Tesla Powerwall, The Specs, Numbers, and Implementation Absolutely Brilliant

[tehan]

Cool - thanks for the link. The PowerWall architecture would presumably be different since each PowerWall outputs 350V nominal, so stringing together PowerWalls in series as shown in the SolarEdge StorEdge document you posted doesn't make sense.

I suspect Powerwall and StorEdge have more or less the same architecture. The series connection works very much like the SE optimizers: the voltage is still 350V regardless of how many you connect (i.e. the packs adjust their output voltage based on string length).

[tehan]

Does the product also fake the presence of some number of SE optimizers to satisfy the two way communications need of the SE inverter? Or is there a mode of the SE inverter that does not try to talk to optimizers?

I'm fairly sure it actually contains some number of SE optimizers, or at least a bidirectional version of the SE optimizer. In a battery the SE optimizer is playing the role of charge controller as well as ensuring constant voltage to the inverter irrespective of state of charge or number of packs. It's also providing an important safety feature by preventing the pack from putting out high voltage until the inverter tells it too.

[inetdog]

it is an EU product (don't think it is shipping yet though). it would chain along perfectly fine as the battery optimizers would insure that the bus is putting out a max of 350V that the SolarEdge inverter wants to see regardless of individual battery voltages.

Does the product also fake the presence of some number of SE optimizers to satisfy the two way communications need of the SE inverter? Or is there a mode of the SE inverter that does not try to talk to optimizers?

[ButchDeal]

Cool - thanks for the link. The PowerWall architecture would presumably be different since each PowerWall outputs 350V nominal, so stringing together PowerWalls in series as shown in the SolarEdge StorEdge document you posted doesn't make sense.

Is StorEdge a real product yet?

it is an EU product (don't think it is shipping yet though). it would chain along perfectly fine as the battery optimizers would insure that the bus is putting out a max of 350V that the SolarEdge inverter wants to see regardless of individual battery voltages.

[Cosmacelf]

found this document on SolarEdge's StorEdge solution which seems to be what they are basing their US powerwall solution on.

http://gilleleje-solenergi.dk/downloads/Solar%20Edge/storedge_21_5_14.pdf

It seems to be showing battery optimizers on the second input of the inverter. These optimizers seem to be able to handle different battery sizes and capacities as long as they can chain along up to 350V. It doesn't seem to indicate any grid disconnect device to allow off grid or backup capabilities but that might be done with other equipment.

Cool - thanks for the link. The PowerWall architecture would presumably be different since each PowerWall outputs 350V nominal, so stringing together PowerWalls in series as shown in the SolarEdge StorEdge document you posted doesn't make sense.

Is StorEdge a real product yet?

[Cosmacelf]

Clever like a Fox. Musk goes where ever government money and subsidies go. If not for $35K subsidy he receives for every car sold, he would have been bankrupt years ago. Every business he owns is ran on subsidies if not outright government money like Space-X, buying salvaged Russian Rocket Engines.

SpaceX never bought salvaged Russian rocket engines. Their competitors do. SpaceX engines are their own in house design and built in Los Angeles (Hawthorne).

I would love to see your calcs on $35K subsidy per each Model S sold.

[Sunking]

Some indication where Tesla is going with batteries can be seen in California's Vehicle-Grid Integration (VGI) planning. Consider the Model S uses an AC induction motor. Consider that the Model S has a large inverter that alters both voltage and frequency to power the motors. This design presumably allows the vehicle battery not only take power from the grid, but to put power to the grid.

Not only that, but the car can probably connect to any grid voltage/frequency in the world with no inverter customization. I don't think Tesla gets too much credit. I think they are probably more clever than even their fans imagine.

Clever like a Fox. Musk goes where ever government money and subsidies go. If not for $35K subsidy he receives for every car sold, he would have been bankrupt years ago. Every business he owns is ran on subsidies if not outright government money like Space-X, buying salvaged Russian Rocket Engines.

[donald]

Some indication where Tesla is going with batteries can be seen in California's Vehicle-Grid Integration (VGI) planning. Consider the Model S uses an AC induction motor. Consider that the Model S has a large inverter that alters both voltage and frequency to power the motors. This design presumably allows the vehicle battery not only take power from the grid, but to put power to the grid.

Not only that, but the car can probably connect to any grid voltage/frequency in the world with no inverter customization. I don't think Tesla gets too much credit. I think they are probably more clever than even their fans imagine.

http://www.caiso.com/Documents/Vehicle-GridIntegrationRoadmap.pdf

[Sunking]

Since when did Fortune Magazine become a technology magazine?

[inetdog]

Update on battery chemistry:

http://fortune.com/2015/05/18/tesla-grid-batteries-chemistry/

says

I find the comment on "dirty and expensive" peaker plants poorly informed given that most peaker plants, out here anyway, are gas turbine and relatively clean compared to base load coal plants. They are more expensive though.

[DanKegel]

Update on battery chemistry:

http://fortune.com/2015/05/18/tesla-grid-batteries-chemistry/

says

Tesla CEO Elon Musk said on the company’s earnings call that Tesla will be using a high energy lithium-ion NCA battery for its new grid battery. Similar to the one it uses in its cars, the grid battery is intended for use by utility companies for back-up power. These are the batteries that, when used in a big battery “farm,” could replace so-called peaker power plants, the “dirty” and expensive power plants that utilities use only when grid demand peaks, such as during a sweltering summer afternoon. (The Tesla website describes this as the back-up battery with a capacity of 10 kilowatt-hours and a price of $3,500.)
In contrast, Musk said that Tesla will use a lithium-ion battery with a nickel, manganese, cobalt oxide cathode for its grid battery. Called an NMC battery, it’s meant to be used for daily cycling for a home, business, or certain types of clean power. “There’s quite a lot of manganese in there,” Musk said. (The Tesla website specs for this battery are 7 kWh battery for $3,000.)

[SunEagle]

The little note on the right side of page two is interesting:

• Extends effective battery capacity & lifetime by mitigating battery mismatch & optimizing depth of discharge per battery
• More energy through higher efficiency
• Fault tolerance: If one battery malfunctions the others provide additional power to compensate
• Safety:
• Each battery cell is monitored and the system is shut down in case of a critical battery failure
• Batteries connected in series - low output current
• Battery pack voltage reduced to low voltage in case of system shutdown
• Modular system easily expands in order to accommodate a higher capacity
• Serviceability:
• Easy pack maintenance in case of battery malfunction
• Added/replaced batteries can be of different sizes/types than the original
• Based on SolarEdge’s widely-deployed and field-proven DC-DC power optimizers

It looks like the "battery" may consist of a "maze" of smaller units each one having an individual balance charger. They seem to act as one big battery but may be able to work if one or more have issues.

Pretty complicated for most. Any idea on how long these systems have been in service?

[ButchDeal]

My guess is that the drawing has been simplified just to show off each major "component" of the "system" and not to be used as a wiring diagram.

The little note on the right side of page two is interesting:

• Extends effective battery capacity & lifetime by mitigating battery mismatch & optimizing depth of discharge per battery
• More energy through higher efficiency
• Fault tolerance: If one battery malfunctions the others provide additional power to compensate
• Safety:
• Each battery cell is monitored and the system is shut down in case of a critical battery failure
• Batteries connected in series - low output current
• Battery pack voltage reduced to low voltage in case of system shutdown
• Modular system easily expands in order to accommodate a higher capacity
• Serviceability:
• Easy pack maintenance in case of battery malfunction
• Added/replaced batteries can be of different sizes/types than the original
• Based on SolarEdge’s widely-deployed and field-proven DC-DC power optimizers

[SunEagle]

found this document on SolarEdge's StorEdge solution which seems to be what they are basing their US powerwall solution on.

http://gilleleje-solenergi.dk/downloads/Solar%20Edge/storedge_21_5_14.pdf

It seems to be showing battery optimizers on the second input of the inverter. These optimizers seem to be able to handle different battery sizes and capacities as long as they can chain along up to 350V. It doesn't seem to indicate any grid disconnect device to allow off grid or backup capabilities but that might be done with other equipment.

My guess is that the drawing has been simplified just to show off each major "component" of the "system" and not to be used as a wiring diagram.

I have to admit that showing the use of separate DC "optimizers" for each "battery" would be easier to understand then saying they are Li-Ion balance chargers.

I wonder what the cost of each of those 2.5kWh battery packs are and what their life expectancy is based on DOD% and cycles.

[ButchDeal]

found this document on SolarEdge's StorEdge solution which seems to be what they are basing their US powerwall solution on.

http://gilleleje-solenergi.dk/downloads/Solar%20Edge/storedge_21_5_14.pdf

It seems to be showing battery optimizers on the second input of the inverter. These optimizers seem to be able to handle different battery sizes and capacities as long as they can chain along up to 350V. It doesn't seem to indicate any grid disconnect device to allow off grid or backup capabilities but that might be done with other equipment.