Redflow Exec: Our Home Battery Storage Product Is Better Than Tesla’s

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Originally published on RenewEconomy.

Simon Hackett, the executive chairman of Australian battery storage developer Redflow, declares himself to be the number one fan of Tesla electric vehicles in Australia. But he insists that Redflow’s battery storage product is better than the Tesla Powerwall.

redflow-launch-590x371Redflow threw down the gauntlet to its much-hyped international rival on Wednesday, announcing the release of the ZCell battery storage product, bigger and more expensive than Tesla and other big name products, but one Hackett expects to be a force in the market.

“As Tesla’s biggest fan in Australia I’ve got a view that they’ve got the best battery technology for cars, but we do a better technology for houses and that’s totally cool,” says Hackett, who has bought Tesla Roadsters and several Model S electric vehicles, has orders in for the Model X and will also be head of the queue for the new “mass market” Model 3.

“I expect Tesla to sell a hell of a lot of Powerwalls and the nice thing is that we have a market here that is going to explode, it’s not a matter of them having to lose for us to win or vice versa and you can appreciate as well we make a battery that’s a lot more grunt, a lot more capacity,” Hackett told RenewEconomy in an interview.

Hackett expects the market for battery storage in Australia to be “huge”. This, he says, will be driven by Australia’s high grid prices, its big rates of rooftop solar installation, a desire for more grid “independence”, and a wish to do something for the environment.

“I’m seeing the same set of signals from human beings that I saw at the start of the internet boom,” says Hackett, who made his fortune with his company.

“The batteries have gone from something that people that use to talk about in dark corridors to something that is a dinner table conversation in  households.

“Tesla are the catalyst here, not the cause. The cause is that the conditions are right, batteries are … starting to approach the cost where we can have these conversations.

“It’s a tipping point in my view , you can see it a year ago you couldn’t have this discussion with a random person about batteries, now every second person I talk to engages me about it.”

Redflow on Wednesday announced pricing details and specifications for its households battery storage system that it has dubbed the ZCell. The 10kWh battery storage system will be installed for between $A17,500 and $A19,500 a system. Redflow says that is competitive, on delivered energy and capacity, than its rivals.

On a back of an envelope calculation, if a household had the product for 10 years, and discharged it fully once a day, that translates into delivered cost of energy in the mid 40c/kWh. A lot for most households – although some, including low energy users, are being hit for that much because of high grid costs.

Hackett says initially the battery storage costs doesn’t matter so much. The market will be driven at this stage by early adopters, people who simply want to be part of it. Then, as costs come down, and they surely will – just like solar in the past decade – it will become a mass market product.

Hackett says the driver for battery storage is the same that inspired people to buy the Prius hybrid vehicle.

“There’s an inclusion point where people felt like they wanted to buy a car that was more part of the solution, and not part of the problem,” Hackett said.

“If you feel that the world is heading to a bad place in various ways, global warming etc, a battery in your house in the future won’t fix it. But for a lot of people I think its makes them feel that they’re becoming apart of the solution rather than continuing to contribute to the problem.

“If you’ve got a power station on your roof that you can keep energy in one of our batteries and you can charge your EV when you come home, now you’ve genuinely done something . You’ve actually created solar power transport.

“The combination of a solar battery on your house and mobile battery in your car lets humans make their transport fuel on their roof. Now that’s actually new.”

Hackett is not a supporter of the idea of going off-grid, although he admits people will do that because then can, and some will want to. For most, however, the grid will act as the cheapest form of back-up. It’s just a question of pricing that service.

“The question to ask is generally how often are people prepared to be without power, and often the answer is “I’m prepared to be without power”. If you’re in a metropolitan area and you don’t want to be the only house without power, then you need to stay on the grid or have some kind of back up generator.

“I think were getting into an era where there are pretty cool back up generators are turning up, like gas fuel cells. But the point is that you need to be budgeting for that if you want uninterrupted power, or you need to treat the grid like a leased gen-set.

“I agree that the grid operators don’t need to price themselves out of existence, but my strong view is that 5 years from now the smart ones will have realised they want battery storage operated to send power back when the grid needs it.

“We just have to get through this valley in the middle where the perception is that they’re anti battery.”

Hackett, however, describes the idea of “vehicle-to-grid” – using EVs to power up the house as a “bit of a furphy”.

That’s because he believes that the cost of battery storage will fall to such an extent that it will no longer be a question of having battery A or Battery B, but having both.

So why buy a flow battery?

Hackett says: It’s bigger, it’s better suited to a heavy workload than lithium-ion batteries, it doesn’t need active cooling, and it’s local. “It’s designed in Australia for Australian conditions,” he says.

Reprinted with permission.

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is the founding editor of, an Australian-based website that provides news and analysis on cleantech, carbon, and climate issues. Giles is based in Sydney and is watching the (slow, but quickening) transformation of Australia's energy grid with great interest.

Giles Parkinson has 596 posts and counting. See all posts by Giles Parkinson

77 thoughts on “Redflow Exec: Our Home Battery Storage Product Is Better Than Tesla’s

  • Unfortunately it is about 75% efficient round trip. So at 100% depth of discharge that is 7.5 kwh. The warranty is for 10 years, but the fine print says 30,000 kwh. That is 3000 cycles, not 3650 cycles which is one full cycle per day for 10 years. The price is about $18,000 Aus. At todays exchange rate $13,810 USD.
    Cost per kwh at warranty figures 30,000kwh x .75% efficiency = 22,500 kwh.
    $13,810 divided by 22,500 = 61 cents kwh.
    Well….nice try.

    • I’m not sure but i think that round trip is input efficiency multiplied by output efficiency.
      Input efficiency doesn’t count into the total effective storage .

      So, if the battery has 86% efficiency on input and 0,86% on discharge, really has 8.6kwh real retrievable amount of energy.

      • Why doesn’t input efficiency count?

        • This is not a lithium battery. the available and accessible capacity is 10kWh’s.

          The efficiency is determined on the power charge /discharge side (round trip efficiency).

          Efficiency and capacity is accounted for in the power and energy ratings.

          All batteries including lithium have inefficiencies (power in power out). what is of a greater concern is degradation.

          part of the power losses come from power electronics. take that out of the mix and there isn’t much difference.

        • Because 10kwh is the amount of energy that you could put into the battery.
          You can send 10/0.86 ~=11,63 kwh to the battery that 86 input efficiency and you can store 10 kwh.
          Later you extract 8.6kwh so total efficiency is aprox the 75% of the roundtrip, but the battery can store the 10kwh that, with the discount of discharge efficiency, makes 8.6kwh real usable storaged energy.

          • Oscar, in Australia if a battery is sold as a 10 kilowatt-hour battery it has to be able to output 10 kilowatt-hours, otherwise the people selling it are doing what is know as lying.

          • I think Oscar was simply pointing out that even if 10 kW⋅h was the “internal” battery capacity, the user-visible part would still be much higher than what @vensonata claimed.

            I agree that it should represent what the battery system can actually put out, at least when new (and that’s probably why Tesla now specify 6.4 kW⋅h, not 7).

          • What is a 10 kwhr battery with 92% efficiency then?

          • Eveee, it’s a 10 kilowatt-hour battery with 92% efficiency. If you can only get 9.2 kilowatt-hours out of it then it is a 9.2 kilowatt-hour battery. The battery capacity is measured by what comes out. Maybe they do it differently where you are.

          • Um no. Its always a 10 kwhr battery. There are 10kwhr batteries with 92% efficiency. And there are 10kwhr batteries with 75% efficiency.
            Battery capacity does not change with efficiency. Output does.

            Just like the energy in a gallon of gasoline is about 32 kwhr equivalent. But the amount of energy you get out is much less because of efficiency.

            The amount of energy in a gallon of gasoline is always the same. This is chemistry and physics. Very dry stuff.

          • Clearly they do things differently where you are. Here for example, if a lead-acid car battery claims to be able to supply 50 amp-hours it has to be able to supply 50 amp-hours otherwise whoever sold it to you has to replace it or give you your money back.

          • An amp hour does not a kwhr make. And I am sure the that if you look at two batteries that have 100 Ahr, they could be the same. Charge. Or perhaps current. But not energy. There is efficiency to deal with.

            But I doubt that any official body is going to check to see if the energy stored in a capacitor is 1/2 C V squared or if the energy in a gallon of gasoline is 33khwr.

            And I am sure you have heard of lead acid batteries having 12.6V or so. But when they are run at their CCA rating, whats the voltage?

            So is it a 9V battery if you draw 5ma from it and you measure 7V or is it now a 7V battery?

            You could come up with your own unique standard of how to rate voltage sources, but we already have one. We use open circuit voltage and equivalent series resistance.

            Otherwise there is a different voltage rating for every load. That would make it awkward to compare sources.

            Likewise, rating energy storage sources by their energy after one way, or two way efficiency at different loads, currents, or other conditions creates a confusing mess. But rating this Redflow battery by its energy stored and efficiency is exactly what Tesla did. Until they decided to be real nice and post the energy after losses. That was a mistake. They should have left it the way it was, IMO.

            Nobody would have complained if they said it was 7 kwhr and 92% efficiency. If they didn’t get that, Telsa would have just said, you have to figure in the efficiency.

            Or maybe I am wrong. Even with a storage capacity and efficiency, maybe some would have said it should still be 7kwhr after efficiency is calculated. Then it would have been which efficiency. Round trip or single ended.

            And on we go.

          • You’re confused. If a car manufacturer says that a vehicle has a certain range, or its engine develops a certain power, you don’t next divide that number by ~3 for inherent inefficiencies. Those are already factored in.

            Same for batteries. All the specs I’ve ever come across, for lead-acid, Ni-Cd, Ni-MH and LiCo, measure capacity at the output.

            (Measuring “capacity” at the input makes no sense, except to give the designer an idea of the charging requirements, because then you could get infinite capacity with just a stupid wire).

          • So does it become a 6.8kwhr battery when I use it at lower current and it has less losses?

          • Ok. So I am confused. So lets make it simple. Forget fancy stuff. Its just a battery with resistance. A battery has a rating after efficiency thats 6.4kwhr. Its efficiency is 92%.

            So what is that thing called thats the rating before efficiency is applied?

            I think it comes out to 7kwhr.

            Enlighten me.

          • A 6.4 kW⋅h battery system with 92% round-trip efficiency means that you’ll have to provide 7 kW⋅h to fully charge it.

            10 kW⋅h and 75% means a full charge would take 13.3 kW⋅h.

            What matters is how much energy can then be retrieved out of either system: 6.4 and 10 kW⋅h respectively. Not which proportions of the losses go where (the battery cells, its cooling system, the electronics around it…) and when (charging, discharging, standby)…

          • Yes. We all know that. But thats not my question.
            My question is:

            What do you call (or name) X in this equation?

            X times efficiency = output

            where output is the energy output of a battery?

          • The battery will have a larger cell assembly, perhaps 10kwh. The ‘output’ would be 6.4kWh, assuming all losses are accounted for, so a ‘6.4kwh capacity battery’
            (specified at some particular load). In that case, there is no physical 7kWh to be claimed.
            If I take the argument that resistance (losses are not so simple as that), accounts for the lost 0.6kwh, that’s another situation.
            Say the resistor is fitted between the cell terminal and the battery output. There will be a voltage drop across that resistor for the specified load current, so load voltage will be less than the cell voltage; 0.6kwh is lost as heat.
            If the same (constant) current is used when charging, then the charging voltage must be greater than the cell voltage to account for the same voltage drop during discharge.
            Round trip losses would be 1.2kWh, not 0.6kwh.

            Most cells have low internal resistance. The charge/discharge voltage difference is small, and is often ignored, or Ah capacity only specified.
            Otherwise, the battery’s voltage efficiency (discharge_voltage /charge_voltage)% must stated. Energy efficiency is (colombic (Ah) x voltage efficiency)
            In flow batteries for example, voltage efficiency relates to flow rate, and can be quite low in those batteries.

          • So doesn’t that mean if the battery is run at much less current, more energy is obtained from it, and at the limit, if the current is low enough, it approaches 7kwr, ignoring quiescent currents?


            What do you call the quantity X?

            X times efficiency = output energy

          • If you like, but the cell capacity is much larger, unless DoD is implausibly high. The ‘7kwh’ has no particular reason to be stated, and there is no reference to DoD.
            ‘6.4kwh’ is not battery nor cell ‘capacity’, but usable energy. Batteries store charge. Ah is the measure of capacity. Charge is expressed as A ( 1A = 1Colomb/sec) for period (h). To turn charge into energy, there must be a load, which is the stated 2kW. It’s a moot point to claim that some tiny load justifies a ‘capacity’ that does independently exist.
            Capacity (Ah) *is* literally load dependent. It is not a fixed quantity BTW.
            There is also no reason to assume that the causes of the lost 0.6kWh will scale with load. As load is reduced, the losses may remain, or reduce slower, so efficiency could worsen. May be better, too. But then, the result would not meet the 2kW load specification.

            Stating 6.4kwh as ‘usable energy’ would be acceptable, even if the purchaser does not know the efficiency.
            But, then, 92.5% would be the ‘discharge efficiency’ and not the round-trip efficiency, which will be less.

            The specification is ambiguous. The manufacturer was not forced to state things the way they did,
            None of the above implies anything one way or the other about Redflow’s claims. Their specs are vague, too.

          • Yes. And well explained. But I was looking for an answer to the question.

            What do you call the quantity that exists before efficiency is applied?

            I have a problem with the output being stated as a simple number. There are too many conditions that change it.

            IMO, there is a consumer education issue here.

            Not that any of this is easier or better one way or another for the consumer trying to decide. Its easy for manufacturers to express data in ways that skew their numbers to their advantage.

            And I think this focuses too much on an issue that has less effect on the usefulness of lithium batteries than cycle life which varies much more due to conditions than efficiency.

            Redflow has other limitations that must be taken into consideration because its a flow. By contrast, Redflows specs don’t make abundantly clear the low efficiency, much less explain those implications for use.

          • Actually you can get 10kwhr out of it or nearly so. Since losses are proportional to current squared, you can lower your current. See the problem? Did the capacity change or did the current change? Same battery.

          • You’re erroneously assuming that all losses are resistive.

            By the same faulty logic, PV modules, LEDs etc should see their efficiencies skyrocket at low currents. They don’t.

          • Um, no, I am not assuming that. I am asking some questions and making a case for looking at it a different way. I know the PowerWall has a DC-DC in it. That has some quiescent current that skews efficiency at lower power draws.

            But put that aside for a minute and just look at a battery. Nothing else. Does its energy rating change when its used at lower current or not? Why does the same battery have a different energy rating depending on how its used? A raw battery is internal voltage and series resistance. There are a lot of other factors. Like temperature.

            So it comes down to this. Does the capacity rating vary with current? Temperature? More?

            Or do you rate it for energy and then factor all the losses.

            And just why is the efficiency rated at 2kw and round trip? Isn’t that arbitrary? Efficiency could have been rated at 3kw. Or 1kw.

            Is a 9V battery now a 7V battery because its got more current draw?

            Have we discovered that a car battery really isn’t 12V because its voltage is much less when its cranking the engine?

            Or is it still the same car battery with an internal resistance.

          • If not resistive losses, what were you thinking of by stating “losses are proportional to current squared” then??

            Large batteries typically have very low internal resistance (e.g. ~0.1 Ω for the 24 kW⋅h Leaf), and lithium chemistries boast high Coulombic efficiencies, so losses in the Tesla product are likely dominated by ancilary systems anyway: cooling pump, DC-DC, BMS…

          • I can’t say it any better than this:

            “Every battery has an internal resistance. You can think of an actual battery as a perfect battery in series with a resistor. As you charge the resistance converts some of your charging energy to heat. (note that watts = power = energy/time = Joules/sec). Say you’re charging a 10V battery at a rate of 100 watts (stored energy per time). For a perfect battery that would require you apply 10V at 10 Amps. But if the battery has a 1 ohm resistance you’d actually need to apply 11V meaning you’ll need to supply 110watts of power to get 100watts to the battery. The remaining 10 watts goes as waste heat. But that’s not all! You again loose energy discharging the battery. But that’s is a variable amount. If you drain the battery at low power for a long time you get better efficiency than if you drain it quickly at high power. ”


            A manufacturer with a lower series resistance battery might rate it at a higher power.

            Typically, a battery with lower series resistance has a higher power rating. But you could operate a batter with lower series resistance at the same power as one with high resistance and get a much better efficiency.

            “losses in the Tesla product are likely dominated by ancillary systems anyway: cooling pump, DC-DC, BMS…”

            This statement is unproven. I don’t think its correct. I did some calculations of Tesla battery packs and Panasonic cells. It looks to me like most of the loss in the 92% round trip spec must be internal resistance. You can work backward and figure out how low the internal resistance has to be and view the Panasonic cells and see what they are.

            A 7kwhr rated pack running at 400V has to have cells in a certain configuration. The likelihood that they are 96 in series at about 4.1V like the car is very high. That means we can also make and educated guess about how many are in parallel/series and what the equivalent pack resistance is.

            The 10kwhr pack is even clearer, since its the same chemistry as the car. The losses are dominated by internal resistance.

            400V, 25Ahr, cells are about 35mOhm each.

            (the literature says more like 65mOhm here)

            about 3 Ahr each.
            96 in series, 7 or 8 in parallel. That means the internal resistance is
            96/8 x 35 mOhm = 0.42 Ohm. Thats about a 10V drop on 400V, or about 2.5% loss. Stated another way, about 97.5% one way efficiency.

            (skewing most of the numbers in favor of lower resistance)

          • If we compare this flow battery and the Tesla battery equally, this battery is not a 10kwhr battery. In fact, since its one way efficiency is 75%, this battery is nowhere near 10kwhr. Its 5.62 khwr. Or really, its not even that, because according to the paper on the subject, its efficiency drops even lower than that at higher temperatures. And it will deliver that, but it needs 0.5 to 2 hours to refresh itself every 1 to 4 days. So it cannot operate just anytime.
            Does this mean this manufacturer is lying? IMO, not exactly. I don’t necessarily have a problem with their specs exactly, but I do find fault with their representatives claims being too broad vis a vis Tesla.
            They seemed to brag about lots of things but shy away from efficiency for some reason.

      • Thats correct. The amount of storage is the same. It never changes. The input and output efficiency both change with the load current.

      • Do you calculate your car costs based on warranty? If you own a Toyota, the warranty is up in 3 years. Thats a very expensive car. Now we don’t know how well Tesla will do compared to the warranty numbers, but to evaluate based on those is clearly wrong. The best we can say is we don’t really know. Unless we hazard some guesses from how the equipment is used.

        Here is what I say. If used correctly, the batteries can last far longer than that and perform far better. The key is to limit DoD effectively. Also, it helps if temperature is held within some limits.

        That leaves open a wide range of performance. IMO, thats the real reason for the pessimistic looking warranty numbers. Tesla should straighten that out with better control over use. But even a user can manage that. In grid tied applications there is no excuse for trashing the batteries.

        Its a choice similar to changing oil. Limit DoD (and time on full charge at high voltage) and extend life. Or not and ruin the battery.

        • One cannot forget the rate of input/discharge as well, vastly important 3rd parameter.

          • Yep. The resulting output is nothing like a fixed result. It depends continuously on other variables. Load current is a major effect.
            Company A rates its output at 1A. Looks great.
            Company B rates its output at 4A. Looks 16x worse.

            Compare the specced efficiencies? Not going to give the real picture. Not unless one knows a great deal more.

          • Was moreso speaking to points of degradation, not an easy means of comparison.

          • True. It requires deeper analysis that just a fixed output energy at initial use. Much more sophisticated than that.

            Cycle life is extremely variable depending on DoD. Estimations of efficiency pale in comparison to those effects.

            The cost of energy depends a great deal on cycle life. Cycle life varies by multiples as much as 5 or more.


        • @vensonata was pointing out how expensive the Redflow battery was per cycle over its warranty period. If that is the metric we choose to use, then it should be applied to all manufacturers the same way.

          “Cost per warrantied kW⋅h” may be pessimistic, but it’s a fair assessment, based on tangible, verifiable and actionable data, not merely speculation or non-binding marketing fluff.

          Say you’ve got to chose between 2 products from different manufacturers, but having otherwise the same specs and price. Neither manufacturer has sold such products before.
          Mfg A says “It should last 20 years!” but guarantees 5.
          Mfg B guarantees 10 years.
          Which would you choose?

          • You tell me. Toyota is 3 year 36k, Hyundai is 5 year 100k. Which is better?

      • Nope. Tesla at the most pessimistic is nearly half the price per kwh. Even at jacked up Australian prices of $8000 for the battery alone. Lets convert to U.S. $6145 today (australian dollar recently risen). The total minimum warranted kwh of the Powerwall is 18,000 over ten years (740×5.4 + 1087×4.6 + 2368×3.8 = 17,994.6 kwh) $6145 divided by 17994.6 = 34 cents per kwh. That is the worst case scenario possible. Which do you think the bigger number is? 61cents or 34 cents?

        • Yes, Add this. A couple of flaws in that warranty curve above.

          1. Warranty does not equal performance. In order for a manufacturer to survive, most of the products have to exceed warranty. Only a few outliers fail. That means the actual performance must be considerably better, enough to limit failures.
          2.No real product would have a performance that steps like that over time.
          Start at 6.4kwhr and go down to 5kwhr for a more reasonable estimate at least, IMO. Notice that this is 80%, exactly the standard degradation used for batteries. Notice that the end time is arbitrarily rated as zero output. Thats false. Those batteries could be used much longer. And the real question is how far they would go to 80%. They might go out to 15 years,
          3. Payback is calculated based on output, not input. And efficiency varies with output, rising rapidly at lower currents. In all likelihood, both charge and discharge will be at much lower levels than maximum rated. In any case, in grid tie, the most common app, there is no need to run at max current, lowest efficiency. In fact, to get the greatest payback, it needs to be programmed to have steady charge and discharge.
          So the 6.4kwhr rating is wrong as a measure of output energy anyway to begin with.
          We are probably talking more like 15 years to 80% starting from an average of over 6.7khwr and falling to about 5.4kwhr.
          4. Lets suppose the battery failed to meet warranty in the first few years. The battery would be replaced and the performance would start anew above the line.

          That makes a completely different calculation. And the elephant in the room is how many cycles, not what efficiency.

          This poor analysis seems to come from one website with a catchy, misleading headline. Its a disservice.

          The stupidity of this analysis assuming that the performance is equal to warranty is that you would have to have a battery that just barely performed above that curve in order for it to be valid. Just step one bit below it, and bam, replacement.

          • The stepped chart is a direct interpretation of the written warranty claims. In reality, the total accumulated discharge will be around16MWh. Draw a line between 100% and 60%.
            The mid-point mean is 80%, so 18.7MWh of the expected 6.4kWh x 3650 total. The actual curve described by the written data points lies below that line, resulting in 16.4MWh.

          • See my calculations above, I believe it is more accurate than your numbers. The curve is not straight but flattens out below 85% down to 60%.

          • After some reflection, here is what the warranty is saying: 6.4 kwh for two years to 85% minimum.(5.4) 85% descending to 72% minimum for the next 3 years.(4.6) Then 72% to 60%(3.8) requires 6.5 years. Total 21,473 kwh with 60% remaining. The total cycle number is actually 11.5 years or 4194 cycles. That is the warrantied minimum. So an expectation of 5000 cycles at 13.7 years is quite reasonable and what Musk indicated.
            At 21,473 kwh for $3000, that is 14cents kwh. That includes nothing but the retail price of the battery.
            Now Tesla could not possibly shave their promise that close to optimal…in other words they have to be certain they won’t have to pay for that battery replacement. So they need a margin of error of what? 20%? 50%. Anybody’s guess. But at 20% above warranty is 11.5 cents kwh and at 50% above warranty it is 9.3 cents kwh.

            Again, this number is strictly for battery comparison and does not include install, inverter etc.

          • Yes. Nice job, vensonata. It appears conservative enough to guarantee PowerWall will meet warranty. My chief concern is that DoD has to be properly limited to get the cycle life necessary. No 100% DoD allowed for a lithium battery.
            The Redflow battery has a different analysis. They don’t appear to be guaranteeing a whole lot more lifetime khwr by warranty.
            Here is a white paper on field use for the ZBM. Doesn’t sound like it pays off there, either.
            Here is a paper from Redflow.
            Here is the Redflow warranty. ZBM2 30kwhr, ZBM3 33khwr.
            Since even the most expensive estimates of the PowerWall are about 6k, and the Redflow is in the neighborhood of 18k, Redflow is more expensive.

          • Right, I looked at the Sandia lab testing of the Redflow. All in all the battery is alright…just about 4 times too expensive. What can I say? The math is simple enough.

          • Same. I like flow and I want it to succeed. The cost is no quite there yet.

            A bit surprised that few noticed or objected to the working fluid toxicity. A bromine battery failed at an EV race quite a number of years ago. After that, they banned them.
            I trust they have this better sorted out, but, IMO, its best for users to have this in a non regularly habited space, with some ventilation.
            Just like I think its best for users of lithium batteries to have some kind of smoke detectors or a heat sensor that can shut off power and a handy fire extinguisher. Not mandatory. But wise.

            I like the Aquion and some of the others for toxicity and fire, but some of those alternates are not doing so well unfortunately.

          • Written capacity fade is 85%, 72%, 60%.
            Close to (100%x85%) = 85%, (85% x 85%) = 72%,
            (85% x 72%) =60%. Plotted as a continuous function, the integral is ~70% of that expected from 100% retention. Aggregate is ~16.35MWh. Because the battery is marketed for ‘daily’ use, then unlike cells or general batteries, the warranty is expressed in years, rather than cycles.

            Capacity fade is the result of secondary chemical reactions, mechanical degradation of the electrodes etc. The warranty is derived from a model that predicts capacity fade from those effects, when cycled daily.
            The curve does ‘flatten out’ , but that is because the relative decrease in capacity becomes smaller, because capacity becomes smaller, so takes more time to accumulate the same amount. 70% is simply the ‘area under the curve’.
            The chosen sample points have no relevance other than to to describe the result in simplified written form.

            The battery shows significant decline from the beginning of life and that is the reason for the smaller than expected aggregate.

            “But at 20% above warranty is 11.5 cents kwh and at 50% above warranty it is 9.3 cents kwh”

            Adding 20% to the EOL of 60%, won’t reduce kwh cost by 20%. Because, if 30% is lost when EOL is 60%, it is perhaps easy to see that raising the EOL by 20%, can’t reduce the lost total by 20%. As an example, assume linear capacity fade.
            EOL 60%. Mid-point capacity = 80%, 18.68MWh.
            Add ‘20% tolerance’ to the 60% = 72%

            EOL 72% .Mid-point capacity = 86%, 20.08MWh (+7.5%)

            The battery can be used after 10 years of course, but then
            accumulation simply takes longer and longer, so is not very useful. Aggregate storage, and how long that takes, are points to note when considering a warranty.

    • But they said it was better than Tesla. What does that mean?

    • Actually they usually rate throughput as the output, so the .75 multiplier isn’t applied after, but before, so compared to Tesla(.925) you lose 17.5% input, but not output.
      You can only properly compare it to Tesla’s 7kWh NMC battery, so when made equivalent in size with Tesla’s warranty being 25.7MWh(25,714kWh)(3,779cycles) vs. Redflow being 30MWh(30,000kWh)(3,000cycles)
      Basically you get 16% more output within the 10 year warranty but with the aforementioned 17.5% input efficiency loss it’s negated. At $13,810 compared to $4285 which an equivalent Tesla 10kWh NMC would cost I’ll surely pass until that warranty doubles in both years and throughput. Also there is the fact Powerwall 2.0 is just around the corner so the equivalence will be under $4,000 soon for Telsa.
      In Australia the numbers are much different than North America, the LG Resu currently beats out Tesla’s 7kWh, mainly due to shipping cost differential and cycles.
      In the North America and following Powerwall 2.0 elsewhere Tesla will hold the lead for some time.

      • $10 US should be more than what it costs to ship 100 kilograms from the US to Australia at the moment. So just shipping alone does not account for much.

        • $10 for 100 kg eh, I guess in bulk the prices sink drastically.
          Still the 7kWh Powerwall is double the price over there as in the US, $3,000USD vs $6,100USD. Seems pretty sharp.

          • Sorry, that is for bulk shipping. I just mentioned 100 kilograms because that’s what the Powerwall weighs, plus whatever its packaging is. Tesla might pay a premium for faster shipping, but that’s not going to cost that much more. And yes, the increase in price over $3,000 US in Australia is pretty sharp.

      • RESU might beat Powewall on claimed numbers and warranty. But just like Hyundai has a longer warranty than Toyota, I wouldn’t bank on it meaning too much.

    • Lead acid has similar efficiency round trip. Basically you can get 10 kwh crammed into the battery but it takes 12.5 kwh to do it. This is standard battery stuff. Of course other factors like “acceptance” are very important too. It is why lead acid batteries “suck” as Musk proclaimed. As they approach 85% full they can only accept a trickle. And your precious solar is being wasted. I presume this redflow does a better job with rapid acceptance to 100% full.

    • Yes, but you’ll never have to worry about a Redflow battery going hoverboard on you.

  • When enthusiasm exceeds reality. This is a financial blackhole that you won’t recover from when you buy this contraption. It doesn’t make economic sense, so why buy it?

    One can easily compute if it will pay for itself during its life span if you know the electricity rates charged by your utility. In the case of our local rates, payoff will never happen.

    • Off-grid applications are pretty significant, I know a number of regions in the province next to me where there is no grid infrastructure and people rely heavily on generators. Pretty sure the cost per kwh of these batteries is lower than a diesel generator.

    • “It doesn’t make economic sense, so why buy it?”

      As the article says, some people buy things to be part of the solution and to help that solution drop in price, even if it costs more now.

      • Its jumping the gun to say it doesn’t make economic sense. Under what conditions? And what happens when distributors lower prices to compete? We are talking about a product in hot demand that has just entered the market. Just exactly what other systems are competing with it and what are their prices? I hear a lot of claims, but no numbers showing alternatives are lower in cost.

      • 😀

    • Talk is cheap. Even less than base rates before tier. But CPUC just increased the rates.

  • Hackett says the driver for battery storage is the same that inspired people to buy the Prius hybrid vehicle.

    Nope. The Prius was a no-brainer: it saved money and reduced pollution.
    Battery systems do the exact opposite.

    • Please explain how the do the opposite of reduced pollution? If they are being used to move power generated by solar during the day and has it being used at night when the bulk of an area’s power is likely coming from Coal, NG or Nuclear? As for money it could depend on your area. Someone was talking about power cost could sometimes get as high as $1 per kWh in Australia with other times they are almost paying you to use power because of a surplus. In the end this could also be considered a luxury item. Some people don’t want to be without power and in some area’s the power grid just isn’t stable.

      • Yes. Medical needs and refrigeration can be costly items to do without in a power outage. What’s that cost? When you stack up the benefits and look at how electricity will cost more than the base rate due to TOU in the future, the value looks different.

  • We now have information from Australia on how the Tesla Powerwall partakes of perspiration from a deceased pirate’s cannon shot:

    Note the Tesla Powerwall itself does not inherently partake of perspiration from a deceased pirate’s cannon shot. If it had simply appeared exactly as it is it would just be one more entrant in the field of home and business energy storage and would be appreciated as one more available option. No, it was the promises that were made and not met that make the Powerwall partake of perspiration from a deceased pirate’s cannon shot.

    If Tesla had merely announced that it was entering the field without making promises, then we would be hopeful that the product would be revolutionary as Tesla’s cars have proved to be, but we wouldn’t be able to complain when that turned out not to be the case. But now we can complain. A lot.

    Hopefully Tesla has learned from this debacle.

    • Whats the warranted cost per mile of a car? 50k warranty? $1 a mile?
      Sorry. Warranted cost doesn’t make sense. Manufacturers can warrant high or low. It does not correlate well with actual performance.

      A Toyota has a 3 year 36k mile warranty.
      So does VW. But parts are only good for a year.
      Hyundai has a 5 year 60k mile warranty.

      From this we might conclude Toyotas are unreliable and Hyundai is a more reliable car. Or not.

      And VW parts are so bad that they only last one year. Or not.

      IMO. Something has to be learned about what warranty really means.

      Also. Is a 7kwhr battery with 92% efficiency the same as a 6.4kwhr battery?

      I dont agree that a 7kwhr battery better deliver 7kwhr. Thats a misunderstanding. Its the same energy capacity whether its 92% or 50% efficient. And the efficiency varies with load. The capacity does not.

      When lithium batteries came on the market, DIYers hooked them up like lead acid and watched them die early and complained. They hooked up batteries from different manufacturers with different voltages.

      Using a lithium battery without BMS, cell balancing, temperature regulation, and discharge limiting is like running your car for 50k miles without changing the oil. You might as well throw it away.

      The conservative warranty reflect Telsas uncertainty about how users will treat the battery. And a new product not yet used in the field. We may find like the Leaf, that areas like Arizona don’t work well with batteries without cooling systems. Its as yet unknown from field data.

      • There are a variety of methods I could use to attempt to judge the likely lifespan of an energy storage system. I could make an estimate from looking at it. Or I could listen to what sort of sound it makes when I shake it. Or I could lick it and try to gauge its expected lifespan from its taste.

        But for now I think I’ll base my expectations of how long a system is likely to last based upon its warranty. Because as of the moment, people who design, build, and test energy storage systems and then back their expectations in with with money in the form of a replacement should it fail to perform as their warranty promises, probably have a better idea of how long a storage system is likely to last than my olfactory and other receptors can pick up from an examination. And until I have a good reason not to, I will continue to base estimates of the overall cost of energy storage systems on their warranties. I am quite simply a warranty bigot and I will continue to discriminate between energy storage systems simply on the basis of their warranty without any compassion or remorse.

        • You would base a judgment on how long a battery would last based on warranty. But not a car.
          So wouldn’t you assume that a battery would perform much better than its warranty like a car would last much longer than its warranty?
          Or that the warranty itself is a very loose connection to actual quality or performance?
          Or that it might not make sense to judge Toyota of inferior performance or quality compared to Hyundai based on warranty?

          • As I’ve said before, warranties guard against failure and merely estimate product life, usually to the 50-60% quality mark.
            Consumers will be glad some day how much they underestimated the quality of these things.
            I really think a smart battery company would over-estimate their warranty, as by the time a replacement is needed it will cost them <40% it initially did to produce. Volume is growing such that lowballing is just screwing yourself out of sale and growth. They think they're playing it safe to not have to default, but in fact their sales could be double and the default could cost a 5th of that gain.

          • “I really think a smart battery company would over-estimate their warranty, as by the time a replacement is needed it will cost them <40% it initially did to produce."

            That can be true if you don't look at the risk that failure rate data is not correct. For example a vendor produces one part that doesn't meet spec doubling the failure rate during the warranty period. This will greatly increase cost to the company and lower the reputation of the company and impact sales.

            A small error in one part could dramatically inpact a companies profitability. and vocationally will send a company into bankruptcy. So as fare as company is concerned being very conservative with a short warranty is better than being aggressive with a long warranty.

          • Faulty parts aside, going long in the battery market will win you more clients, most of which won’t even put the system under maximum stress.
            I say, test the exact product for a 3rd of it’s product life, warranty 2/3rds, increase your sales and by the time you ‘pay out’ on the failures and warranty claims the product cost you <40% to make.
            For example, if you had 10% of consumers sink below your warrantied parameters, on 40,000 units costing $1 to produce(hypothetical);
            Your product more than likely has a 25% profit margin, say this long warranty garnered you conservatively 35% more sales.
            So you would have sold ~30,000 units at a $7,500 profit, but instead sold 40,000 yielding $10,000. Since you made these units 5-10 years ago the price to do so has dropped to 40 cents, completely replacing that 10% warrantied will cost you $1,600, so you netted a gain even off those initial sales and since then your increased company growth has compounded into a possible $5,000 winfall not being stifled by competitors.
            Warranties are like playing Poker, a small bluff can lead to a big win.

          • I am used to battery warranties from various flooded lead acid and AGM that I have had over the last 15 years. The warranties are trivial usually. Lifespans are usually twice the base. Only a few industrial grade lead acid batteries have 10 year warranties but many report more than twenty year lifespans in actual use. Lithium banks haven’t been around long enough to really know from experience and they keep improving yearly so, welcome to uncertainty.
            What is fairly accurate are the lifecycle curves for lead acid that I have used. As long as operated properly those published curves seem fair. But they aren’t part of the warranty.
            What Tesla does not publish is a lifecycle chart. Their warranty is a strange jagged step down that I find simply strange. However my guess is it is extremely conservative and protects them from any unexpected glitches. I presume, if nobody buys it because they take the warranty data as the real life performance, then Tesla will change the warranty data. Note that they simply vanished the 10 kwh powerwall since nobody wanted it apparently.

          • Yes. There is a huge range of results depending on use and care. The old story of the guy changing his oil often and driving a million miles. Or maybe its a myth.
            But the thing with those long lasting LA batteries you know as well as anyone. Keep them in their sweet spot and maintain them. But you can’t use them all out. They need to be babied a bit.

  • But is it cheaper than Imergy or Aquion batteries?

    I think not.

    The cycle life is too short on this Aussie battery.

  • I actually enquired about the RedFlow in .za

    The local agent ProbeGroup were quick to send me the PDF’s with the same information from the RedFlow website, but the promised price quote never came.
    Interestingly they hadn’t even fixed the stock PDF’s. They were full of “Insert Logo here” and “Insert Company Details here”.

    They’ll need to do a much better job of pursuing customers than they are now if they want sales.

    Looks like the AU$ pricing will make it less reasonable than other options though.

    • Or misspelling on their web pages….

  • Mr. Hackett, when will you be coming to America. Nationwide Solar and others want to offer your product to the American market. We don’t need Tesla’s Li-ion chemistry here. What we need is Redflow.

  • I do think there will likely be a spot for flow batteries in the stationary market. But not sure this is the price or product to grab it. The ability to add another tank to get longer storage that you don’t use often make flow “feel” like it should be able to find a spot.

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