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MSEE, PE -
Maybe for now. I doubt there will be high volume of Powerwalls manufactured before 2017. There should be one or two quality competitors by then, probably using different lithium formulations. It's not a good PR move for him to have people complaining about their Solar City quotes. Prognosticators had the powerwall costing $13,000 too.Comment
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You heard what you wanted to hear. From Chief Technology Officer JB Straubel said that the Powerwall is a 400 volt battery that "doesn’t use heavy gauge wire, so that makes the installation easier and faster"
He is absolutely correct operating at 400 volts pumping 2000 watts only takes 14 AWG wire with 5 amps ran in conduit.All you need is $7000 and you can have one too.Now all you need is the Tesla Hybrid Inverter to make it work.MSEE, PEComment
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Concerning the 14 wire, he could have been talking about the interconnects between multiple units. They also said the powerwall works with some existing solar city installed inverters.Comment
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Guess who sits on the Board of Directors at Solar City and majority stock holder? Can you say Elon Musk? Solar City has exclusive rights to the Battery. You cannot touch one for less than $7000 just for the battery. Want equipment to work with it? That is extra and Solar City has to sell it to you and install it.MSEE, PEComment
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Yeah, for their new line that Sunking likes (e.g. the IND9-6V), it's free replacement to 3 years, then prorated to 8 ( http://www.trojanbattery.com/pdf/TRJ...edWarranty.pdf ).
And according to http://www.trojanbattery.com/wp-cont...n_Overview.pdf they
are unlike most FLA's, and don't mind it if you don't charge them fully.
They're not for people who can't do this:
but they are real. I'm looking forward to seeing some whole-system writeups
showing examples of where they pay off in real life.Comment
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In the presentation Musk says "it has....the dc to dc converter". Then he says it is designed to work with existing solar systems.
I suppose he could be talking about the charge controller taking a range of voltages. But he used the term "converter".
Coming out with 400v dc would make it easy to parallel the system. But then they have to build many sizes of inverters to work with 2000 to 18000 watts. I have a hard time seeing Musk or solar city wanting to be in the inverter business.
I get using a 400v bus on the utility side of these products. It seems non-standard to expose that in the residential business.Comment
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Why not?
Standard dryer outlet is 240V AC (peak-to-peak voltage of ~680V)
Most US solar installations have between 300 and 600V DC
There are even high voltage DC car chargers. I'll grant you that they're not common in residential, BUT they are setup so they're safe enough for any idiot to make that final connection between the high voltage DC supply and the car.
From an installation point of view, doing 400V tied to the house wiring isn't any more difficult than doing 48V - it's probably simpler because of smaller gauge wires. The expertise needed to deal with >50V is already needed for doing the 240VAC side of things. So it's not like you need an electrician where you wouldn't have before.Comment
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I agree with you fully up to this point I take some difference. Moving from 48 volt to 51 volts all the rules change as you cross the 50 volt nominal line. When you cross that line you are now required to use a Grounded System where with 48 volts you can Float or run a Grounded system. But more importantly is everything now has to be enclosed and wiring in protected raceways and absolutely no live exposed parts with no access ti live parts of the system. In a 48 volt battery system you can have the batteries mounted on a rack and cables ran in free air where you can easily access the batteries. Cross that 50 volt nominal voltage line and every thing changes.
Other than that you seem to have a grasp and understand the benefits of higher working voltages. The catch is if you use the Tesla system. Absolutely no DIY or user supplied equipment. Tesla has the whole process locked down and under his controls and rules of engagement. That is what I have a problem with. That so called $3000 to $3500 price tag is completely BOGUS. Sure it will show up as $3000 on a line item in the finale bill. Classic Bait and Switch and not a darn thing the consumer can do about it.MSEE, PEComment
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First 400 Volts is not Facility Side. Facility is 240 VAC in Residential end of story. 400 volts is CPE (Customer Premises Equipment) side and not at all uncommon with grid tied systems as they operate from 200 to 500 volts using String Inverters. It is everyday practice. However String Inverters are Current Source Invertrs not Voltage Source aka Battery Inverters. There are Hybid Inverters out there made to work from either panels or batteries. But all those are 12, 24, and 48 VDC architecture. No problem making a Hybrid Inverter to operate at high voltage as it is easier and less complicated to use 400 volts vs 12, 24, or 48 volts. But to my knowledge they do not exist. It appears Musk has an answer with another product line from another company he has partnered with Solar Edge. Smart, very Smart when you see the whole picture.
As for the Converter statement I have learned Tesla has working prototypes in a Walmart as a UPS set up, and a few high-end homes with Grid Tied Systems have the system installed. There is no mention of any converters used. Only thing pointed out is the Walmart UPS uses 480 VAC 3-phase input to the chargers. In the Specs Tesla clearly states the units do not come with with an Inverter and is silent on any DC - DC Converters. My educated guess is since the units are made to be Cascaded the DC to DC Converter if it exist is a Add-ON based on how many units you Cascade. But to do it that way is another Egg in the basket to break and eat into efficiency. It can be done that way especially if you intend for your product to be proprietary which so far everything Tesla does is proprietary. No one has access to the batteries, controllers, motors or anything Tesla uses in their vehicles. Proprietary = Big Buck$ and profit margin. Again very Smart.
Based on that knowledge and knowing Musk is one crude sharp businessman he is building a very high end proprietary RE energy platform as a spin off and making a customer out of a $5 Billion dollar battery factory we tax payers are paying a portion of. That is the exact same business model Tesla Motors uses. They build high-end EV's for an elite crowd where price is no object. Just as long as it makes you fell Green and ignore the details. I am the first to admit Tesla makes a damn nice EV a cut above all others. What i despise is the deception and using TAX PAYERS money to build the damn things, and forced again to pay for Charging Stations. Dang it if you can afford such luxury, pay your own damn bills. Same with Solar, pay for it without our help and take whatever the electric company is wiling to pay you for excess. They don't need or want the power. It is the poor and working class paying for it, not the user.MSEE, PEComment
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Since it'd be a fully contained unit for the batteries and a fully contained unit for the inverter, the only extra thing to have a 'protected raceway' is potentially the connection between the two.
What part of NEC are you basing the requirement for a protected raceway on?
If that is a requirement based on NEC, then I think it'd be satisfied by just putting a conduit between the battery bank and the inverter. And likely they'd be installed basically side-by-side, so conduit between them probably would be short.
Since it's a pre-packaged unit, the "cables ran in free air" thing my not be allowed, but wouldn't matter. The cell/battery interconnections wouldn't be in the free air anyhow.Comment
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