Downgrading the Charge Station Pro amperage

[Tomwilli2025]

Existing unused breaker sizes mean nothing. You electrician should be able to do an NEC load calculation and determine your remaining capacity. I’d bet you can utilize the full capacity of the FCSP.

Understood. I plan on having my electrician do a load calculation. I'm just working on a parts list for budgeting at this point. Electrical components have really increased in cost so higher amperage circuits increase the cost substantially. I was thinking that a 70-amp circuit may be most practical in my case because of wire size for 60-amp is the same 70-amp but I cant find a 70-amp disconnect so I would need to buy a 100-amp sub-panel and put a 70-amp breaker in it. If my run for the main panel to the garage wasn't 115ft it would be so bad. 2 AWG wire for a 100-amp circuit is pretty spendy.

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[Maquis]

Understood. I plan on having my electrician do a load calculation. I'm just working on a parts list for budgeting at this point. Electrical components have really increased in cost so higher amperage circuits increase the cost substantially. I was thinking that a 70-amp circuit may be most practical in my case because of wire size for 60-amp is the same 70-amp but I cant find a 70-amp disconnect so I would need to buy a 100-amp sub-panel and put a 70-amp breaker in it. If my run for the main panel to the garage wasn't 115ft it would be so bad. 2 AWG wire for a 100-amp circuit is pretty spendy.

Your electrician will probably recommend aluminum wire for this. It’s much less expensive and in spite of many still believe, is just as safe as copper, especially in these larger sizes. In my area, #2 copper is $1.92 while #1 aluminum is $1.19.

 

[Tony Burgh]

Aluminum, properly installed, is safe. Mix and match and you’ll be buying trouble.

 

[Tomwilli2025]

Your electrician will probably recommend aluminum wire for this. It’s much less expensive and in spite of many still believe, is just as safe as copper, especially in these larger sizes. In my area, #2 copper is $1.92 while #1 aluminum is $1.19.

Thanks for the recommendation. I will discuss with my electrician.

 

[Maquis]

Aluminum, properly installed, is safe. Mix and match and you’ll be buying trouble.

If listed connectors are used, it’s not a problem. A transition from copper to aluminum is common when connecting to devices that only allow copper.

 

[jefro]

How many miles do you think you will drive each day?

 

[Tomwilli2025]

I don't drive more then 75 miles a day but I get called out on road trips with a days notice. Weekends are different, trip to farm and lake which are both 200 miles round trip. I'm sure a 60-amp circuit would be fine most of the time but since I have to pull that circuit I'm thinking why not go large. I realize going big cost money.

 

[Tony Burgh]

If listed connectors are used, it’s not a problem. A transition from copper to aluminum is common when connecting to devices that only allow copper.

Correct. Use the connectors designed to transition from onto the other with non corrosive dielectric.

 

[Labs4Lightning]

Your electrician will probably recommend aluminum wire for this. It’s much less expensive and in spite of many still believe, is just as safe as copper, especially in these larger sizes. In my area, #2 copper is $1.92 while #1 aluminum is $1.19.

I went with aluminum - in my case it saved me over $300(just wire material) because my run is long.

 

[jefro]

Hope this gets updated to show you how long it will take to charge at various levels. https://evcompare.io/charging-calculator/
I assume you can use e-tron since it is almost exactly the same.

75 miles might be 24Kwh to maybe 50 in harsh conditions.

At 24 it's simple to recover under 24A in a few hours.

200 mile trips will have to plan on DC or destination charging.

 

[chl]

Aluminum, properly installed, is safe. Mix and match and you’ll be buying trouble.

Might be easier and might be cheaper to just use copper throughout than to use Al then add copper ends (Copalum connectors) unless you already have Al wire installed or have an exceptionally long run.

Most EVSE's aren't designed for Al wire - their wire terminals are designed for a certain size of copper wire based on the current capacity/rating - Al wire carrying the same level of current has to be larger diameter.

Al wire has to be handled more carefully - it breaks when bent more easily than copper, and must be terminated properly to avoid oxidation and the resulting overheating that can cause.

Many of the failures of EV charging equipment in recent years, such as the ones in popular videos from Sandy Munro or Tom M, involve aluminum wire, mostly likely failing because it was not terminated properly. (These videos don't provide good information on working with aluminum, but are just high-profile examples of the problems.)

See: https://www.reddit.com/r/evcharging/wiki/aluminum/
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Some reasons why using Al wire for general household wiring is a fire risk:
Al oxidation problems = cause resistance to current flow = heat = melted insulation = fire risk;
Coefficient of thermal expansion is higher than copper which will causes Al wire to loosen at terminals on switches, outlets, etc. over time leading to increased resistance;
Al wire breaks more easily when bent or stapled during installation.

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