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The biggest problem for Tesla is battery cost. They have to increase the production to drive down the price, so they want to leverage SolarCity to sell more Pow

by lukasm 10y ago

The biggest problem for Tesla is battery cost. They have to increase the production to drive down the price, so they want to leverage SolarCity to sell more Powerwalls. Tesla can use solar panels for supercharger stations where grid electricity is not available. You can create a new product or solution etc. etc. There is quite a lot of synergy.

sachingulaya 10y ago
You may be underestimating the power draw of supercharger stations. My model X pulls 200-300Amps of 400V power at a supercharger station with 8-12 stalls. That is over 80,000watts per stall.
- jakub_h 10y ago
  Which is quite an incentive to save on electricity as much as you can, I'd think.
  - hindsightbias 10y ago
    10kW array would be at least 600 sqft, so that will be a lot of commercial real estate. The state/feds should stop subsidizing utility solar and incentivize covered parking lot panels. Prettier than lots and putting the energy where the cars are.
- stevep98 10y ago
  But the stalls work in pairs. They all can't deliver 80kw simultaneously. Ever wondered why sometimes you only get 100A? Because your neighbor, who got their first, gets first dibs on the power, and you get the leftovers.
  - ranman 10y ago
    I've never actually experienced this. I believe the 320 amp / 320 volt charging is for emptier cars... I've plugged in at a 100% full charger and gotten full power charging.
    - stevep98 10y ago
      As you know, the fuller your battery gets, the less current it draws. If your neighbor was already at the end of their charge cycle, then they will be drawing relatively little, and you'll get the full current.
  - sachingulaya 10y ago
    I found this description of a 'typical' supercharger setup: "The eight bay setup takes a 12kV, 750kVA feed from the utility, steps it down to 480V three phase on site, pushes that into 2000A switchgear which feeds four (one for each pair of bays) SuperCharger units at 480V/200A."
- ranman 10y ago
  Just to clarify -- it does not maintain that power. It will quickly ramp up to that on empty-ish batteries (320 amps at 320 volts is max that I know of) and maintain that until the battery is ~50% full. It will then ramp down and charge more slowly. While I can make lots of guesses as to why they charge in this way I don't know for sure on any of them.
  - flyinglizard 10y ago
    This is how Lithium batteries are charged - CC/CV. You first have constant current stage, then as the battery fills up you shift into constant voltage stage where the current is gradually reduced until the battery is full. However CC/CV change doesn't normally happen at 50%, but further down the charging cycle. It may be that Tesla throttles the current ahead of time due to thermal constraints of the charging system.
martinko 10y ago
Eh. Is solar really currently a viable alternative that can power superchargers?
- jakub_h 10y ago
  Technically, it's primarily a DC source. Batteries are a DC sink. It actually seems to make a lot of sense to charge the latter from the former.
  - martinko 10y ago
    Im not really well versed in energy generation - do you have an estimate how many solar panels would be needed to power one supercharger at full capacity?
    - sandworm101 10y ago
      A couple acres? No joke. To generate the 50-80,000watts necessary for each stall you will need city-blocks worth of solar. If it's cloudy or at dawn/dusk, more. If you want to charge cars during the day and night, triple the number of panels and get some massive batteries. Say 120 watts per m2. 80,000/120 =~ 650m2. That's the ideal. Then for dawn/dusk, 1200m2 and triple that to run it at night ... 3600m2 ... just shy of the 4050m2 in an acre. But even that is 3600m2 perpendicular to the sun not on the flat ground. To get that 3600m2 in the real world (not on the equator) you will have to spread the panels out on a much larger lot (much depends on the location and time of year). If I were buying land, I'd estimate 2-2.5 acres for solar per stall.
      - ranman 10y ago
        Just a clarification-- the chargers burst to that 80kW range but they don't maintain it. Typical charging is closer to the 10-20kW range. In addition people are not constantly charging.
        sandworm101 10y ago

by lukasm 10y ago

sachingulaya 10y ago

You may be underestimating the power draw of supercharger stations. My model X pulls 200-300Amps of 400V power at a supercharger station with 8-12 stalls. That is over 80,000watts per stall.

jakub_h 10y ago
Which is quite an incentive to save on electricity as much as you can, I'd think.
- hindsightbias 10y ago
  10kW array would be at least 600 sqft, so that will be a lot of commercial real estate. The state/feds should stop subsidizing utility solar and incentivize covered parking lot panels. Prettier than lots and putting the energy where the cars are.
stevep98 10y ago
But the stalls work in pairs. They all can't deliver 80kw simultaneously. Ever wondered why sometimes you only get 100A? Because your neighbor, who got their first, gets first dibs on the power, and you get the leftovers.
- ranman 10y ago
  I've never actually experienced this. I believe the 320 amp / 320 volt charging is for emptier cars... I've plugged in at a 100% full charger and gotten full power charging.
  - stevep98 10y ago
    As you know, the fuller your battery gets, the less current it draws. If your neighbor was already at the end of their charge cycle, then they will be drawing relatively little, and you'll get the full current.
- sachingulaya 10y ago
  I found this description of a 'typical' supercharger setup: "The eight bay setup takes a 12kV, 750kVA feed from the utility, steps it down to 480V three phase on site, pushes that into 2000A switchgear which feeds four (one for each pair of bays) SuperCharger units at 480V/200A."
ranman 10y ago
Just to clarify -- it does not maintain that power. It will quickly ramp up to that on empty-ish batteries (320 amps at 320 volts is max that I know of) and maintain that until the battery is ~50% full. It will then ramp down and charge more slowly. While I can make lots of guesses as to why they charge in this way I don't know for sure on any of them.
- flyinglizard 10y ago
  This is how Lithium batteries are charged - CC/CV. You first have constant current stage, then as the battery fills up you shift into constant voltage stage where the current is gradually reduced until the battery is full. However CC/CV change doesn't normally happen at 50%, but further down the charging cycle. It may be that Tesla throttles the current ahead of time due to thermal constraints of the charging system.

martinko 10y ago

Eh. Is solar really currently a viable alternative that can power superchargers?

jakub_h 10y ago
Technically, it's primarily a DC source. Batteries are a DC sink. It actually seems to make a lot of sense to charge the latter from the former.
- martinko 10y ago
  Im not really well versed in energy generation - do you have an estimate how many solar panels would be needed to power one supercharger at full capacity?
  - sandworm101 10y ago
    A couple acres? No joke. To generate the 50-80,000watts necessary for each stall you will need city-blocks worth of solar. If it's cloudy or at dawn/dusk, more. If you want to charge cars during the day and night, triple the number of panels and get some massive batteries. Say 120 watts per m2. 80,000/120 =~ 650m2. That's the ideal. Then for dawn/dusk, 1200m2 and triple that to run it at night ... 3600m2 ... just shy of the 4050m2 in an acre. But even that is 3600m2 perpendicular to the sun not on the flat ground. To get that 3600m2 in the real world (not on the equator) you will have to spread the panels out on a much larger lot (much depends on the location and time of year). If I were buying land, I'd estimate 2-2.5 acres for solar per stall.
    - ranman 10y ago
      Just a clarification-- the chargers burst to that 80kW range but they don't maintain it. Typical charging is closer to the 10-20kW range. In addition people are not constantly charging.
      - sandworm101 10y ago