the entire AC in- wall charger- EV AC-DC converter-battery pack
Indeed, I have heard of battey packs on Teslas rated for, say 2,000 cycles. In other words, my Tesla battery pack may very well give out first, die, but by damn, I derated the hell out of the wall charger, and it still works, even though EV is dead. Woohoo!!
And a battery pack cannot be derated, I don't think. The working voltage, that is.

Therefore, when looking at this wall charger derating from a practical point,one begins to see that the argument for derating it becomes rather an academic exercise and argument, a rather silly proposition,in other words. It serves no useful purpose in terms pf longevity and quicky becomes a just-because exercise with no value-add whatsoever.

And, AND, how do you know that a Tesla wall charger at 48 A, or any other wall charger for that matter operating at maximum charging rate is not derated alread!?

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[docwhiz]

Yes, the wall charger is not usually a problem. It's the wires, plugs, connections, in car charger, battery that a more likely to be stress by large current flows.

 

[Shmoe]

Retired but I typically burn off 20-40 miles a day. I have a Level 2 EVSE outside on it’s own 60 amp circuit, but most days I just pull into the garage and connect to the Level 1 charger as I exit the truck. Typically by the time I take the R1 back out the next day it is back to 70%. If I need to charge more quickly or have a longer road trip coming up, I use the Level 2… usually to 70%… once a month or so to 95-100 before a 300 mile round trip.

There is still an inherent inefficiency in 110V charging which means you are burning a good amount of kWhs in the aggregate for no great reason.

 

[Bubbsgrampa]

I run the full 48A on a 60A circuit. It’s a dedicated hard wired connection and the conduit runs along the wall so almost nothing is hidden. I don’t worry about anything melting.

Exactly the same here.

 

[ndmiller]

Chargepoint on 14-50 outlet charging at highest rate for both EV's. Don't understand why I would change it and not sure I know where to look to do so.

 

[PhatDaddy]

There is still an inherent inefficiency in 110V charging which means you are burning a good amount of kWhs in the aggregate for no great reason.

I was not aware of that…can you suggest sources explaining? Thanks.

 

[radiator]

I was not aware of that…can you suggest sources explaining? Thanks.

The biggest is that the truck must be awake to charge. The idle computer use has been quoted to be 600-900 w an hour.

so if you are charging at 120v in a 15 amp circuit, you are putting in at most 1800 w per hour, but fighting a truck charging overhead of 600-900 w, so only 900-1200 goes into the truck. The longer charge duration means you spend more hours with the computers running doing nothing.

By contrast, if you charge at 120v 20 amp or even 240v 20 amp, you are getting more charge into the truck faster meaning the computers run for less total time, yielding less wasted idle energy usage.

 

[PhatDaddy]

The biggest is that the truck must be awake to charge. The idle computer use has been quoted to be 600-900 w an hour.

so if you are charging at 120v in a 15 amp circuit, you are putting in at most 1800 w per hour, but fighting a truck charging overhead of 600-900 w, so only 900-1200 goes into the truck. The longer charge duration means you spend more hours with the computers running doing nothing.

By contrast, if you charge at 120v 20 amp or even 240v 20 amp, you are getting more charge into the truck faster meaning the computers run for less total time, yielding less wasted idle energy usage.

Makes sense. Thanks for the info!

 

[Shmoe]

Makes sense. Thanks for the info!

Also to what I was getting at 120V is ~80% efficient (20% burned off in heat/inefficiencies) whereas the 240V is typically around 90-97% efficient.

It's not much in the micro, but it certainly adds up in the macro.

 

[stormbreaker]

I have 12kW of solar outputting 9kW. I charge when the sun is high and my charger pull 8.8kW, leaving 200w to keep the fridge cool.

So yea, full send.

I try to do this very thing with my 8.8kw array. However I still pull street power since the Rivian wall charger outputs 10.5kw to the battery. So I only charge at home during the summer when its really sunny out. Otherwise, work is .20 per kwh.

 

[zefram47]

I only have a 30A outlet for now, so I charge at 24A. It allows me to do around 55 kWh overnight when my normal usage is around 25 kWh/day, so it works. If I need more than that overnight, I either eat the higher ToU rate or go to a DCFC and top up just enough that I can do the rest at home. When my wife finally gets an EV I'll likely upgrade to a 60A outlet and either get a power-split/dual EVSE or just charge every other day at 48A.

 

[NeedSumCoffee]

As far a I know Teslas can level 2 up to 48 A only same for Rivians. Unless charging two of them at once, what do you gain using such a charger if with one Tesla or Rivian?

My 2017 Model X has dual onboard chargers and can charge up to 80A. The older Gen2 wall chargers support the 80A charge rate.

 

[bigsky]

My 2017 Model X has dual onboard chargers and can charge up to 80A. The older Gen2 wall chargers support the 80A charge rate.

What!?
Wow.

 

[carsly]

My 2017 Model X has dual onboard chargers and can charge up to 80A. The older Gen2 wall chargers support the 80A charge rate.

19kw? That's faster than most (working) EA chargers!

 

[kostyaaf]

Charging at lower current not only means that more of the vehicle is awake but also the onboard AC/DC converter is operating in lower efficiency range.
On the truck I only noted data for EVSE reported vs total energy truck reported (no HVAC, etc). I see ~ 94% conversion efficiency at 48A and 92.7% at 30A.
I did find this for Mach E and it matches what I'd expect: https://www.macheforum.com/site/threads/onboard-charger-efficiency-measured.32983/

Personally - the only reason I reduce is if I know that the connected power system will overload (ex. when using adapters to dryer plugs).

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