back to article Tesla's battery put in the shade by current and cheaper kit

A couple more interesting details have emerged about Tesla's “game-changing” home battery, and it remains a moderately limp competitor that's done wonders for market awareness. Courtesy of Bloomberg, the world gets an idea of what the retail from-the-installer price of the battery might look like (rather than the wholesale …

  1. Charles Manning

    It isn't supposed to make sense

    It's just trendy tat to sell to e-hipsters.

    Battery storage is supposed to smooth out the spikes associated with PV and wind, but it is pretty inefficient. New batteries will only give you around 80% efficiency at optimal usage. Worse when the batteries get hot/cold/old or the load is not exectly matched.

    Pump storage has been used for the same purpose for decades, has similar efficiency to new batteries and has a better ROI.

    The scheme I am most familiar with is This has been operating now for 34 years with only relatively minor maintenance and has the added benefit of being able too use surplus electricity to pump water into a different watershed for agricultural use.

    1. Jamie Jones Silver badge

      Re: It isn't supposed to make sense

      Ahhhh, who from Wales could forget school lessons about Dinorwig Pumped Storage Power Station

      1. SolidSquid

        Re: It isn't supposed to make sense

        Don't forget about Cruachan up in Scotland, opened in 1965 and was apparently the world's first reversible pumped storage power stations

      2. Richard_L

        Re: It isn't supposed to make sense

        @ Jamie Jones

        Not just in Wales either, England too!

        I was in a class which had a geography teacher as their form teacher for a few years. Every time it rained and was too wet for us to be turfed out onto the playground for our break, we were sent up to the geography classroom to watch a video. Unfortunately the geography teacher only had two videos. One on Dinorwig, the other on the Milk Marketing Board.

      3. Mike Richards

        Re: It isn't supposed to make sense

        It was on Blue Peter regularly, so those of us East of Offa's Dyke also got to hear about it.

    2. Ilmarinen

      Re: It isn't supposed to make sense

      The problem is though, that this “game-changing” technology was lapped up by the technically illiterate media, instead of being greeted with the laughter which it deserves. This is the same ignorance and foolishness that brings us wind farms, solar arrays (hundreds of acres alone in just my local area) and all the other subsidy scams, robbing the poor to give to the rich and not a jot of "Global Warming" prevented. Wrong, wrong, wrong.

  2. the spectacularly refined chap

    Back of an envelope calculations

    Late last year I replaced the battery in the UPS powering this workstation and I started wondering based on that. I'm not going to go through all the figures but to get to 10kWh using those cells would cost ~$2750 even assuming no bulk discount, and top name (Yuasa) batteries from a proper distributor. They'd have a five year life and 200-300 charge cycles so replace them twice as often and double the comparative price to $5500. Add the circutry needed to generate a mains approximation and we're somewhere in the same ballpark as that Tesla unit. You probably could get cheaper using a more sensibly sized battery to begin with but I'm not going to start optimising there, we'll simply leave this unit and lead acid batteries as being roughly comparable on the metrics used so far.

    OTOH lead acid cells have quite incredibe power density - that single cell in my UPS can deliver 300W. A bank of 120 to store 10kWh would be capable of delivering 36kW on the same basis. Sure, you'd drain it in minutes at that load but if you need the 8kW shower, the 3kW kettle and 2kW oven all on at the same time for a short period the ability is there. And no, all those batteries wouldn't be absolutely huge, again in rough terms roughly a yard square and seven or eight inches deep - call it the size of a radiator.

    This battery seems more of a desperate attempt to find new markets for Tesla's battery tech to cross-subsidise the cars. Sure, it's a nicely packaged solution but it can't cope with real requirements. Proven 1850's tech can for around the same money.

    1. Nick Stallman

      Re: Back of an envelope calculations

      And if you go for some nice deep cycle car or truck batteries instead of the much smaller UPS batteries you absolutely phenomenal capacity.

      A lead acid battery rated at 300 amps (not continuous) equates to 3.6kW for a single battery. And at lower power levels you'd get incredible duration.

      I've got a small car battery dedicated to a 1.5kW inverter for emergencies. A friend had a black out a couple of weeks ago and it kept their TV and Playstation going for about a day before they got power back. The voltage afterwards was still 12.5v which is roughly 50%.

      1. Ole Juul

        Re: Back of an envelope calculations

        "The voltage afterwards was still 12.5v which is roughly 50%."

        My chart shows that 12.5v is 90% and 50% is 12.06v.

      2. Lee D Silver badge

        Re: Back of an envelope calculations

        I was doing the same calculations when the article appeared on Slashdot, and other places.

        Basically, it can't compete with a home-brew lead-acid system using established circuitry, well-known and replaceable battery tech (you could literally buy a new battery a week from the Halfords down the road once they start to run down), and something which people will already have in place if they have any kind of home renewable setup. Hell, I was looking at a 3KW mains inverter from 12/24V and they are in the cheap-commodity price ranges now because of all the solar nuts.

        Just not sure what they think they are selling that's "new". Sure, different battery tech, etc. but it doesn't seem to add anything. If anything, it takes away (look at those charging cycle numbers, and the max surge output power! It's pathetic!).

        I sympathise in that having a company solely reliant on high-end battery technology sucks at the moment. Because we just don't have anything beyond, quite literally, a bunch of laptop battery cells joined together. We just can't compete with that. And the only way forward is to either invent a new battery type that's revolutionary, or make the existing battery types cheaper by producing en-masse. But, sadly, neither option actually solves the problem or gets into the order of magnitude that we actually NEED.

        More worrying, I would think for people who own their cars, is that if the company is really that reliant on batteries, you only need a tiny blip in lithium prices, or for such projects to fail miserably, and all that battery warranty comes to naught and one of the prime components of the cars becomes pretty much unobtainable.

        Sucks to be an early adopter reliant on some magical, mystical technology advances that nobody has.

        1. Bronek Kozicki Silver badge

          Re: Back of an envelope calculations

          You are onto something, but there is a limit of how many lead batteries you can have in a given area, due to their weight. If foundations (and floors) of your home are not designed to take the weight of lead batteries in little space, you will be risking structural integrity of the building by putting too many batteries in one place. In other words, unless the building has been designed specifically for this, you cannot really make much use of this great energy density of lead batteries. Although of course, you can put these to some use and 10kWh does not seem like unreasonable figure - assuming this is not hung on a wall or put in tall tower on the floor with small footprint.

          As for charging cycles, in case of lithium based batteries it actually depends on how much a battery ever gets discharged. If the limit is at 50% (as opposed to standard over 80%) then you can virtually cycle the thing in perpetuity, with only little loss of efficiency (say, 20% as opposed to 50% after 1000 cycles). I do not know how charge cycles are limited in lead batteries though, perhaps someone will enlighten me.

          1. Pallas Athena

            Re: Back of an envelope calculations

            One Powerwall weighs about 100 kg. The solar panels on my roof produce during summer on average 14 kWh a day, with best days bringing in over 22 kWh. Meaning at least 3 Powerwalls of 7.5 kWh, or 300 kg _hanging on the wall_. A house where that kind of weight on a wall is not a problem, will quite likely not risk structural integrity because of a couple of lead batteries reasonably placed on the floor.

            1. Steve Todd

              Re: Back of an envelope calculations

              What kind of house do you live in where 300kg on a wall is a structural integrity issue? On plasterboard partition walls, yes. On structural brick? They can support the roof and upper floors without problems. 300kg, distributed allong a wall, isn't a serious load.

              1. Gene Cash Silver badge

                Re: Back of an envelope calculations

                > What kind of house do you live in where 300kg on a wall is a structural integrity issue?

                At least here in Florida all the houses are matchstick & tarpaper quality. I wouldn't trust 300kg on any wall including an exterior one. Hell, the outside siding is having trouble hanging on after only 10 years.

          2. Ole Juul

            Re: Back of an envelope calculations

            @ Bronek Kozicki "I do not know how charge cycles are limited in lead batteries though, perhaps someone will enlighten me."

            I'm no expert but have been doing a lot of reading lately. It seems that lead acid is the same as your lithium batteries. A 50% discharge will give double the life of an 80% discharge and less discharge even longer life span. Apparently a 50% discharge rate will give the best lifespan vs cost. They say that cycle life varies from 500 to over 1000, but that's for premium batteries. I found a page with a good overview. One takeaway for me was this statement:

            An important fact is that ALL of the batteries commonly used in deep cycle applications are Lead-Acid.

          3. Mage Silver badge

            Re: Back of an envelope calculations: Perpetuity

            "then you can virtually cycle the thing in perpetuity"

            No, you can't.

            Lithium cells store best at about 66% charge.

            They start degrading with time as soon as made even if not discharged. For off grid you need to store daylight energy for night time. So cycling is daily and perhaps 1/3rd discharge for new batteries and after a year or two that might be 50% of capacity as capacity reduces with use (and time for Lithium Ion).

            I recently charged a New Old Stock 40 year old Lead Acid cell. It's fine because it was never filled with acid. Sadly today shops store Lead Acid batteries pre-filled, so check the date code!

            There are really two main kinds of Lead Acid Gel cells. The UPS/ Alarm / Emergency light float applications and the regular cycling (portable lamps and inverters) were it's discharged daily.

            They are more for standby or portable use at lower AH than 40AH

            Gel types are poor at high pulse currents compared to wet,

            There are several flavours of wet lead acid:

            General Purpose

            High pulse current (for starter motors). These don't like deep cycle. Typically 30AH to 200AH and 12V.

            Industrial UPS standby. There may be a generator too. Much higher power than single PC / Server UPS.

            Regular deep cycle (i.e. night time on off grid solar). Typically sold as 2V 200AH or larger capacity.

            Only units subject to movement / vibration need fibreglass mat spacers.

            They have different plate constructions. Life is shorter on all types if the battery is completely discharged. But this is perhaps more true of Lithium Ion. The NiMH in contrast can be stored discharged (better actually!) and don't have a problem with full discharge.

            All types technology reduce in capacity with number of cycles, so for off grid night time use double the kWH capacity needed.

    2. ARGO

      Re: Back of an envelope calculations

      "Add the circutry needed to generate a mains approximation"

      That's already present in a solar inverter, so with a bit of system level design you wouldn't need to provide it in the battery pack.

    3. Steve Todd

      Re: Back of an envelope calculations

      There are a number of good reasons why you"d not want to use lead acid (beyond just the weight).

      Firstly, if you want to get more than a few hundred cycles out of them you need to limit yourself to not more than 50% discharge (30% if you want 10 years life out of them).

      Secondly you lose power during charging lead acid (ignoring the losses in the charger circuitry) to the tune of about 15%

      Thirdly you need a three stage charging circuit, and for the top 20% you need to trickle charge otherwise you knacker your battery life (as does NOT giving it a 100% charge).

      The cost of a lead acid system may be lower in the short term, but it's more over the 10+ year lifespan we're talking about and produces some fairly noxious ewaste into the bargain.

      1. Mage Silver badge

        Re: Waste

        produces some fairly noxious ewaste into the bargain.

        Lithium Ion recycling, Oddly not Lead Acid, Most Lead Acid Batteries in Europe are easily recycled as new Lead Acid Batteries. The Lead can be essentially reused easily forever. Lithium batteries are far more energy intensive to recycle and don't last as long.

      2. Bob H

        Re: Back of an envelope calculations

        I can't find the site, but this week I read a fantastic analysis of the Tesla solution which included life, cost and carbon impact. It compared existing battery techniques vs some other solutions. The most notable thing was that they said the cycling of Lead Acid vs Lithium effectively gave you double the life. The carbon impact was less but it wasn't ground breaking. The basic thing is that Lithium batteries can be cycled more deeply than Lead Acid, that depth of charge means you need fewer of them for a given demand, because of the better cycling performance you can also make them last longer. So, Lithium ion gives you twice the life, a fair bit more expensive, but a good carbon footprint.

        I further did my research and found I could build the Tesla system for the same or less. I might build it because I have an off-grid project, but it isn't a trivial build.

  3. Ole Juul


    Existing sellers are probably going to get a boost from this. In fact I wouldn't be surprised if Tesla sells more of other companies batteries than their own with this campaign.

  4. bazza Silver badge


    Using expensive, fiddly, light weight lithium batteries in an application like this where weight just isn't an issue is nuts. It's the kind of thing you sell if you can get away with it, or if you have got too many lithium cells not being used in your original market.

    Using cheap, simple, any size you like, well understood, easily serviced, easily charged and recyclable lead acids makes much more sense.

    1. Matthew 17

      Re: Crazy

      You have the issue of physical size and life with Lead batteries.

      The marketing angle for this is that you could have one at home and mount it on a wall. With Lead it would be at least 3 times the size.

  5. Benjol

    "Germany, where the economics of solar power are well-understood"

    That is: expensive, and backed-up by smog-belching coal power stations?

    1. AlbertH

      No - it's backed up by cheap, clean nuclear and hydro-electric power from France!

      1. Chemist

        Suggest you read :

        Page 6 ;- first 11 months of 2014 total generated electricity ~470 TWh

        46% coal, 9% wind, 7% solar,

        1. Code For Broke

          And the other 38% comes from... (wondering if the burning of Greek bonds fits in here somewhere)

          1. Chemist

            "And the other 38% comes from"

            Well if you can't be a***d to read the ref !

            Nuclear, gas, biomass, hydro. ( I've got a German neighbour here in Switzerland and he often spouts off about how much cleaner German electricity production is " Mostly wind and solar" )

            Greek bonds might well be biomass

        2. Crazy Operations Guy Silver badge

          Coal power and Radiation

          I think find it hilarious (In the German meaning) that coal power plants emit magnitudes more radiation into the atmosphere than nuke plants...

          It makes me so angry that some corrupt energy execs in Japan running crappy Gen II plants built in the 60's have ruined nuclear energy for everyone. Especially since those plants would have been safe if they even did something as minor moving the generators to the top of the hill, built up the seawall to match the plant further up the coast, or even just had a couple of truck-mounted generators stored in a safe place that could've been brought in. None of these would have cost all that much, probably about $1.5-2 million for the whole complex of four reactors, but they didn't want to spend it so the whole world is doomed to use fossil fuels to generate the bulk of our electricity...

      2. Charles Manning

        Nuke in Germany? Certainly not!

        They filter out all the nuke derived electrons at the border so that the volk only have untainted leccy.

        This is done with a filter made from crystals ground up and suspended in pure mineral water. The nuke electrons have a different vibration and bounce off the crystal particles and go back to France.

        This is the same technology Apple uses to ensure that they only use untainted sustainable leccy from the CA grid.

    2. TeeCee Gold badge

      Well, that's what you get for having a wobbly coalition government. Decomming all the nuke plants to keep the leaf-munching luddites on message[1].

      Looks like we might be about to get a taste of this arsehattery.

      [1] A very strange leaf-munching luddite requirement that involves choosing lignite (brown coal - dirty as it gets) as your power source of choice. Makes you wonder which foot the German greens are going to shoot off next time they get their sticky paws on the levers of power.

      1. theModge

        leaf-munching luddites

        ....which is exactly why I couldn't bring my self to vote for our own leaf-munching luddites.

        Voting today really did make me feel dirty, but it has to be done.

  6. Pallas Athena

    50 load cycles a year??? Forget about price, forget about the 2kW max output. If this battery is supposed to store solar-energy during the day, and provide off-the-grid power at night (that's the way it was announced), then 365 load cycles a year would be required. Even an on-the-grid scenario where you only want to smooth out the peaks, in a location with lots of dark winter days, easily could require 200 load cycles a year - meaning you'd have to buy four times the capacity!

    1. Anonymous Coward
      Anonymous Coward

      The bloomberg article states clearly that the intended use of the 10kWh is as a backup and not for daily use, hence the comparison with the generator. The 7kWh battery is the one designed for daily use...but it's not available yet since it currently doesn't make financial

    2. redav

      There are two versions. One is described as offering a daily-load cycle. The other is described as being for a weekly load cycle. It's scarcely cutting edge journalism to suddenly discover that the weekly load cycle one only supports about 50 load cycles a year, is it?

    3. Charles Manning

      50 load cycles a year

      Sounds like the key customers are in Blighty.

  7. This post has been deleted by its author

    1. FuzzyTheBear

      Re: 16kW generator for $3699?

      Indeed , a decent gen set , the transfer panel , emergency panel , installation ( muffler , gas / diesel tank / natural gas/propane tank + electrical work ) , decent vibration damping and possibly a remote emergency panel will cost a heck of a lot more than 3699 $

  8. BobRocket

    Max Power

    The 2kW max load is not a problem if all of your domestic devices added together draw less than that.

    (this is from the mirror so I won't include the link)

    'The average power of a vacuum cleaner on sale in Europe is 1,800 watts. This will have to be halved within the next three years, as the limit of 1,600 watts will be reduced to just 900 watts from September 2017'

    Hoovers will still suck.

    Restricting the maximum load of a device will force designers to improve efficiency (at least at the enduser point).

    Restricting the amount of fuel you can buy for a pound (by punitive taxation) has lead to the increase in mpg of vehicles.

    My kettle is rated as 2.5kW, it boils a cup of water reasonably quickly but watch what happens when you turn it on, hot bubbles form around the element, detach and rise to the surface releasing some of their heat on the way up but most of the heat is given up to the atmosphere.

    Any water left in the kettle cools quickly due to lack of insulation.

    It can't be beyond science to have a 1.25kW kettle boil the same amount of water in a similar timeframe, if you restrict kettle elements then someone will find a way (and make some money in the process)

    Neccesity (natural or artificial) is the mother of invention.

    1. Spoobistle

      Re: Kettles

      "My kettle is rated as 2.5kW, it boils a cup of water reasonably quickly but watch what happens when you turn it on, hot bubbles form around the element, detach and rise to the surface releasing some of their heat on the way up but most of the heat is given up to the atmosphere."

      Most of that is dissolved air coming out of solution, and nothing to do with the heating.

      "Any water left in the kettle cools quickly due to lack of insulation.

      It can't be beyond science to have a 1.25kW kettle boil the same amount of water in a similar timeframe"

      As James Joule convinced us many years ago, it takes a fixed amount of *energy* to raise the temperature of water to boiling, so twice the *power* takes half as long - assuming a perfectly insulated kettle, and that's the real point. A crappy uninsulated 1.25kW kettle will be no better than a crappy uninsulated 2.5kW kettle and probably worse because more heat is lost in the longer time to boiling. If you want rules about kettles, make them apply to the insulation, not the heating power.

      1. Boothy
        Black Helicopters

        Re: Kettles

        Instead of restricting power to a specific input amount, would not a more sensible approach be to rate devices on the usable power, i.e their efficiency?

        e.g. for a kettle, how much of the energy into the device, goes into the water, and is still there once the heating cycle competes? (i.e. Takes into account losses due to poor insulation).

        Then set a minimum efficiency threshold. Say 75% to start with, then later 85%, then a few years later again 95%

        That way people could still have their 2.5KW kettles, but their increased power simply boil the water faster, but with no more wastage than a same efficiency rated 1.25KW kettle.

        I suspect the primary aim here by 'them upstairs' is not actually an increase in efficiency, they just want to reduce the peak load times when the advertising breaks kick in on the TV and everyone goes to make a tea/coffee.

        1. theModge

          Re: Kettles

          ...actually, I assume it's because in Brussels they don't fully understand the importance of a decent cup of tea. It's coffee or nothing there, if you are English.

          (and no, I did not vote kipper)

        2. Anonymous Coward
          Anonymous Coward

          Re: Kettles

          I think you tend to hit a ceiling with efficiency. Physics dictates you can only transfer energy with so much efficiency given the properties of the materials used in the construction of the heat source and container. Trying to improve these probably falls into the realm of diminishing returns due to the need for ever more exotic materials for the heat transfer plus potential reduced safety. I mean, a metal kettle will conduct heat throughout its metallic body, and at least some of this heat will be lost to the outside air through convection and radiation (thus why the sides of the kettle tend to still be too hot to touch even if not directly exposed to the heat).

    2. JP19

      Re: Max Power

      Technically illiterate moron - just the kind of customer Tesla needs.

      1. BobRocket

        Re: Max Power


        Whilst I may currently be a 'Technically illiterate moron', with a bit of education I could become literate, you sir however would still be an arsehole.

      2. gptgpt

        Re: Max Power

        Damn the laws of thermodynamics, all we need is the to invent insulated water. Or....all we need are more restrictive laws and to increase the amount of government meddling in the world and Utopia can be ours!

    3. BobRocket

      Re: Max Power and kettles

      1. The bubbles are comprised of mainly air coming out of solution, these form around the element first and so are heated most and being less dense than the water surrounding them rise to the surface and escape into the atmosphere taking some of the heat with them.

      2. In a fully insulated container a heating element of twice the power will boil the water in half the time (all other things being equal). I could boil the same amount of water in one tenth of the time by using a 25kW kettle.

      Great except it would have lost a lot of its heat by the time I have located and rinsed a mug, put in sugar and teabag etc. It seems a 2 to 3 kW uninsulated plastic jug kettle boils water in the right timeframe.

      I could change the order of the process but people have been doing it this way for years hence the phrase 'i'll put the kettle on' rather than 'I'll find some cups'.

      I could use a lower power element in the current design but it would take too long to boil so if I can't increase the load (due to an external constraint) I will have to redesign the kettle.

      3. As the OP points out it is a loading issue. (we're talking 2kW load here)

      At the moment there is sufficient extra capacity in generation to let me use any amount of domestic power I like (subject to wiring/fuse constraints), this spare capacity that might never be used costs everybody to keep available.

      If it wasn't available then I would soon learn to live within the limitation or provide my own when I want it.

      If I never need it then why should I pay for all this infrastructure just in case you do ?

    4. Fuzz

      Re: Max Power

      There is a way to make kettles more efficient but it's not reducing the power. The trick is to make the kettle only heat the water that you need rather than the amount you pour in.

  9. Andrew Jones 2

    Did these people not even bother to read the press kit? The 10kW battery is designed for BACKUP ONLY and specifically says that it is optimised for WEEKLY charging - the 7.5kW battery is designed for DAILY charging. The comparison to the generator is laughable - because it's running off fuel - why even bother - that's like saying Solar panels are prohibitively expensive and it would be cheaper to run from a generator - well guess what - it would be even cheaper just not to bother with renewable energy at all and just take your electricity from the grid.....

  10. Archivist

    Load balancing

    I have a 10MWh battery store near my house:

    Apparently these batteries use Lithium chemistry but their construction and weight makes them unsuitable for portable applications.

    1. JP19

      Re: Load balancing

      "I have a 10MWh battery store near my house:"

      "The project was awarded £13.2m from Ofgem’s Low Carbon Networks Fund"

      At least 75% paid for by tax payers because it makes no economic sense.

      1. Anonymous Coward
        Anonymous Coward

        Re: Load balancing

        See also a separate project at:


        Another justification I have seen for these is entirely independent of the renewable energy storage aspect.

        A few MW (a few MWh) of 11kV-connected storage may allow a distribution network operator to avoid upgrading their distribution infrastucture.

        Can't comment on the commercial validity but technically it sounds vaguely plausible. You've got X MW supplies into a district whose peak demand 3 years from now will be X+15%, and which from time to time already hits X+2%. Put in a grid-connected battery of X/10MW and you've avoided (for now) upgrading the supply to the area?

        That was the premise quoted, anyway.

  11. breakfast

    How does it stack up to current batteries?

    I was staying at a friend's place somewhat out the way in Australia a while ago, where mains utilities aren't a thing, so they get all their electricity from the sun and store it in what looked to me like a bigger version of regular leisure batteries. That provided enough electricity to keep everything running in the house well enough.

    Are there any reliable comparisons around of how the Tesla specs match up to the solutions currently used in that type of environment?

  12. Anonymous Coward
    Anonymous Coward

    Details, details

    This is an interesting development for us, as we're off grid. The idea seems sound to me, to have an all-in-one device that contains the circuitry to charge, invert, feed-in and feed-out. That's the interesting bit, not the battery bank or capacity.

    FWIW, we have a 15kWhr bank, never taken below 50% SOC, as that kills the life. But we don't think of its capacity in kWHrs, as that's useless. Amp-hour rating is more important. Comments here about batteries with 300A capability are not too relevant, as these are for car starting conditions, not the typical requirements of deep cycling. And assuming you /get/ the full rating from a battery bank is also misleading, though admittedly non-lead-acid batteries are less affected by deep discharging.

    We installed a desulphation unit, a simple device that puts a high frequency pulse across the terminals constantly, and that has keep the batteries sulphation-free for 6 years (touches wood.) Sulphation and over-deep discharge are the two killers of lead-acid batteries.

    But our conditions, off-grid, are not really anything like those for which one assumes these Tesla power packs are designed. Our details just for interest...

    1. Badvok

      Re: Details, details

      "But we don't think of its capacity in kWHrs, as that's useless. Amp-hour rating is more important."

      Yes, of course it is totally useless thinking about the actual amount of energy available rather than just the number of Amps :rolleyes: I suggest you go back to school, you need Amps and Volts together, one without the other is meaningless. Watt do you get from Amps and Volts? (clue in question.)

      1. Anonymous Coward
        Anonymous Coward

        Re: Details, details

        Gosh, a simple bit of information on real world experience shouldn't elicit such a response. But still, let me try to be a little clearer. If you are off-grid, then you have to take steps to ensure you do not over-tax any piece of the system, and one of those is the battery bank, which, if you abuse it, reduces the life of the most expensive component dramatically. Power comes in from wind and sun, and that you can see using an ammeter. Rough state of charge is given by the under-load voltage. We know we can use around 300 AHrs of a fully charged battery bank assuming no charging regime, before we start damaging the battery.

        Now there is no point in doing the maths to tell us power input and output in kilowatt hours, as we have to concentrate on the two things easily measured. Yes, after 7 years of off-grid living, I do know one or two of the more basic formulae, but I was simply commenting on how things work in practice. I hope that makes things clearer.

        If I'm missing some practical knowledge about managing a battery bank using kilowatt hours, I would very much like to know more, though, but if it's just ideal bench theory, well, that's a bit less helpful.

        1. Badvok

          Re: Details, details

          "We know we can use around 300 AHrs of a fully charged battery bank"

          Is that a 72kWh battery bank able to supply those 300 Amps for an hour at 240V, or a 0.3kWh battery bank able to supply those 300 Amps for an hour at 1V? I think there might be a slight difference in size and cost between the two but they are both 300 Ah battery banks.

    2. MachDiamond Silver badge

      Re: Details, details

      I didn't see a manual on Tesla's web site, but the Powerwall packs might only be usable in a grid-tied system from how there marketing fluff reads. The tiny amount of information available isn't enough to make an informed buying decision. I read another article that stated the Powerwall didn't come with an inverter. At this point, they are vaporware.

      The best backup battery is likely to come as a kit for a used car pack that doesn't provide enough range anymore, but is perfectly serviceable for a home application. DIYr's are snapping up the used Prius NiMh packs since they are easy to refurbish and not as fussy as Li chemistry batteries.

      Somehow I think that P.T. Musk is trying to forestall competition before the Gigglefactory is producing.

      1. old man

        Re: Details, details

        Hi interesting article and comments by lots of folk but that part you mentioned about no manual I enlarged one of the photos of musk battery packs .There is no control gear or inverter gear you only get the battery for that price, better look up Halfords for lead acid batteries .

  13. Alan Denman

    Get a life times 4

    Why buy this rubbish for home use when you can buy LifeP04 for close to the same price ?

    Yes, it kickstarts the market but it is a pretty crap offering. Tesla lasts 10 years 'if you don't use it' whilst LifeP04 in the same rubbish scenario lasts 40 years !

    The standard Lithium is built for lightness but until the hype was not really deemed sensible for home use.

    1. OldTimer1955

      Re: Get a life times 4

      Ah, yes - the Lithium Iron battery.

      iirc that is what is/was used to provide backup power in submarines. Long life, high cycle capacity and reluctance to burst into flames.

      Seems ideal for off-grid storage, so why is it not more popular?

      1. raving angry loony

        Re: Get a life times 4

        Why not more popular?

        - cost

        - life cycle

        - total lifetime

        - total cost of ownership

        Off-grid living and military vehicles (including submarines) have totally different requirement documents.

  14. Pete 2

    Double or quit

    And if you really are off-grid and rely on this technology to keep you powered up, you'll need a backup in case of failure (guarantees are nice, but they don't keep the lights on and if it takes a week to deliver a replacement to your remote, off-grid location ... ), or for those times when your "old" battery is being replaced.

    The thing about multiple LA batteries is just that: you already have the makings of a resilient solution. Or at least one that can operate at reduced levels, rather than being a single all-or-nothing proposition.

    So, as with all H.A. systems: computer or home, the cost of a truly reliable system is a multiple of the cost of a single purchase.

  15. Mage Silver badge

    Lithium Ion

    The tech makes sense for reduced weight. Such as cars, phones, laptops.

    In terms of volume, not weight, the NiMH is close and can do more full cycles. My laptop is on it's 5th 14.8 V 5.2 AH pack, and is mostly used on mains, not off grid.

    How much capacity does the 7KWH battery have after 700 cycles of 50% discharge (i.e. Off grid and using electricity every night, the sun don't shine)?

    Weight or space isn't an issue for fixed solar applications, mobile mast or telephone exchange backup. Hence they use Lead Acid.

    In Europe almost all the lead in Lead Acid batteries is recycled to make Lead Acid Batteries. The manufacturing cost and energy input to make Lead Acid batteries is far lower than the same capacity of NiMH or Lithium Ion. They are simple, and also with recycling much "greener".

    1. Anonymous Coward
      Anonymous Coward

      Re: Lithium Ion

      "In terms of volume, not weight, the NiMH is close and can do more full cycles"

      I like NiMH technology - it's actually a rechargeable hydrogen cycle with the hydrogen stored in mischmetall, very neat technically - but it uses an awful lot of nickel and cerium, which are not cheap and have lots of other uses. It's better to concentrate on lithium and aluminium technologies from the point of view of resource constraints - at least for the next 10 years.

    2. Alistair Silver badge

      Re: Lithium Ion

      I can see you've never been anywhere near a lead acid battery recycling plant.

      Sadly, at least over here, there are no requirements to filter the air coming out of the plant. And I know a fellow that worked in one. And the kit they wore in there, the rules about tears in the suits made it pretty clear how "green" that air was.

      I'll admit, at least they *are* recycling the stuff, and it makes it cheaper, but the acid is neutralized and tossed down the pipes around here. The dust from the grind/melt process and the off gasses from the "smelt out the plastic" routines are pretty damned nasty. The smelter output is run through filters, but the grinder room is open to the environment.

      1. Mage Silver badge

        Re: Lithium Ion

        Have you seen a Lithium Battery recycling plant for the same KWH per month of battery recycling?

        The cases could be reusable on Lead Acid. There is little room to improve Lithium battery recycling.

  16. Richard_L

    Not to defend Tesla in particular but rather to question people's expectations... I think that people have to stop branding the Powerwall battery a failure because it can't power all of a household's high wattage appliances at the same time.

    If you're already off-grid, then you're probably already well aware that electricity usage has to be somewhat planned and you can't just wake up in the morning and fire up the toaster, kettle, oven, electric shower, hairdryer, curlers, washing machine and dishwasher simultaneously and to suggest that this battery, which is probably smaller and less robust than a lot of true off-grid'ers battery banks, should be able to do that seems rather unfair.

    It's most valuable achievement seems to be raising awareness of the need for energy storage in a green energy dominated grid. Whether it's a good product seems rather less certain from the specs. I thought lithium cells were supposed to avoid the lead acid pitfalls of limited charge cycles and death by excessive discharge etc? Apparently not these...

    Perhaps a more natural market for these sorts of mass-market, plug-and-play, all-in-one, certified and standardised solutions will develop as an integral part of a smart grid, controlled by the National Grid who would govern when and what wattage the Powerwalls would release to homeowners:- With the Grid sending out automated messages like "Calling all Powerwalls... calling all Powerwalls... calling all Powerwalls: The Greens haven't touched their lentil and bean soup today and so mighty fleets of wind turbines aren't quite spinning fast enough to generate enough electricity to meet demand. Can you all switch on and each reduce your house's draw from the grid by 500W using the energy you were able to store from your solar panels earlier when the sun was still shining out of the Greens' arses"

  17. Anonymous Coward
    Anonymous Coward

    The P.T. Barnum of the 21st century

    Musk could sell sand to some of the braindead Arabs. Even though his EVs and Powerbricks make no technical sense, some braindead people will buy them. That's easy money for Musk to extract so he'll continue to dupe the gullible.

    Anyone with a clue can understand the false premise under which EVs and Powerbricks are being sold. But hey there is a sucker or two born every second so Musk should have no problem making a fortune.

  18. bjr

    Lead is cheap, Lithium isn't

    There is a reason that UPSes mostly use old fashion lead acid batteries instead of lithium, lead is cheap, very very cheap. In fact lead is the very definition of a base metal. Lithium is favored in mobile applications because it's light, that matters to the phone in your pocket and it really matters in a car because the energy used to move a car is directly proportional to the mass of the car, for those of you who didn't take freshman physics the equation is

    K = 1/2 * M * V^2, i.e.

    Kinetic Energy = 1/2 * Mass * Velocity * Velocity.

    So if you cut the weight of a moving vehicle by 50% you cut the energy used to get it to speed by 50%. However a battery pack that sits in your basement has a velocity of 0 so the weight doesn't matter as long as it doesn't exceed the load limit of the floor which in the case of a typical concrete basement floor is very very high. So the only factor that matters for a backup battery system is lifetime cost and that's an area where lead acid batteries are always going to beat lithium batteries because no metal is cheaper than lead, and the process for making a lead acid battery is dead simple. Also lead is really easy to recycle when it comes time to replace the batteries because it's melting point is so low as anyone who has ever soldered a wire or a pipe (before they banned lead solder) knows.

  19. David Kelly 2

    2kW Clothes Iron?

    “The model puts out just 2 kilowatts of continuous power, which could be pretty much maxed out by a single vacuum cleaner, hair drier, microwave oven or a clothes iron.”

    Such is the sorry state of science & mathematics in journalism these days that the above fool sentence was published. At least in the USA none of the above is used on larger than a 120V 15A circuit which is rated for 12A continuos duty (1440 Watts). Admit one can not run much more but to imply "maxed out" one is suggesting one is at or over the limits, not 72%.

    1. John H Woods

      Re: 2kW Clothes Iron?

      "Such is the sorry state of science & mathematics in journalism these days that the above fool sentence was published. At least in the USA ..."

      We don't all live in the USA. There are several devices in my house in the 2-3kW range that plug into the conventional circuit. (Furthermore our socket circuits are usually ring circuits rated at 30A).

  20. Anonymous Coward
    Anonymous Coward

    Kettle efficiency

    Funny you should mention this as I have been on a Kettle Effiiciency program lately, after one of the kids (the one with an unfortunate congenital condition that makes a propeller stick out of the top of his head), asked about it.

    Phase 1) The new kettle is glass see through with graduations on the side. I have gotten into the habit of working out exactly how much water I am going to use , and filling exactly. Added a few extra special marks like 1,2,3 tea mugs.

    Phase 2) I now fill it from the hot tap whenever I can. **WTF???** you ask. Well changed the water system to solar. I might hook the electric element in the cylinder up, when the missus complains about getting a cold shower. Here we are one month from the winter solstice, and it still hasn't happened.

    Phase 3) The kids came back from the op-shop with a big thermos. Now I am using 1 thermos as a tea pot, and another for boiling water when I make too much.

    The nett result was 80% drop in power used by the kettle. Most of the energy went on boiling the same water again and again, and making endless cups of tea that get 50% drunk, then go cold. Saved a fair bit on tea as well. And mostly I have instant tea (properly drawn) and instant hot water - don't have to wait for the kettle.

    1. Lee D Silver badge

      Re: Kettle efficiency

      The problem I have with such efficiency drives:

      Multiply by time. The kettle might be stupendously powerful. But unless it's on for an hour at a time, it's not really worth counting. The more powerful kettles boil even quicker.

      All your faffing about, if it boils ten litres a day, might say you a single unit of electricity. Maybe.

      Sure, it's a lot of energy, but it's not the end of the world.

      However, as pointed out, a quite jaunt in the shower might - on electric - be as powerful (or more) and last 15-20 minutes, for multiple people, multiple times a day. That's a lot more power.

      All the messing about buying glass kettles and thermos and transferring from one to the other and taking only a little bit of water and so on and so forth... I can't justify the hassle.

      And what you want could have been achieved easier with those taps that boil the water for you on demand, the same as the heating elements in the cheap coffee machines that can produce instant boiling water. Nothing is "kept warm". Nothing is heated unless it's to boiling point. And you heat only as much as you need to boiling point.

      Two approaches, same cost-saving, one a luxury and convenient, the other messing about with thermoses and drawing lines on your kettle and educating your kids. And, actually, the one with the much higher temporary draw on the power supply, seems to make much more sense to me when you figure out the energy made to produce a glass kettle or vacuum-sealed glass thermos.

    2. old man

      Re: Kettle efficiency

      Hi not that I want to rain on anyone parade but don't ever drink water from a hot water storage tank . The water temperature is usually just perfect for legionnaires and other bugs to grow. Boiling the water will indeed kill them ,but that is boiling the water for 10 minutes not just for tea . While your immune system is good it wouldn't be so much of a problem but if you any other infections it's a different story.

  21. raving angry loony

    Marketing over facts

    It's just another example of how good marketing makes up for massive technical faults in a product. We see this everywhere around us. It's not those with the best technical solution that win, it's those with the best marketing lies and press coverage.

  22. Brian 3

    Am I the only one who has wondered if these things aren't hugely overprovisioned with cells so that a "full discharge" is in fact, more like a 70% discharge?

  23. dave 93

    Missed the point

    It isn't about the minutiae of which battery from which supplier.

    The interesting part is that Elon Musk, a proven tech innovator, has pointed out that renewable generation + battery storage is actually viable, and do-able.

    Like him or not, people do listen to him - and like them or not, PayPal, Tesla and Space X have real working products.

    The Tesla Power Wall will be a working, consumer grade product that people will buy, partly because of belief in Musk's vision (which is an altogether positive vision for CO2 reduction).

    Tesla have open-sourced all the technology for others to build compatible products.

    Credit where credit is due, and a big fat battery for fast charging in every garage would help kickstart the switch to electric transport too. Surprise, surprise!

  24. dave 93

    Just the right shape

    To go on the roofrack of an electric car!

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