SolarCity Corp Offers Tesla Motors Inc Powerwall Battery For $5,000

I'm not sold just yet.

It all looks good on the internet site.

And we all know that if you see it on the internet, it must be true.

What happens if Solar City goes the way of Solyndra in 5 years?

I'd be very interested to hear what energygod thinks about all this. He's the best source we have as a member, I believe.

Good observation, Solar City has not made a dime and does not pan to till 2018, this is on their web site if you dig deep enough. I am thinking of hiring them to install panels here, but they have to be on my frames that follow the sun. Waiting for an answer of off roof system. Has to be land based to follow the sun. So far no word, been 4 weeks since first contact. Will update if any answers.

I think its a bad move for Tesla, Musk went "all in" on a 5 billion dollar battery factory. Many others have been working on battery tech a long time, GE, Siemens as well as MIT, Stanford, etc are on the verge of new technology. if a competing battery is introduced......and I expect it will as Musk develops this market the 5 billion investment might be quite over extended. also. the pack is 3500, then installation. you charge it during the night at a lower rate then use it the next night when rates are steeper, you save 25%. so if you save 350 a year the payback is 10 years...right about the time the warranty is winding down, its a gamble that only has a small upside for the consumer

I agree. Unless the payback period is around 3-5 years, it is not economically worthwhile. Let's say 4 years: a 25% return on capital sounds good, but it's on a depreciating asset. Rather like investing in a stock that pays a fat dividend, but is headed for bankruptcy. Unless the underlying system is good for 10 years or more, then it's hard to get excited. Every system has risk - failure, breakdowns, superseded by better technology, loss of capacity etc. You need to be well recompensed to take on such risks.

This is a partnership with Solarcity to reduce the costs of solar energy for the consumer...Yes they can be used as UPS, but that is not the ultimate goal...probably only worth it if your power supply is unreliable, or you're a large enough energy user to leverage the off peak cost of storage and resale during peak in certain markets...

"Although Solar City has only one small factory so far, it's negotiating with New York State and potential partners to fund one about as big as the largest one in Asia. Rive says he plans to follow this with factories 10 times as large. At such a scale, assuming solar cell efficiencies can be steadily improved, the cost for installed solar panel systems would be cut by about half, from $2.30 per watt to $1.20, Rive says.

At full capacity, the battery factory that Tesla plans for Nevada would eclipse all of the current lithium-ion battery production in the world. Musk believes his factory will help lower the cost of batteries to less than $100 per kilowatt hour of storage-down from what analysts estimate is about $300 now.

Solar City only decided to get into the business of making solar panels, instead of just installing and maintaining them, this year. In June it bought a startup called Silevo that has technology that improves the efficiency of silicon solar panels without complicating manufacturing (see "Startup Silevo Scales Up Even As Others Shut Down")."

23% efficiency...

http://optics.org/news/5/6/24?utm_source=rss&utm_medium=rss&utm_campaign=solarcity-aims-big-with-silevo-acquisition-optics-org

Solar city IS Musk and his cousins

Solarcity is a publicly owned company....Elon Musk and his cousins just run it....

Vice is nice, but incest is best.

Uncle Daddy!!

It makes sense that Elon Musk wants to push into new markets to drive down prices through economies of scale. What is harder to understand is how lithium ion batteries are going to compete with lead acid in an application where the big advantages of lithium ion batteries don't count.

If these batteries are targeted for use with residential solar especially if the goal is going off grid, then there is no need for rapid discharge (16 to 20 hours or more would be expected), there is no benefit for lower weight per KWH other than initial shipping/installation, ventilation and temperatures shouldn't be a problem, and smaller size won't make much difference in most cases.

Proper charging management and purchasing enough lead acid capacity for low discharge rate per capacity and low depth of discharge (probably around 30%, but definitely less that 50%) to insure efficiency and long battery life, would be essential.

That shouldn't be hard to do and still come in below the 500$/KWh at which the Solar City/Tesla battery is being priced.

Sounds a lot like the problems you attribute to lead acid batteries are whole attributable to insufficient installed capacity.

Yes, reducing depth of discharge typically garners large benefits in longevity and robustness of the system. Over the long term adding more capacity up front will result in fewer batteries bought over the long term. Still, reducing depth of discharge doesn't really follow as an answer to insufficient time to a complete proper charging.

Having more than one bank with the necessary capacity is a good idea to allow more flexibility for completing proper charging. Note that even though more capacity if needed to install more than one bank, it doesn't actually benefit depth of discharge.

Also note that bringing batteries to 100% state of charge needn't happen every charge. There shouldn't be any degradation if the batteries are regularly brought close, and then brought to 100% every week or so.

Your cost figures for lead acid and lithium ion battery capacity seem high by at least an order of magnitude. Also, while it is possible to skew the comparison by using short discharge times and minimal capacity to make lead acid look more expensive than lithium ion, that would be a foolish way to set things up.

You're right...My figures are inflated. I priced as 1kAh but typed kWh in error.

The prices shown relate to a 12kWh (1kAh @ 12v) bank not 1 kWh, the price per kWh in 2011 for LiFePo4 was around $2000, and for LA was $400 and is now around $500 for a decent battery.

The problems with LA batteries are almost always attributable to insufficient installed capacity as this affects the depth of discharge and cycle life which are the main causes of their early demise.

Adding more capacity up front doesn't result in fewer being purchased over the long term as LA batteries have a finite life even if treated gently. The generally accepted best economical sizing for LA banks is the 50% rule, where the cost versus usable amp hours is best where the battery bank is sized for a regular 50% DOD.

This is fine if you have a backup charging source, but you can't rely on solar alone for this.

Having more than one bank just adds to the cost and complexity of the setup.

I did say that full charging was required on a regular basis, if a lead acid battery remains in a discharged state for even a couple of days, sulphation will begin.

Consider that a 100Ah lead acid battery being discharged at the 0.1C rate (10 amps) will drop below 12v in a little over 4 hours and be flat (10.5v) in 9 hours, and a 100Ah LiFePo4 will go for about 9 hours to 85% DOD before dropping below 12v.

Let's look at a very moderate discharge rate so there is no skewing of the figures to make LA look more expensive.

A 12kwh LA bank supplying a continuous domestic load of 10 amps at 240v via an inverter would be at 50% DOD in just 4 hours, cycle life at this rate would be around 1100, a 12kWh LiFePo4 bank would supply that load for 9 hours for a similar cycle life.

So you would require twice the rated kWh of LAs for the same performance and cycle life, and as prices are now almost identical per rated kWh, the choice is pretty clear.

Technology will further improve for LIs but its finished for LAs, and economies of scale will further reduce the price of the Lithiums whereas Lead acid prices have been relatively stagnant for years.

Don't confuse LiFePo4 and its allies with other less stable forms of Lithium ion technology such as LiCoO2, and no, I don't have any stake in the product, just very impressed with them.

Those price estimates are much more reasonable. In fact, I think we agree on most points. Our respective tones are just different.

I agree with you that lead acid technology is unlikely to improve much and that lithium ion battery technology is improving as the price falls.

The only substantive thing upon which don 't see eye to eye is comparison of current cost of capacity. You state that the cost per rated capacity is about the same for lead acid and lithium. I have trouble squaring that with what I can find on the market.

Two quick clarifications:

First, the additional banks does indeed add complexity. It also adds flexibility for both longer charging times and maintenance.

Second, when I stated that buying additional capacity up front could result in less purchased over the long term, I was referring to the fairly ubiquitous trend in lead acid batteries for which a reduction in depth of discharge is more than off set by an increase in lifetime cycles....all other things being equal. This holds true pretty reliably almost until typical depth of discharge is only 10%, i.e. lifetime cycle expectancy for DoD limited to 50% is typically around twice that of DoD only limited to 80%. Similarly a doubling of lifetime cycles can be expected reducing DoD by less than 1/2, so around 30%. The point is, up to a certain point, cycles can be doubled without cutting depth of discharge in half.

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All of this assumes that there is no restrictive weight limit and that the batteries can be spaced well with good ventilation protected from extremes of cold and heat, and that proper maintenance and charging regimes are consistently used.

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Lithium ion batteries certainly have a lot of strengths, I don't think price is one of those yet, though.

I based my price for Lithiums on your statement "That shouldn't be hard to do and still come in below the 500$/KWh at which the Solar City/Tesla battery is being priced".

I had not read the article, but assumed your price was correct, so that was not far removed from what you would pay for a decent bank of deep cycle lead acids such as BAE or similar. Having now read the article, I see that they are offering a 10kWh pack for $3500 which I guess includes hardware, But even if not, that's just $350/kWh, and cheaper than most decent lead acids

Technically, "Cycle life" refers to the number of full discharge and recharge cycles that a battery can withstand until its capacity falls to just 80% of original, but it is also understood to include two half discharge/charge events to be one complete cycle, four quarter discharge/charge events to be one complete cycle etc., and while increasing the capacity of the bank will lower the DOD and therefore the number of complete cycles that the batteries endure by pretty much the numbers you quote, the fact remains that you have to purchase more batteries to achieve that. The 50% rule tells us that is not the best economical use of lead acid batteries.

ADMIN: Removed Resource

The linked article was removed because it is no longer on the host site.

The price I noted was the same as the one in the title of our comments $5K....for 10kWh. If lead acid batteries cost that much, definitely don't make the purchase. I wouldn't expect to pay more than 1/4 to 1/3 that price for lead acid batteries.

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Lifetime cycles: check out this graph.

http://www.mpoweruk.com/images/dod.gif

Note that cutting depth of discharge in half pays off with more than doubling the lifetime cycles. Any such advantage could be lost with aging if batteries are subject to high temperatures. ...but seeing as how we are talking about a home system, ample spacing and sufficient airflow should be built in initially.

If lead acid batteries are operated on the right hand side of hat chart, they don't look that great. In a similar light, a pair of tin snips seems like a lousy tool if I want to trim my toe nails.

I think i'll wait until they design a better battery, I've never had much luck with lithium-ion batteries. If you have the room, lead-acid is still the best option, in my opinion.

Really? Those are some mighty bold claims for something that can be constructed out of (relatively) easy to obtain materials (including scrap).

I think some of us here would be interested if you could elaborate on the matter (perhaps even a dedicated thread).

Without checking the math or knowing the capacity I am guessing the overall battery is going to be MASSIVE for a home power application!

There is a Wikipedia article on the subject....

http://en.m.wikipedia.org/wiki/Nickel%E2%80%93iron_battery

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As far as the size, these types of batteries were used for power in the V2 rocket and also in some of the early electric cars. That would indicate the size must not be absurdly large.

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Iirc, Jay Leno has an early electric car with one of these original batteries still operating...around a century old.