Tesla Motors Announces a New Home Battery • Hacker News Board

Re: Tesla Motors Announces a New Home Battery

#201

Post by brudgers » Tue, Feb 17, 2015, 8:00 PM UTC

SideburnsOfDoom wrote: post #44

brudgers wrote: post #23

So, where does lithium come from? It comes from the Earth, of course, but it doesn't require strip mining or blowing the tops off mountains like other resources do...most often, lithium is found in briny underground ponds. The liquid is pumped out and left to dry in the sun. TANSTAAFL https://duckduckgo.com/?q=lithium+pond+photos&iax=1&ia=image... Mining is mining. There isn't a "green" form. Tearing holes in the ear…

You can get energy out of a lithium battery several times, which puts it well ahead of tearing holes in the earth to mine coal. No, it's not permanently "off the grid" as it depends utterly on the whole industrial infrastructure, but it not continually tied to the grid like a power line running to a coal-fired power station.

TANSTAAFL.

You can't get any energy out of a battery until you put energy in ... alas more in than out per the laws of thermodynamics.

Re: Tesla Motors Announces a New Home Battery

#202

Post by brudgers » Tue, Feb 17, 2015, 8:02 PM UTC

warfangle wrote: post #199

brudgers wrote: post #187

Earlier quoted context omitted.

A couple of my architect friends -- and they are good competent architects who spend the proper portion of their fees to hire competent consulting engineers -- designed an emergency services center a few years ago. The hurricane came - the project was in Florida - the utility cut grid power per protocol and the automatic transfer switch didn't flip to onsite power. Neither did the backup automatic switch. The person…

> The person And there's the problem.

The HIL was the backup to the backup.

[HIL]: https://en.wikipedia.org/wiki/Human-in-the-loop

Re: Tesla Motors Announces a New Home Battery

#203

Post by msandford » Tue, Feb 17, 2015, 8:04 PM UTC

engendered wrote: post #197

msandford wrote: post #190

Earlier quoted context omitted.

You're right of course that it's not peak shaving, which is about shedding load. That was incorrect of me to state. But it is peak generation, which is just as valuable. > Again, no home battery pack is helping the power company. Please re-read my comment where I detail the economics of pulling power off the grid at low price and selling it back at high price is actually net-negative for the individuals doing so. Fro…

It isn't just as valuable. Again, the wholesale market rate is significantly less than the subsidized tariff that they pay homeowners to feed back. To your final paragraph -- you essentially made up numbers and then demand that I refute them. 10. 14. 1.3e12. Refute that. The single and only reason this side discussion even happened is that I noted that some power companies will refuse to allow grid feed-in if you ins…

Did you even re-read what I wrote?

Lead acid batteries cost about $100/kWh nameplate. But at 100% depth of discharge they wear out VERY quickly. We'll assume 50%. That means they cost $200/kWh in actual capacity.

At 50% depth of discharge a lead acid battery will only get about 1000 cycles before it's not very useful anymore and needs to be replaced.

$200 / 1000 cycles = $0.20 per kWh per cycle.

That's the fixed cost of a lead acid battery. Every time you charge and discharge it, you've lost $0.20 per kWh in terms of the capital cost of the battery. This has nothing to do with the price of power, but it has to do with the depreciation of the asset.

Okay so now let's deal with power cost. It's 14p to buy low, 19p to sell high. Since I'm in the US I'm going to convert that to dollars at the rate of about 1.5 which means that the MOST money you can hope to make on the arbitrage of low price to high price is $0.06

Now let us compare $0.20 per cycle of cost with $0.06 per cycle of revenue (again ignoring the fact that in reality nothing is 100% efficient) and we can easily see that this is a losing proposition. It'll lose AT LEAST $0.14 per kWh per cycle for the person trying to operate this arbitrage scheme as a business and they'll soon go bankrupt. Problem solved.

Now if the cheap power was $0.01 and the expensive power was $0.50 then they might be able to make money. But from what I understand of the power pricing, that's not the case.

If you'd like to continue to argue, please do so with actual numbers that mean something and/or are based on reality, rather than belligerent trolling. Please see this link where I previously did the analysis that you couldn't be bothered to read: https://news.ycombinator.com/item?id=9063702

Re: Tesla Motors Announces a New Home Battery

#204

Post by thinkcontext » Tue, Feb 17, 2015, 8:42 PM UTC

BurningFrog wrote: post #188

Tesla could offer an "attachment" to their cars that let them serve as a home battery when parked. You'd have to let it charge up before going driving, but for home owners who don't drive much, that could be very cost effective. Unless I'm missing some complication?

Batteries have a limited number of charge/discharge cycles. If you use your car to power your home you'll have to replace the batteries that much sooner, at a cost of $thousands. Electric car buyers are paying a premium to have the batteries be mobile, better to use them for that application.

Re: Tesla Motors Announces a New Home Battery

#205

Post by CapitalistCartr » Tue, Feb 17, 2015, 8:45 PM UTC

fredkbloggs wrote: post #195

CapitalistCartr wrote: post #102

I'd love to have a self-contained electrical system for my house. I'd preferentially wire my home with a DC grid alongside the AC, but there's no standard. Do I run 120v, 240v, 5v, 12v? Which interface do I use? Barrel connectors, USB, cigarette lighter? If we have a large-scale movement to household DC, we'd have these things hammered out without me rewiring every appliance. If these obstacles were overcome, almost…

There are standards, many of them, just as there are many different standards for AC power worldwide. Your DC system design will be governed by practical technical considerations in concert with economics. The physics of low-voltage systems are such that they are viable only when current is low; otherwise, a 5V or even 12V system will require prohibitively expensive heavy-gauge wire in order to provide the proper vol…

My budget isn't limited, so that's not a problem. I'm an electrician, so this would be a project for fun. But I know if residential DC became a thing, this would be so easy. I think we'd all be better off with residential DC and solar panels.

Re: Tesla Motors Announces a New Home Battery

#206

Post by SideburnsOfDoom » Tue, Feb 17, 2015, 8:59 PM UTC

brudgers wrote: post #201

SideburnsOfDoom wrote: post #44

Earlier quoted context omitted.

You can get energy out of a lithium battery several times, which puts it well ahead of tearing holes in the earth to mine coal. No, it's not permanently "off the grid" as it depends utterly on the whole industrial infrastructure, but it not continually tied to the grid like a power line running to a coal-fired power station.

TANSTAAFL. You can't get any energy out of a battery until you put energy in ... alas more in than out per the laws of thermodynamics.

yeah no kidding. It would have been a diversion to mention solar; which Musk is also betting on, not co-incidentally.

Solar in similar: it depends utterly on the whole industrial infrastructure, but is not continually tied to the grid like a power line.

Re: Tesla Motors Announces a New Home Battery

#207

Post by IgorPartola » Tue, Feb 17, 2015, 9:06 PM UTC

jacquesm wrote: post #196

IgorPartola wrote: post #183

Earlier quoted context omitted.

This is roughly 2.5 times cheaper than the marine battery I found first, definitely not orders of magnitude. This is $5k for 2 kW * 24 hours. So 3 of these at $15k total would roughly replace my $700 generator + $10 worth of gasoline for emergency situations. To truly run my house where it would be adequate at 20 kW or 24 hours or so, I'd need 10 of these at $50k. To run my house of for a week (where I live, the last…

I think you're more than a bit power hungry. My house consumed max per day, so even running to 50% discharge that bank would power the house for up to 5 days. It's much easier to save on consumption than to create capacity, especially stored capacity. You don't really realize just how much energy goes into AC, heating, washing and so on until you've lived off the grid for a bit. And then you'll quickly learn how to c…

That I suppose is the line for me. I am unwilling to go to a point where I cannot use my washer/dryer, dishwasher, AC, etc. I believe the majority of the developed world is with me on this, though of course there is a minority that have other priorities.

Re: Tesla Motors Announces a New Home Battery

#208

Post by jacquesm » Tue, Feb 17, 2015, 10:11 PM UTC

IgorPartola wrote: post #186

sah88 wrote: post #147

Earlier quoted context omitted.

~30kwh is the national average for daily use. 120 is crazy high unless your blasting an AC or heat all day. At 12 cents a kilowatt hour that's a $438 monthly bill. Even 30 is pretty damn high. For someone living off grid with a purpose built/renovated structure ~5kwh a day gives you quite a lot to work with.

True, but you want to be able to handle peak usage too. When 2 kW well pump kicks in, I don't want the lights to dim. AC is 3-5 kW and more to start, and so on. Yeah, if your goal is to live off the grid to save the planet, that's a different story. Then the only question is how much will your Lithium based battery (mining, manufacturing, transport, recycling) affect the planet vs buying wind power from your local ut…

I did the shorting current calculation on that battery in the pic elsewhere in this thread. The fuse was there for decorative purposes only, at those currents everything is a fuse, the one Ththing you really have to hope for is that it will douse fast enough and that there will be no air/fuel or H2/O2 mixture nearby. That's the main reason I built this pack into a little building (underground bunker really) of its own near the house but not so near that it would be a problem if it would break down.

The inverters were housed in the second half of that bunker so as far as the house was concerned nothing changed.

The whole system was capable of producing 11KW, two tandem 5.5KW inverters ganged to produce 240 V for well pumps and other large consumers (welder, plasmacutter).

It worked super good but you really had to keep an eye on the charge level when running big tools, the plasmacutter would drain the battery in about an hour.

But running the plasmacutter was the exception, not the rule so most of the time it was just powering a very low level of loads compared to most houses.

I really miss the system, and the farm it sat on.

Re: Tesla Motors Announces a New Home Battery

#209

Post by dm2 » Wed, Feb 18, 2015, 4:16 AM UTC

Sir_Substance wrote: post #62

This still doesn't solve the essential problem with these batteries: They're about $20k each, and they only last about 4 years.

The Model S 85kW battery pack is estimated to cost $12,000 and is estimated to last 10+ years.

The SolarCity Battery field-test uses 10kW Tesla batteries and is leased for $1,500 upfront and $15 per month. So, if the batteries degrade, it's Tesla/SolarCities responsibility to fix or replace them.

The Gigafactory will likely reduce costs significantly.

http://www.theverge.com/2015/2/13/8033691/why-teslas-battery...

Essential problem solved?

Re: Tesla Motors Announces a New Home Battery

#210

Post by glabifrons » Wed, Feb 18, 2015, 4:57 AM UTC

msandford wrote: post #122

jacquesm wrote: post #112

Earlier quoted context omitted.

> No matter how well serviced, I've found these batteries don't last beyond four years. Wow, that's really short, especially with such a shallow discharge pattern.

Not necessarily! We don't know how deep the battery is being discharged. But we can make a guess. 4 * 365 = 1400 cycles. http://www.mpoweruk.com/images/dod.gif According to that chart (which is an approximation of course) 1400 cycles corresponds to about a 40% depth of discharge. Which isn't terribly shallow. The other variable is the discharge rate, and the higher it is relative to battery capacity the worse the eff…

I've wondered for years why people always gravitate towards Li-Ion cells when talking about a home storage battery. Li-Ion's advantages are far, far less important for a dwelling. Weight doesn't matter... you won't be moving them. Size doesn't matter nearly as much as it does in a vehicle... losing a few inches off an entire wall in a garage won't really be an issue for most people. Edison cells are incredibly durable and much, much more environmentally friendly than any other battery tech I know of. The lifespan is nothing short of incredible too... you won't need to change them out.

Thank you very much for the 2nd link. I was unaware any company was still manufacturing them. The last time I looked, the last company I could find that made them stopped a few years prior. I'm glad someone is making them still/again and marketing for an appropriate use.

The one odd thing is the price... for something as low-tech (relatively speaking) as an Edison cell, I'd expect them to be much cheaper. Must be the lack of competition.