Ogre
Well-known member
- First Name
- Dennis
- Joined
- Jul 3, 2021
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- 135
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- 7,953
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- Location
- Ogregon
- Vehicles
- Model Y
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- #31
First, I didn’t say average charge speed would be 75 kW. I said half the cars would be charging at 75 kW or less. Thinking on it, that is… probably a bit low. More likely half would be at 100 kW. If you just plug in a destination and follow Tesla’s recommended charging stops, they get you to stops at around 20% and have you leave at a bit below 80% and most stops take 15-20 minutes. At a 250 kW charger, thats when tapering starts and your rate of charge starts going down.I defined my argument as 40x 350kW. Sure that is peak, but it's still pretty impressive? I know they won't all be running flat out, and that is why I said ROI on a poorly utilised setup like that won't be high?
But going from the physical sizes of those two transformers sitting there they are at least 3.5MW to 4MW each. Thats 7 - 8MW total plus megapack capacity. I have a 2.5MW transformer sitting in my backyard connected to our power station and ours isn't as big by far.
On ROI: if 40 stalls are full 10 hours of the day and are charging at 75kW average as you say, and Tesla charges $0.10c premium on every kWh of electricity charged you get $3000 a day or a $1m a year. Not really that great given that it's fairly unlikely to run at that rate.
Do you have any figures on Capex? $5-7m seems about right? $1m for Megapack, $1.75m for the SC units alone, network connection, switchgear transformers another $1m, thats nearly $4m and you still have to do all the roads, stalls, solar, siteworks, planning, approvals, labour and property itself etc. Thats best case 20%, but more likely around 10% ROI. That wouldn't be getting me out of bed in the morning. My last project was 370% over 4 years.
The comment about v4 allowing other brands to charge makes me think utilisation rate is in fact a problem.
After 5 minutes you are at 50% state of charge and your charge rate is down to 150 kW. After 10 minutes you are at 62% SOC and charging at around 100 kW. After 15 minutes you are at 70% SOC and charging at 75 kW.
I think you get the point. Supercharger stations are not designed to operate at peak capacity continuously. V2 chargers would share 150 kW between them. Every V3 chargers are grouped in 4s and have a similar, but more generous maximum draw which is lower than the peak draw rate. (Numbers are approximate)
Charge curves make this all work; the assumption is that someone on the circuit will be at least halfway through their charge cycle.
Since you never have 40 people roll into an empty station at once, it works.
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