Tesla House Battery / Utility Scale Battery

[woodgeek]

Here's another link, with the fun 18 minute presentation embedded.

http://insideevs.com/tesla-reveals-battery-storage-solution-missing-piece/

I recommend the video. Elon is a bit of a nerd, but solving climate change just became sexy, fun, and an excellent investment opportunity.

Its clear that the two products...7 kWh and 10 kWh have the same footprint, and IMO likely the same physical battery. The 7 kWh is intended for daily cycling, and prob only charges the cells from 10% to 80% SOC (thus 70% of nominal capacity), but with (low charge discharge rates, below C/5) the hopes of getting say 2000-3000 cycles (i.e. 10 years on a daily cycle). The other unit, intended for backup, allows you to use the full SOC, but limits you to a 'weekly'/backup cycle application, or about 500 nominal full cycles in 10+ years.

So, if you were going off grid, you would have to go with the 7 kWh version, gang them together until you got the bank size you wanted, and then have a zero-maintenance, XXX year warranty system in place.

If we figure the 7 kWh system is good for 3650 cycles (10 years, diurnal) and ran the full 7 kWh delivery, that is 13.7 cents/kWh upcharge to store your power in an off-grid system. I think this (if it comes with a 10 year warranty/ performance guarantee) is competitive on price with existing solar off-grid applications, and is VERY competitive on space/maintenance ground, and hopefully on reliability as well.

The 13.7 cents/kWh rate will be competitive in Hawaii today, and that market could presumably absorb a lot of the first year 'ramp' of production.

As for profits? If Tesla is currently costing ~$250-300 /kWh for its cells, then the 7 kWh system (10 kWh actual) costs $2500-3000 for the cells. Not leaving much for the balance of system inverter, controller, housing etc. I don't see a huge profit margin here...but they could be close/negative on costs today, and still project a decent profit when they open the spigot in a year or two (with $150-$200/kWh cells).

 

[JP11]

I can't quite wrap my head around the differential. but let me try.

If I went to 'time of use' billing on my house. and I use 1000kwh in my house (that's a close average back when I was using oil heat, big house,and an attached business)

so. that's 150 dollars of power at my 'standard rate'

If I went to time of use.. and got ALL of my power off peak.. that's 97 dollars. Peak rate it would be 183.

So I've saved 53 dollars per month. 636 per year.

That's 5.5 years to pay off the 3500, not including install. How many years do you say it would last?

Not all decisions are dollars and cents.. but this one seems just a bit out of reach FOR ME.

JP

 

[woodgeek]

First off, whomever found an 18650 LiIon cell with a 4Ah capacity - give me a link Most of the ones Ive seen (we use them in hobby applications) are 2.6Ah... sometimes 3.

But that doesn't matter, since 18650 are very small format cells - they are laptop battery cells. For a large off grid battery it would be better to use larger format individual cells so you dont have to string as many of them together. Trying to make a many kilowatt pack out of little cells you end up having a large % of the mass, volume and cost of it go to the metal in the cell cans , packaging and interconnect wiring... a waste.

As far as cycle lives go, I'd be really impressed with a LiIon that actually manages 1000+ cycles. When used hard, LiIon is more like a couple hundred until noticeable capacity loss is evident - Im sure we have all experienced laptops and cell phones that wont hold a charge in as little as 1-2 years. A123 Lithium Iron Phosphate's are probably the leader in this regard, doing an honest 1000+ at very hard discharge rates, but they are very expensive, even compared to already expensive LiIon. Again, Lead Acid is still the value leader here, good cells can manage close to 1000 cycles but it comes at the cost of low discharges -even for good flooded deep cycle off grid batteries like the Rolls Surette pictured above reaching those numbers means limiting to 40% discharge depth. If you go for 80% the life cuts in half.

Great info, Jeremy.

The bigger 18650 cells if I recall are a 'special product' made by Panasonic for Tesla. Tesla claims that the cylindrical form factor is cost optimal, since the fabrication is readily mechanized. They also claim that in EV apps, the small cells facilitate thermal management in high charge/discharge rate. The assembly of cells into banks is also robotized if I recall. They also put a fusible link on each cell, which makes the bank fail-safe if one cell should come up with a short. (Too bad Boeing is not buying these for APUs).

As for Li-ion cycles, it comes down to the charge controller. Certainly a lot of cheaper electronics have bad controllers and short battery lifetimes (do you need a windows laptop to run longer than 3 years?). Case in point, all my Apple laptops have managed >1500 cycles (counted on a full discharge basis) with only a negligible capacity loss, including the ones made 10 years ago. If Elon thinks he can baby his cells (C/5 or lower, 10-80%SOC) and get 2500-3500 useful cycles (as implied by the calcs above), then I believe it.

 

[woodgeek]

I can't quite wrap my head around the differential. but let me try.

If I went to 'time of use' billing on my house. and I use 1000kwh in my house (that's a close average back when I was using oil heat, big house,and an attached business)

so. that's 150 dollars of power at my 'standard rate'

If I went to time of use.. and got ALL of my power off peak.. that's 97 dollars. Peak rate it would be 183.

So I've saved 53 dollars per month. 636 per year.

That's 5.5 years to pay off the 3500, not including install. How many years do you say it would last?

Not all decisions are dollars and cents.. but this one seems just a bit out of reach FOR ME.

JP

Your numbers make sense.

1. I do not think this product makes sense in 99% of US applications. But I think for 1% of customers, most of whom have solar already, there can be a good value proposition.

2. It also puts a 'cap' on grid energy costs before you would 'defect'. If the current PV off-grid electricity costs are seen as $0.50-0.75/kWh, depending on seasonal needs for battery storage (less needed in HI or CO than ME), Elon just dropped the cost of going off-grid in the more favorable locations by 20 cents/kWh or more, and made it 'effortless' and sexy.

3. In my HCOL area, folks are happy to pay $20k for an automatic backup genny. How many would rather pay $10-13k for a 30-40 kWh bank of 'powerwalls' that can run their house for a day or two (if they have fossil heat), and the difference in cost pays for a lot of hotel rooms for longer outages. IMO, the 'backup market' could be as big as the 'off-grid solar' market.

 

[JP11]

I agree.. in a remote setting this could be a great part of your system..

solar
battery
genset

when you're forced to run your generator, you can store your excess production. I imagine that SOME that are off grid have already come up with a solution like this. If elon can make this an 'iPhone' simple system.. more power to him. I think it would be very cool, and could be the beginnings of a 'smart grid' for remote areas.

as this tech is adopted though, lets say in a mythical island. Those that are disconnecting from the grid will only make costs higher (economy of scale in reverse) for those remaining connected. This will make this tech even more appealing as prices per Kwh rise.

JP

 

[woodgeek]

To folks in Maine, Hawaii might seem mythical, but its a real place!

 

[DougA]

Musk reminds me of Steve Jobs. A whole lot of fanfare & hype to show off something that is a snazzy version of stuff we can already buy cheaper. I've done the math multiple times and I cannot justify the cost of this or any other battery system to untie me from the grid. The payback is far too long, even calculating in the future increases in hydro rates. In my case, you are either on the grid or not. Reducing power usage does have some effect but our hydro rate is one half of the total bill and the 'extra surcharges' are what is the killer. Today, I'll be using $25. in energy coupons to buy more LED lights to replace the last of my old bulbs. That $25. is not free, someone else on the power grid will pay for my savings. Tomorrow, I'll have to pay for someone else's. Coupons like that are BS and I hate that.

The one good thing about this announcement is that it takes all of us one step closer to power independence. Not close enough for 99% of us, but it will come eventually.

 

[woodgeek]

Musk reminds me of Steve Jobs. A whole lot of fanfare & hype to show off something that is a snazzy version of stuff we can already buy cheaper.

Sorry, where now would you buy a cheaper 10 kWh Li battery bank for residential backup use? I don't even know of any 'turn key' lead-acid systems that size.

 

[jharkin]

I agree.. in a remote setting this could be a great part of your system..

solar
battery
genset

when you're forced to run your generator, you can store your excess production. I imagine that SOME that are off grid have already come up with a solution like this.

Thats exactly how off grid folks build their systems.

First they size their battery back. Knowing that there is always going to be cloudy days they figure the average ratio of sunny to cloudy days and size the bank for a reserve to run when the cells are not producing. This varies but I think 2-3 days is typical. The cells are sized to cover that many days to 50% DoD.

Then they size their panels to be able to recharge the bank at 50% DoD in a reasonable time span. I think 1 day of good full sun is used. (this means that the panels end up sized to produce more than the house uses per day when its sunny)

Then they add a small generator for backup for the occasional long stretches of bad weather. The generator is used to charge the batteries, not power the house directly - so it can run at full load max efficiency. Often diesel or natgas generators are used to avoid fuel storage concerns.

 

[DougA]

Who says you need turn key? How much effort is involved in wiring together some lead acid batteries? Gee, sounds just like Apple that wants to charge twice the price for 'packaging' a sexy looking system.

EDIT: for got to add that AFAIK, this unit is not turn key. It still needs an inverter to run appliances - at least according to news reports and that will up the price A LOT.

 

[JP11]

There's always someone willing to pay for 'plug and play'

 

[jharkin]

Sorry, where now would you buy a cheaper 10 kWh Li battery bank for residential backup use? I don't even know of any 'turn key' lead-acid systems that size.

10KWh is not that big to do with lead.. You could get away with just 2 of these But the 4 volt series voltage would be to low to be practical.

http://www.solar-electric.com/batte...s/suprdecyba/2voltbatteries1/suba2vo24am.html


Better option would be 4 of these 6 volt batteries for 10,300 watt hours @ 24 volt series voltage. $1200 for the batteries plus wiring and charge controllers. That's 11.7 cents per watt-hour maybe 20-25 cents once you add in all the wiring, charger controller, inverter and installation.

http://www.solar-electric.com/batte.../rolls-surrette-s-550-deep-cycle-battery.html


EDIT - Big goof, for lead you only use 50% DoD so this owuld be doubled to give 10KWh usable. Making the figure more like 25-50 cents per W-h installed.

 

[woodgeek]

Who says you need turn key? How much effort is involved in wiring together some lead acid batteries? Gee, sounds just like Apple that wants to charge twice the price for 'packaging' a sexy looking system.

EDIT: for got to add that AFAIK, this unit is not turn key. It still needs an inverter to run appliances - at least according to news reports and that will up the price A LOT.

Time will tell. I thought the inverter was built in (and only 2 kW_peak per module), crazy not to since its part of battery management...a bad inverter could kill the thing.

Re price. I agree that good AGW batteries are easy to wire and maintenance free...and cost the same or more per kWh*cycles as this thing. You can beat the price on flooded cells (I think, more like $100-$150/kWh), but then you have a lot of acid slinging maintenance. There is a reason most off-gridders go for warrantied AGW...but I think Tesla has clearly beaten the AGW on 'lifecycle' cost per kWh stored.

If Tesla only has a 2 yr limited warranty, then I'm with you Doug! I expect it will be more like 7-10.

 

[woodgeek]

Jeremy, what is the cycle rating/warranty on the surrettes? And converted to a 100% SOC basis...as in rated kWh out over the life of the battery? Converted to a $/kWh_delivered??

 

[jharkin]

Jeremy, what is the cycle rating/warranty on the surrettes? And converted to a 100% SOC basis...as in rated kWh out over the life of the battery? Converted to a $/kWh_delivered??

good question.. I looked it up, they warranty for 5 years pro-rated, 2 years full replacement on batteries used in off grid.

Oh and I knew I must have made a mistake. In my calcs above to get 10KWh of usable capacity the lead bank would be sized to 20KWh. So my example above would actually be 25 cents/watt for the batteries. Probably 50 cents per watt instaleld with wiring, chargers, inverters. Still seems a lot cheaper than the $1.30 a watt quoted at the top of thread.

disclaimer - Ive never done one of these, just getting my info from solar forums and the battery MFG webpage.

 

[begreen]

As far as cycle lives go, I'd be really impressed with a LiIon that actually manages 1000+ cycles. When used hard, LiIon is more like a couple hundred until noticeable capacity loss is evident -

The key here seems to be to control the rate of depletion and limit it to avoid full depletion. Electric car LiIon batteries do this with maybe an average of 300 charge cycles a year, or more for a daily driver like a Prius taxi cab. Our 7 yr old Prius battery was showing no sign of exhaustion when we sold the car. The Volt and Leaf batteries are warranted for several (8 and 6) yrs..

 

[Clarke]

This looks like a great unit, but how would I install a 300V battery into an existing 12, 24, or 48V system?

 

[begreen]

I am wondering how they do the grid-tie interface too. My guess is that it is post solar inverter. If so I would suspect it to be managed as a feed to the battery pack charger.

 

[Clarke]

That sounds right, but it would make for a very complicated retrofit for those of us who run DC charge controllers (solar, hydro, wind) and have no grid to tie into.

 

[jharkin]

Regardless of the difference in voltage, the LiIon cells also have a different charging profile than an existing 12/24/48v lead acid system so there would have to be a separate charger fed by the output of the solar cells.

 

[DougA]

Not to go too far off topic, but I'm way more interested in finding a way to convert heat from my wood stove into usable electricity. The Thermoelectric effect (Seebeck/Peltier) has far more potential for us wood stove users. I've got a fan that sits on my stove that gets all of it's power from the heat so why can't this be ramped up to charging a battery at night and using solar during the day? Both are free - at least for us stove/furnace people.

 

[Clarke]

Luckily, all of my charge controllers, and my inverter/charger are configurable for the LiIon charge profile. Maybe I could find a massive buck converter. Joking. Unless Tesla has some further ideas, or models in the works???

 

[Clarke]

Check out e-bay. there is quite a selection.

 

[JP11]

Here it is.. Stirling Engine. BIG money.

(broken link removed to http://www.energymanagertoday.com/biomass-boiler-stirling-engine-heats-water-generates-power-0109653/)

I found one in MI I believe it was. Natural Gas input. Power and heat output. Something like 50k BTU and 5kw energy. 40 grand!

 

[jharkin]

TEG's have been discussed before.. They are expensive to make and the efficiency is so (5% ish) low taht even if you could build one to capture a majority of the heat output from your woodstove the electric output would be tiny.

For example, say your stove is outputting 30,00 BTU/hr
Thats 9500 watts of heat energy.

If you can capture all of it with a TEG you would get an electric output of under 500 watts.


And thats best case, assuming the stove is cranking full blast all the time and the TEG is very large.