Tesla Powerwall

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Post by T1 Terry » Thu, 14 May 2015, 05:38

I seem to remember reading the guarantee after 10 yrs was to 60% capacity, so is the guarantee for the 7kW pack to deliver 4.2kW and still deliver this for 10 yrs...... it's all in how you say it and guide the listener/reading into making their own interpretation of what was actually said.

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Post by coulomb » Thu, 14 May 2015, 14:34

offgridQLD wrote: 60 cycles pr year what a joke!

I think that may be their example frequency of use - suppose you get five blackouts per month, that's 60 per year.

Presumably, if you use it more often, it will deliver more cycles per year. That's the thing with standby batteries - they are there "in case", and may never get used, or very rarely. So their utility is in the avoidance of rare but very bad events, like losing your servers in a blackout. Their utility in kWh per year could be terrible.
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Post by offgridQLD » Thu, 14 May 2015, 15:08

Or perhaps my question should be. What part of the design and component choice has limited the use of the (backup) battery bank to (occasional use)?

What part of the daily cycle bank has optimized it for daily cycle use?

Just the difference in battery chemistry between the two?

The emergency back up unit would be charged and held at something near 100% SOC all the time (as it needs to be full to ensure it's always ready to go ) Assuming people want to use it who don't have solar and just have it on a AC charger ready to go (with an additional AC/DC inverter). Wouldn't it be like a laptop then. They often suffer from incredibly short battery calender live due to them being held at 100% SOC all the time while on AC power supply.

I still don't see why you wouldn't just by the unit optimized for every day cycling as it can be used for both circumstances. (Perhaps only if you didn't have solar the occasional cycle unit would be better)

I'm with others sharing the frustration that the specifications and detailed information about the stationary storage units is so limited and a challenge to uncover. I think Tesla want a bunched of brain dead zombies with there wallets out to just join the Tesla band wagon no questions asked.

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Last edited by offgridQLD on Thu, 14 May 2015, 05:55, edited 1 time in total.

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Post by weber » Thu, 14 May 2015, 15:40

coulomb wrote:Presumably, if you use it more often, it will deliver more cycles per year.

Isn't that a tautology? Surely the point is, if you use it more often than "60 to 70 times a year" it will do it for fewer years. There may even be a warranty condition relating to that.

As Musk says at around 15:30, the standby pack (10 kWh NCA $3500 $350/kWh) only has a life of 1000 to 1500 cycles, compared to about 5000 cycles for the daily-cycler pack (7 kWh NMC $3000 $429/kWh). But they both have calendar lives of about 15 years (although the warranty period is "a bit less than that").

So, like the choice between types of Araldite (low strength versus slow setting) you have a choice between Powerwalls (low cycle life versus low energy). Image And that's lower energy per dollar too.
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Post by offgridQLD » Thu, 14 May 2015, 15:52

Ok so when you say "low energy" I amuse the (7kwh daily cycle) bank is limited in it's max output rating but the (10kwh occasional cycle) bank isn't so limited in its max output?

Whats the limits on the occasional use banks output? If there allowing you to ring it's neck and draw 5C from it then I can understand it's limited cycle life quoted. As your potentially using it like you would in a EV. But if they are restricting it's output to something like 0.3c max like they are with the 7kwh unit then that's just very average cycle life numbers they are quoting.

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Post by weber » Thu, 14 May 2015, 16:06

offgridQLD wrote: Ok so when you say "low energy" I assume the (7kwh daily cycle) bank is limited in it's max output rating but the (10kwh occasional cycle) bank isn't so limited in its max output?

No, I didn't mean that at all. That would be confusing energy with power. As far as I can tell from the limited specs available, they both have exactly the same power limitations (2 kW continuous 3.3 kW peak) which I'm guessing is enforced by having your only access to the battery be via the DC-DC inverter[sic].

And yes, I think the only difference is the chemistry.
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Post by offgridQLD » Thu, 14 May 2015, 16:23

Ok so the 10kwh bank has no benefits over the 7kwh model other 30% more storage capacity. Though costing 15% more it perhaps only has 15% more value rated storage capacity due to the 15% cost hike over the 7kwh.

I think the 10kwh bank is dead in the water. Low output rating and low cycle life.. Not great selling points Image

Multiple 7kwh units (due to the limited output) or the larger commercial units are the only options I see that have any real value.

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Last edited by offgridQLD on Thu, 14 May 2015, 06:33, edited 1 time in total.

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Post by weber » Thu, 14 May 2015, 16:50

offgridQLD wrote:I think the 10kwh bank is dead in the water. Low output rating and low cycle life.. Not great selling points Image

And yet the low cycle life 10 kWh unit is the only one that Solar City are offering so far in the US. Presumably people just want a solar UPS for if the grid goes down. But surely they're going to need an "incremental" inverter for that, since your standard grid-feed inverter won't work standalone.

Musk mentions that the daily cycling 7 kWh unit makes more financial sense in Australia because of our different (Edit: electricity] pricing structure.

BTW, there is a way in which the term DC-DC "inverter" can make sense, although it's a meaningless (and confusing) distinction from the customer's point of view. The DC-DC converter may be of the non-isolating buck/boost type in which the output has the opposite polarity to the input (relative to the common terminal). This is completely irrelevant when the battery is floating relative to earth.
Last edited by weber on Thu, 14 May 2015, 10:48, edited 1 time in total.
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Post by Johny » Thu, 14 May 2015, 17:04

I think the DC-DC is just a reasonably wide range buck/boost converter doubling as an MPPT controller. They state it interfaces directly with the panels.
A few inverter manufacturers in the US are developing, or have developed, what they call "hybrid" inverters so they are both grid tied and standalone in the right configurations. Installation of these system would be quite costly IMO.

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Post by Richo » Thu, 14 May 2015, 21:00

$3500USD for 10kWh

So add say $350 for shipping = USD$3850
Convert to AUD = $4800
5% duty ($240) = $5040
Add dist margin (15%) = $5800
Add GST (10%) = $6380
Add installtion fee ($220) = $6600

10kWh of chunderskys are ~$5500
Surely for ~$1k you could buy most of the other junk to equal a powerwall.

Is it the white molded plastic case that sells it?
So the short answer is NO but the long answer is YES.
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Post by Gabz » Thu, 14 May 2015, 21:20

it comes in special colors !!! http://www.theverge.com/2015/5/1/852771 ... usk-colors

I'll be at Australian energy Storage in a couple weeks and have a look what the rest of the market has on offer.
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Post by mikedufty » Thu, 14 May 2015, 23:06

Received a marketing e-mail from A Woman's Spark today claiming they will be around $4,000 to $5,000 installed here.
I have apparently "reserved" one by following the link below. I wonder if that is what their claimed pre sales are based on .
http://www.teslamotors.com/powerwall

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Post by Richo » Fri, 15 May 2015, 21:03

http://www.theverge.com/2015/5/1/852771 ... usk-colors

OMG Image A writeup that ONLY talks about the powerwall colour.
Reminds me of those car ads on TV aimed at women!
Gabz wrote:
I'll be at Australian energy Storage in a couple weeks and have a look what the rest of the market has on offer.

Wow that looks pretty good except it's in the wrong state Image
AND Varley are going to be there - they'd be worth a talking to since they disappeared off the grid a year or 2 ago.
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Post by gmacd33 » Mon, 18 May 2015, 22:45

Hi Richo, what is "dist margin" for importing purposes?
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Post by offgridQLD » Tue, 19 May 2015, 15:22

I was just having a look through Calb's webpage. In particular there ready to go stationary storage packages and Ev traction packs.

They seem to have very modest specs for there own 200ah 10kwh system . around 0.3C discharge limits and about the same for there charge limits.
http://en.calb.cn/product/show/?id-644

Similar modest specs for there telecommunications package 400AH 48v around 100A limits.
http://en.calb.cn/product/show/?id-642

Then you have there EV traction pack 66AH - 20kw. Again reasonably modest performance numbers given (though not to bad). 30kw continuous(1.5C) 55kw max around (2.5C)

http://en.calb.cn/product/show/?id-634

So what to make of the first two stationary storage packages. In comparison to what Tesla are offering. Why so modest input - output limitations? This is a product designed by the cell manufactures them self. Why so conservative?




Kurt


Last edited by offgridQLD on Tue, 19 May 2015, 05:24, edited 1 time in total.

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Post by Gabz » Tue, 19 May 2015, 15:39

gmacd33 wrote: Hi Richo, what is "dist margin" for importing purposes?


probably a mistake since tesla will sell direct to installers in Australia it'll be installer margin not distributor. also tesla will reduce the duty on importation by writing down the cost of the pack.

by the way tesla are looking to employee a powerwall sales head in Australia already.
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Post by Richo » Tue, 19 May 2015, 20:50

Yeah distributor/sales margin.
Someone here will want a slice of the pie.
What would be the point of selling something for no profit...

There are heavy penalties for providing inaccurate info for customs purposes.
$4800 goes out $900 of product comes in gives bad Karma Image
And I'll tell you now they wont go chasing Telsa but Installer Joe Shmoe.
So the short answer is NO but the long answer is YES.
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Post by T1 Terry » Wed, 20 May 2015, 00:49

Richo wrote: Yeah distributor/sales margin.
Someone here will want a slice of the pie.
What would be the point of selling something for no profit...

There are heavy penalties for providing inaccurate info for customs purposes.
$4800 goes out $900 of product comes in gives bad Karma Image
And I'll tell you now they wont go chasing Telsa but Installer Joe Shmoe.

Not too sure about there being no point in selling without a profit, well as far as Tesla are concerned. They need an outlet for the Mega Factory battery production and they want to increase their exposure to the market they want to sell in, house battery systems. If Nissan sells their vehicles at a loss to gain market share there is no reason Tesla wouldn't do the same, at least until they crush the smaller start ups.
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Post by lopezjm2001 » Tue, 02 Jun 2015, 21:10

There is a Australia Energy Storage Conference and Exhibition tommorrow and the day after at the Australian Technology Park, Sydney.

http://www.australianenergystorage.com. ... workshops/

Free entry to the exhibition, just register on entry.
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Post by reecho » Tue, 02 Jun 2015, 22:08

I have 5.2kw of solar panels split into 2 strings in a NE/NW configuration. So about 2.5kw each string. 2 of the 7Kwh Powerwalls would be a perfect match. The question will be if they will connect control wise to my SMA 5000TL inverter.

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Post by reecho » Tue, 02 Jun 2015, 23:25

Looks like Panasonic is getting into the game in Australia too...

Panasonic LJ-SK84A

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Post by T1 Terry » Wed, 03 Jun 2015, 04:25

reecho wrote: Looks like Panasonic is getting into the game in Australia too...

Panasonic LJ-SK84A

The same silly limitations though, 8 kWh capacity, great, 2kW output... WTF?? So you need to parallel at least 3 of these things to get a worthwhile output, but do you need 24kWh of storage?
a 48v system using prismatic cells would only require 12kWh of capacity to deliver the same 6kW output at a lazy 0.5C discharge and have the capability of delivering 36kW peak short term if required, or 6kWh hrs for a peak of 18kW and constant 3kW and medium term 6kW delivery.
Is the limitation the small cylindrical cells they are using, or is it that they plan to dump their seconds via this marketing ploy as suggested previously?

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Post by offgridQLD » Wed, 03 Jun 2015, 04:39

"but do you need 24kWh of storage?"

Perhaps not if you just want to load shift a little over night.


24kwh of storage isn't that much. Sounds about perfect for a the avarage modern home if your off grid.

I have about 21kwh and wouldn't Want much less.

Kurt


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Post by mikedufty » Wed, 03 Jun 2015, 06:32

Load shifting is what they are marketing them for, isn't it? Not off grid, which means you don't need 24kwh, but also probably means you don't need more than 2kW, as that should be plenty to utilise the 8kwh of storage you have each day.

And if you did go off grid, you probably would need the 24kwh, so would get the 6kw.

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Post by Johny » Wed, 03 Jun 2015, 15:55

It looks like the Panasonic has everything included, inverter etc. Grid-tied and backup mode for essential appliances.
I'd love to know the price. Anyone?
Last edited by Johny on Wed, 03 Jun 2015, 05:55, edited 1 time in total.

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