Electric Vehicle Charging

[Radix2]

Looking to finish up the electrical service before closing up the garage walls.

We have had a EV in the past (Volt) with a level 2 240v EVSE this had a dedicated 30A feed and a separate EV meter.

On my new garage I want to make provisions for a full on EV as best we can foresee what the requirements will be.

The heaviest draw I see for current vehicles is for a Tesla with the High Amp charging option - 72A

There are a couple of special considerations for derating that I want to review here to make sure that they are right.

The garage is attached to the house, so the cable will be running from the 400A main service to a spot on the garage wall inside a insulated wall- so wiring buried in insulation.

EV charging is considered a continuous load - so wiring and breaker needs to be upsized by 125% - 72A ->90A

Wire used will be SER and in insulation so 60C Ampacity , 72A continous ->1/0 AL, EVSE requires 3 condictors +ECG - > 1/0 1/0 1/0 2 cable. Distance is 30 feet, 90A breaker.

This would be the design required to support the current Telsa EV w/fast charger.


I am thinking that since the cable is so unwieldy and that I would like the ability to use it for welding in the garage - it makes sense to run from the main to a subpanel at the garage wall and leave it at that for future connection to a EVSE and a 50A welder plug now.

So this changes the wiring to 72A continuous and 50A noncontinuous -> 4/0 and a 150A breaker. (might be 3/0 125A ? min for a assembly rated for continuous load).

The good thing I suppose is that if I want capability beyond the Telsa, I could remove the welding circuit and have a 120A continuous feed available.

So my plan is 4/0 4/0 4/0 2/0 150A feed to to a subpanel with just a 50A circuit now.

I used the sizing calculator at http://www.electriciancalculators.com/calculators/wireocpd_ver_1.html for the wiring.

I want to make sure I have the right deratings in there for the insulation as well.

 

[matt_i]

I don't think the 4/0 is going to land on a 50A double pole breaker terminals if I am understanding correctly. (terminal not sized for massive diameter wire). If it were me I'd build the subpanel to the full ampacity you intend, then wait to build the field-wiring from there until you know what kind of needs you have.

Also 4/0 neutral nor 2/0 ground will land on typical drilled bar without special lugs there as well.

 

[Radix2]

I don't think the 4/0 is going to land on a 50A double pole breaker terminals if I am understanding correctly. (terminal not sized for massive diameter wire). If it were me I'd build the subpanel to the full ampacity you intend, then wait to build the field-wiring from there until you know what kind of needs you have.

Also 4/0 neutral nor 2/0 ground will land on typical drilled bar without special lugs there as well.

yep the 4/0 is to the subpanel will be waiting for the EVSE as req'd.

 

[rwilner]

I just ran 10/3 to each bay for exactly what you describe. The 10/3 copper across the 36' garage was unwieldy enough for me!
I figure 30a @ 240 will be way better than 20a @ 120, and since the normal use case at home will be to plug in for the night, it should do fine. Also - I figure as tech improves, amperage requirements should decrease.

The 240v 30a outlets also do me for welding.

I know I didn't answer your question but wanted to share my thoughts.

Sent from my Nexus 7 using Tapatalk

 

[manwithtools]

Also - I figure as tech improves, amperage requirements should decrease.
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The opposite is true. As technology improves, the batteries will require more current to recharge as they will be holding more energy - this is really the only way the e-cars succeed, they need to store more power to give greater range. This is actually part of the problem with the electric car model. More and better electric cars will require more power from an electric grid that can't support it.

Can you imagine 35% - 50% of the cars in a downtown parking garage needing a 60 Amp drop to quickly charge them? There would need to be a substation next to the parking garage... and more power plants to supply the energy.

Or 35% - 50% of the cars in a cul-de-sac needing a 60 Amp drop to quickly charge them so the soccer moms can deliver the kids to their destinations every day after school? There would need to be a substation next to the sub division ... and more power plants to supply the energy.

Don't count on renewables to provide that extra power either, the soccer moms need their power after the sun goes down and the wind dies down (this time of year at least).

BTW, I've owned an electric car and installed 15 - 18 MW solar generation facilities. I'm not a pessimist, but rather a realist when it comes to this technology.

 

[Radix2]

Thanks for your thoughts guys.

Well, looks like the Siemens 200A panels don't have a 150 breaker, 125 is the max.

 

[rwilner]

Just as a counterpoint, I have a buddy in CA that has two fully electric vehicles and he is 100% off the grid with a combination of solar, wind, and battery storage, as well as an inertial generator.

This is obviously the extreme and no one can predict the future...but I believe battery energy density is going to increase by at least one order of magnitude in the next 5 years.

Your statements are true, but assume greater market penetration at existing tech levels...I'm bullish that the tech will get better in parallel with market penetration.

Tesla just came out with those solar roof shingles. Those look sweet.

Anyway - my point was that the main value of big amperage is charging speed. At home - when most people would (and do) charge their cars - the use case is more like your cell phone, plug it in at night. I think 8 hours is a doable duration at 12/120 to fully charge most any ev.

You're certainly right that the use case in a parking garage or public place would require more speed.

Anyway, OP, sorry to hijack your thread. I have a copy of the 2014 NEC if you want me to look something up

Sent from my Nexus 7 using Tapatalk

 

[wyliesdiesels]

Looking to finish up the electrical service before closing up the garage walls.

We have had a EV in the past (Volt) with a level 2 240v EVSE this had a dedicated 30A feed and a separate EV meter.

On my new garage I want to make provisions for a full on EV as best we can foresee what the requirements will be.

The heaviest draw I see for current vehicles is for a Tesla with the High Amp charging option - 72A

There are a couple of special considerations for derating that I want to review here to make sure that they are right.

The garage is attached to the house, so the cable will be running from the 400A main service to a spot on the garage wall inside a insulated wall- so wiring buried in insulation.

EV charging is considered a continuous load - so wiring and breaker needs to be upsized by 125% - 72A ->90A

Wire used will be SER and in insulation so 60C Ampacity , 72A continous ->1/0 AL, EVSE requires 3 condictors +ECG - > 1/0 1/0 1/0 2 cable. Distance is 30 feet, 90A breaker.

This would be the design required to support the current Telsa EV w/fast charger.


I am thinking that since the cable is so unwieldy and that I would like the ability to use it for welding in the garage - it makes sense to run from the main to a subpanel at the garage wall and leave it at that for future connection to a EVSE and a 50A welder plug now.

So this changes the wiring to 72A continuous and 50A noncontinuous -> 4/0 and a 150A breaker. (might be 3/0 125A ? min for a assembly rated for continuous load).

The good thing I suppose is that if I want capability beyond the Telsa, I could remove the welding circuit and have a 120A continuous feed available.

So my plan is 4/0 4/0 4/0 2/0 150A feed to to a subpanel with just a 50A circuit now.

I used the sizing calculator at http://www.electriciancalculators.com/calculators/wireocpd_ver_1.html for the wiring.

I want to make sure I have the right deratings in there for the insulation as well.

How much of the wire will be in insulation?

 

[Radix2]

How much of the wire will be in insulation?

I'd say just about all of it - if it is run inside the walls.

 

[wyliesdiesels]

I'd say just about all of it - if it is run inside the walls.

Then you are correct about needing to use the 60* c ampacity for SER