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

[Cosmacelf]

I know there is a lot of skepticism here about Tesla and their, currently, specware battery. But I think it is misplaced. Tesla is truly the world leader in making high performance, low cost, low degradation large lithium ion batteries. Just as the other car manufactures haven't been able to match Tesla's battery cost, I suspect Tesla will also be a leader in home storage batteries too. While there will be some cost advantage for FLA, I think it'll be offset by the ease of install, compact footprint, and lack of maintenace for the lithium ion batteries. The only warranted skepticism is when will it ship since Tesla isn't known for keeping to promised schedules.

[donald]

Seems like the first version is so unusable for most people that they needed to make changes very quickly. I wonder how much Beta testing went into the new version.

Tesla uses half the worlds lithium battery production. Tesla cars have driven a billion miles. Tesla has half the market cap. of Ford, and 11,000 employees.
Yeah, they are just throwing product out into the market without much thought.

[donald]

The rumor I heard is that they changed the internal series/parallel cell wiring to allow for higher discharge rates at the battery level.

I doubt it. The cell count, cell voltage, and pack voltage is a constant in the powerwall.

If you look at how the individuals cells are wired in the car battery there is nothing to change to improve the C rate. Choosing the C rate is about battery longevity, not wiring.

[donald]

I think Tesla initially picked a low C rate because they had not decided on the final spec. They then created some buzz by improving the spec. Plus it leaves all the company's that announced home battery products in their wake somewhat wrong footed.

[Cosmacelf]

The rumor I heard is that they changed the internal series/parallel cell wiring to allow for higher discharge rates at the battery level. They realized that it would be more useful to have more power for a shorter period of time than to string out the power for longer. Presumably this changes other spec items as well. Since the batteries have yet to ship, and are still 3 months away from shipping, at best case, they could make this change without too much trouble. They made the change in response to partner criticism about the initial specs.

The 5kw/7kw power output changes are supposed to be for both the 7kwh daily cycler battery and the 10 kWh backup battery. They also said the 7kwh battery has a lifetime 5,000 cycles, whereas the 10kwh battery can do 1,200 cycles. They didn't specify what degradation percentage you are left with at the end of these cycles.

[SunEagle]

I assume the inverter controls the discharge rate. So they have probably only changed the spec. the inverter software programmer can use.

Maybe. By going with a higher discharge rate (from 2kw to 5kw) those batteries must be able to handle a fasted C/x rate then before. That could be just a program change that allows a faster discharge rate or maybe the battery chemistry has been tweaked.

[donald]

First off which system (7kw or 10kw) are you referring to?

Second, did Tesla change the software or hardware to increase the 2kw to 5kw output with a 7kw peak output?

Seems like the first version is so unusable for most people that they needed to make changes very quickly. I wonder how much Beta testing went into the new version.

I assume the inverter controls the discharge rate. So they have probably only changed the spec. the inverter software programmer can use.

[SunEagle]

Yeah, 5kW continuous, 7 kW peak. He also said something else interesting at the Tesla shareholder's meeting. Normally with a backup generator, it only powers a critical load panel. Musk indicated that with one or more of these Powerwalls, you could flip this around and power the whole house, minus the high energy, non-critical loads like air conditioners in a backup scenario.

First off which system (7kw or 10kw) are you referring to?

Second, did Tesla change the software or hardware to increase the 2kw to 5kw output with a 7kw peak output?

Seems like the first version is so unusable for most people that they needed to make changes very quickly. I wonder how much Beta testing went into the new version.

[Sunking]

Yeah, 5kW continuous, 7 kW peak. .

So now he changes his story line. You know what that means right?

[Cosmacelf]

Yeah, 5kW continuous, 7 kW peak. He also said something else interesting at the Tesla shareholder's meeting. Normally with a backup generator, it only powers a critical load panel. Musk indicated that with one or more of these Powerwalls, you could flip this around and power the whole house, minus the high energy, non-critical loads like air conditioners in a backup scenario.

[Sunking]

The beginning of the end for FLA.

Wake up it is just a dream.

[SunEagle]

Tesla updated the powerwall spec to 5kw output. Musk also said they would preferentially supply installers who sold at his low price. He said the powerwall should be installed for about $500 added to the price. Obviously this price assumes a compatible inverter.

The beginning of the end for FLA.

Time to dump the Pb stocks and get some Li instead.

[donald]

Tesla updated the powerwall spec to 5kw output. Musk also said they would preferentially supply installers who sold at his low price. He said the powerwall should be installed for about $500 added to the price. Obviously this price assumes a compatible inverter.

The beginning of the end for FLA.

[Sunking]

But isn't that just how tech happens? Take car engines. Thirty years ago you could work on your own engine, change the spark plugs, replace a belt, maybe adjust the timing a bit if you were ambitious. Nowadays with electronic ignition and engine management systems you don't want to touch the thing without a masters degree and $20k diagnostic tool. But that's what they needed to do to push out the price/performance curve. And while the NRE on these things is huge, it's just insignificant in the context of global scale manufacturing.

A battery is no tan engine with moving parts. A very mature technology older than gasoline piston engines. The first cars were EV's before as engines were around. Edison planned to corner the market with his NiFe battery. There is no longer lasting, more expensive PIA battery than NiFe. Ask Mike. But few would ever use them.

[Sunking]

Tehan Lithium batteries can burst into flames, that is the main reasons some EV's use Liquid Cooling, Granted it can be used to extend battery life in mobile applications, the primary reason is safety. Tesla Roadster or anything using Colbalt is especially risky, thus why Lithium batteries have such a bad nasty reputation.

But in a home application, you are not pushing the limits of compact cramp spaces, extreme environments, and 10C discharge rates. Cobalt is also the most expensive and shortest cycle life of the family. Non eof that is a requirement in a home system, unless you cram 10 pounds of crap into a 1 pound box.

You certainly would do that in a telephone office. Nope you put them in a nice large ventilated room kept at 75 degrees for their whole life. Ask an RC pilot or RC modeler about lithium batteries? We have to charge them in special boxes or fire proof bags. They are even known to catch on fire in flight or sitting there doing nothing just like a Boeing 787. How about you laptop in the over head baggage space o o ron your belt where the cell phone is clipped on to. . .