A good boost converter will be ~90% efficient (it can be more efficient, but not miniaturized like the pictures show). So, to begin with, you'll discard ~10% of your energy.
Indeed if you gadget reports the batteries as dead at 1.25V, you can still get ~40% more usage. But most gadgets don't work that way. 1.25V is the normal voltage of a fully charged NiMH rechargeable AA, so if you gadget works with those, the real cutoff point is likely closer to 1.15V or so.
The booster will boost the voltage (at the expense of current, obviously, plus losses) so that even though the battery will be below 1.15V, output voltage will be at 1.5V. Looking at the graphs, this buys you less than 1/5th, and if you consider the losses in the boost converter, probably half that.
The "800%" claim seems totally bogus. Perhaps with a gadget that stops working when the voltage falls below 1.45V per cell.
I'm not saying it's not a useful gadget (and I'm very impressed by the miniaturization: where is the inductor? This thing must run at several MHz at least!) — just that the claims should be taken with a large grain of salt.
Perhaps with a gadget that stops working when the voltage falls below 1.45V per cell.
And such a gadget is one that no one would buy, and consequently no one would produce. Electronics designed to run off AA batteries already extract as much energy as is practical from them. From those discharge curves you can see that there is a gentle downward-sloping section, followed by a distinct "knee" at the end where the voltage falls rapidly. That is where the gadget would be designed to work down to.
Sure there's a few percent more beyond that, but adding a boost converter which attempts to extract that energy won't work - the boost converter itself will be consuming energy, and likely far more than is available past the knee, so this device could actually reduce how long your batteries last!
As for the miniaturisation - this isn't that small; similar boosters have been present in MP3 players, cellphones, and other battery-powered electronics for years. Fitting everything on a PCB with the diameter of an AA and less than 1mm thick is not that hard. Look at the ISL9113A for one example. I haven't laid out a boost converter in a design with that space constraint, but it turns out to be roughly of that area anyway and I'm sure if you did things like cutouts to sit the passives into the board, it'll be thin enough.
And such a gadget is one that no one would buy, and consequently no one would produce. Electronics designed to run off AA batteries already extract as much energy as is practical from them.
Indeed. If your gadget can make use of NiMH rechargables, then you're already having to deal with about 1.2V per cell, and that's when they're fully charged!
So if you need 3.0V or 3.3V nominal for your main supply, you are probably already using a buck/boost switching regulator. As long as the battery can supply enough current, your gadget will keep going, and drain pretty much all the useful energy from it.
Regarding efficiency, you should simply add the batterizer thing only after your new batteries became "dead" for your appliance. This way you use the normal run of the battery at 100% efficiency, and everything extracted after that is pure gain.
This may be naive, but would it be possible for the voltage booster to only start 'boosting' after the battery falls under a certain voltage threshold? That would be seem to solve both of your concerns.
The trouble is that the battery doesn't know the voltage requirements of the device it's powering. Should it start boosting at 1.4V? Or 1.25V? I have a hunch that it already does this for voltages near 1.5. The trouble is determining where you draw the line.
But they don't control the IP for the actual boost circuitry. Thats trivially easy to do. And from the comments in this thread it seems like lots of electronics already do it.
Maybe "bogus" is to strong but I would say "suspect".
The "proof" in the article could be summed up as:
1) A demo to the writer which (and I'm not suggesting this is what happened) any magician could have pulled off
2) A statement from an authority source "Dr. Kiumars Parvi" "with the physics department of San Jose State University" who said "we confirmed that the Batteriser taps into 80 percent of energy that is usually thrown away"
Neither item confirms anything like 800% nor do I remember seeing any independent testing to prove that point.
The article briefly mentions using them with rechargeable batteries. While I'm sure the boost to 1.5V allows more devices to use the rechargeable batteries, I'd be concerned about over-discharging [1] NiMH batteries.
Internal resistance rises ridiculously fast with depth of discharge but even in the range of "ohms" you can still squeeze out a good fraction of an amp, a decent fraction of a watt. Its surprising how much you can do with a tenth of a watt or whatever, this will work quite well with a remote control or wireless game controller or a kitchen timer, maybe not so well with RC cars or laptop power supplies or the stereotypical "charge your cellphone with a AA battery" product or 1000 lumen flashlights.
In the long run nobody's ever going to use cells in series so as to avoid depolarization / cell reversal type stuff. Its feasible now for low current stuff, what I'm getting at is "someday" people will be running portable drills off single cells. Its a long term trend in power conditioning.
I am similarly skeptical. I contacted the physicist quoted in the article and inquired about the tests they did in their lab. I wanted to see if the quote is out of context, relates to a specific use case or what. He sent a brief, friendly reply (from his iPhone). Here it is:
Dear [redacted]
Thank you for your email concerning the Battereiser. The product is sound and we will disclose additional information in the coming weeks.
Best,
Kiumars Parvin
So he is apparently still endorsing it. I still suspect the article is grossly misrepresenting its usefulness. I am willing to be swayed by solid data, but I'm not holding my breath.
How can other posters take this article at face value? This reads 100% like a fake ad (I mean stylistically and in terms of presentation, like the kind of thing you see "Advertisement" written in small text over the top of while it's run in the New Yorker or wherever. I read them. I like it. Because they're amusing.) The only thing that keeps it from being one is that it's on macworld.com. Like, really? Industrial espionage, a real "professional job"? "Big Battery"? Everyone here has worked on way more interesting technology than a metal sleeve and a farfetched tale - which is all this is - and who breaks into our offices to steal our tech? It doesn't happen. Nobody would do it even if the device works exactly as stated.
Do these prototypes look to you like something that came out of a test lab? The only work put into them is the branding, "Batteriser" a word that is mentioned 43 times in 2000 words, including the first word of the title.
I'm not calling this native advertising but if it isn't, it seems the only one more gullible than this journalist is everyone else who swallows this hook, line, and sinker.
You could have written the same article but with some doohickey that lowers gas mileage by increasing oxygen mixture, and gets stolen in a brazen act of industrial espionage, a real professional job.
come on. we're adults here. this article is insulting. Where are the details of the break-in, such as date or what precisely was stolen, or where it happened - you know: journalism?
I was thinking if I lowered the RF exposure from my cell phone using one of those stickers you put on the battery, using some magic battery gadget in combination might very well turn my phone into a perpetual energy device.
Hey, man, I know people who will swear the 100mpg carburetor is real. They almost bought one, but then some strange men came and shut down the garage and when it reopened the new owner knew nothing about it.
> like the kind of thing you see "Advertisement" written in small text over the top
After the first 2 paragraphs I was searching all over that exact text. I turned off ad block, thinking it might be hidden. I searched and searched and saw nothing.
Because those other posters have used boost convertors in the past (as long as say 8 years ago?)...
Whether or not the efficiency claims hold up is something to wonder about but the basic principle works just fine and you can slap one together on a breadboard for a few $.
I make exceptions for really clever ones, but I think these low-effort comments fail the substance test[1]. If you encourage this stuff you'll start to see karma trains like the other commenter tried to start, and it won't be long before you have to scroll past the puns and maymays in order to read anything of substance like you do on Reddit (save for some subreddits that are aggressively moderated for serious replies).
Aggressively moderated subs like /r/askscience enforce the content rule for top-level comments, not children. It works there because you can collapse a thread very easily, unlike HN.
The reason for leaks is that as batteries discharge — either through usage or gradual self-discharge — the chemistry of the cells changes and some hydrogen gas is generated. This out-gassing increases pressure in the battery. Eventually, the excess pressure either ruptures the insulating seals at the end of the battery, or the outer metal canister, or both.
In other words by extracting more energy, there is more hydrogen evolved and it will increase their tendency to leak.
This was also posted on an EE forum I frequent, and the opinions on it so far have been mostly negative:
IMHO rechargeable lithium is the way to go. An 18650 has several times the energy of an AA while being not much bigger, and can be recharged. They're still not all that common in the West, but equipment like torches, power banks, and portable fans which take 18650s are gaining in popularity.
>equipment like torches, power banks, and portable fans which take 18650s are gaining in popularity
Don't forget e-cigarette mods (power sources). I'd wager they're the most popular application of free-standing (not packaged in a pack) rechargeable cylindrical lithium cells (I have 12 of them personally).
Yeah, if there's one thing I've learned from mechanical mods, it's that I don't want to over-discharge my cells. I'm guessing that your average AA cell won't fail as catastrophically as an unprotected lithium battery due to chemistry but I'd still prefer rechargeables (for most everything) to an endless stream of disposable alkaline batteries (even if I were able to squeeze a little more out of each one).
Lithium definitely isn't as resistant as alkaline to abuse, which is why consumer adoption (at least in the West) has been rather slow. Regular AAs don't catch fire or get dangerously hot when short-circuited, but that's also partly because they don't have the energy to.
Cylindrical hard-cased cells like 18650s are still safer than pouch-cell lipos though.
Deep discharge does not make LiIon cells explode (or vent), it only reduces their cycle life a bit. Though personally, I swap the batteries in mech way earlier than the point where they start getting damaged. At 3.6-3.7V the battery is weak and doesn't produce enough power on the coil. I'd be surprised if people regularly overdischarged batteries.
And the 18650 is about to be produced on a massive scale in the Tesla Gigafactory.
Personally I've recently switched from conventional AA rechargeable NiMH batteries to low self-discharge NiMH batteries (branded Eneloop) and am very impressed - things like my keyboard and mouse were needing to be recharged every 2 days or so and now I can go 2 weeks or more.
If you have enough light in the room a solar keyboard is also pretty awesome, I had one for the longest time. Kept it until I accidentally broke the keys cleaning it. Keyboard selection is very much based on taste though, so I assume you probably saw one and didn't like it.
I've got a big pile of Eneloop batteries; I've even pretty much swapped out the old generation for the new low-discharge generation by sheer use and wearing out the old set. It takes a lot but it can be done.
And I can't help but notice that if you take this at face value and this really does multiply alkaline battery life by 8, the economics still roughly work out as a tie with existing NiMH batteries in terms of cost... and if the tech fails to do 8x, which I tend to agree is quite likely for the vast bulk of uses, it still leans in favor of NiMH for most things.
Agreed on the greatness of Eneloop: I've used these in my Bluetooth keyboard and mouse for a few years now, and they also do a very neat USB-powered charger.
(Other brands do low self-discharge MiMH batteries too -- e.g. Duracell -- but I've had much less luck with those).
I use 14500's in my smaller flashlights. They are the same size as a AA battery. You can also get a 14440 to replace a AAA. (Of course the device needs to be able to deal with the 3.7v batteries.)
Back in 2001 I was designing mp3 players with boost converters in them that could start switching from a battery as low as 0.9V. It was hard to find boost converters in 2001 that worked down to 0.9V. It's obviously not hard to find them in 2015.
Any product that is evaluated on it's battery life already has very efficient boost converters built into it. Battery life is priority #1 for any battery powered product design team. It's agonized over in every design decision from the very 1st schematic.
About the only products that don't seem to give a shit about battery life are toys. Toy designers know that you are not making buy/don't-buy decisions based on battery life, when you're looking at a toy in the store. Toy designers cost optimize their circuits aggressively, at the expense of battery life. They deserve a special place in hell for that. This product would benefit many toys. Not much else, though.
They lasted a long time on just one AA or AAA cell. The SoC had the boost converters integrated into it, and from what I remember could work down to ~0.85V.
"Batteriser can continue to deliver a 1.5 volt charge in batteries that have discharged down to 0.6 volts. There are more than eight 0.1 volt steps between 0.6 and 1.5 volts, so, in grossly simplified terms, the Batteriser can extend operational battery life somewhere around a factor of eight."
They explained right after that how you get more amp-hours at each voltage step. The math works for that, though I don't think it fits the actual behavior of the discharge curve past 1.1 volts...
If this is such a great idea why isn't the circuit integrated into the devices that use batteries? I'm sure it wouldn't be difficult monitor the discharge rate and kick in the circuit when it's needed and the battery has demonstrated that it's an alkaline by its discharge profile.
It often is. Newer LED flashlights that run off a single alkaline cell always have a boost converter. Electronics that run off 3 cells often have a buck converter down to 3.3V or a lower voltage, which accomplishes the same thing, often a little more efficiently.
Boost converters from single cell alkaline batteries up to useful voltages are usually quite inefficient.
If you see something powered by two cells, it might not have a voltage converter because a lot of circuits can operate off that voltage directly.
If you use this sleeve inside a device with a built in voltage converter, you waste some energy, and your device gets confused about remaining battery life.
Because all batteries are is a tiny pile of two substances wrapped in metal. Adding any sort of electronic circuit increases the cost tenfold(or more).
9 - draws too much current when not in use. Theres some icom radio battery holders that are "famously" active, you can run a portable mobile radio (think hand held police radio or ham radio) on 2 AA batteries but the upconverter runs 24x7 once the batteries are installed so in 6 months, even if never used, the batteries are dead and in a year they're leaking. Think of the remote control for a TV that dies annually no matter how much or little you use it, all the amphours went into standby losses, operation energy was a rounding error. You can't run an upconverter for free, although technology is improving etc etc. Of course lower losses imply higher impedances which generally result in higher static sensitivity.
10 - "everyone knows" overdrained batteries leak, cheaper ones worse than the expensive ones.
0 - "Our technology is really a miniaturization technique that allows us to build the sleeve..., but the key is we’ve been able to miniaturize the boost circuit to a point that no one else has been able to achieve"
9 - It's more expensive, the market won't tolerate a price rise on disposable batteries, they cannot sustain a 8x average life of their product at current prices.
Tin foil hat mode: The battery industry makes money from selling in disposable battery volume; if their disposable batteries last twice as long, their sales volume will drop by half.
Of course, if they manage to sell their 2x lifetime batteries for twice the price it would sorta even out again. But the customer, when faced with regular batteries and 2x priced batteries, will still pick the cheaper one despite the lifetime claims.
Yes but he's asking why the DEVICES don't incorporate the technology. If for example Apple could claim 8x battery life in their keyboard by adding a 10cent piece of kit you'd think they'd do it.
To fit the booster into the same space as a battery is cutting-edge, but to put a cubic-centimeter boost circuit next to your battery chamber is nothing special. If the boost circuit is too bulky, the battery is definitely too bulky.
A boost converter is a very common circuit. If electronics manufacturers could extend the battery life of their products they would. Many products are regulated to require certain number of years that their batteries must last. Smoke alarms sold in California must have a 10 year battery. If they could use smaller batteries to supply ten years of power, a product with that large of a volume could save millions of dollars a year. Financial motivation is a two way street.
“The time it takes for the battery voltage to drop by
0.1V is longer at lower voltages versus at higher
voltages. That means that if a constant current was drawn
from the battery, it would take the battery a lot longer
to discharge from 1.2V to 1.1V than it would from 1.5V to
1.4V. This means that the extent to which the battery
life is increased could be even higher.”
Sure, but if you're drawing 20mA at 1.5v, you only need to draw 20mA from a 1.5v battery. If the battery drops to 1.2 volts, for constant power output you'll need to pull 25mA into the boost converter.
The article reads like a scam for exactly this reason. Sure, if you scale the power you draw from the battery as the voltage drops then I don't doubt you get a 8x increase in battery life.
But if you keep your power draw constant - ie. you're actually powering something useful from your battery - then current draw must rise as the voltage falls, and it will fall asymptotically. I can't see you getting anywhere near 8x; more like 1.5x. If that.
I do think that the claims made by Macworld are somewhat exaggerated. This kind of journalism always needs to be taken with some grains of salt. The paragraph in which the 800% extension is described, sounds messy, and doesn't cohere with some other claims made in the article.
The motivation of the story, namely that of a robbery of private documents, seems odd, and I can understand that it will immediately raise red flags among readers.
Some other points in the article did seem plausible to me. Modern electronics need stable voltages to keep working properly. The working of voltage regulators is well understood. Only the miniaturization is the invention, which is patented (https://www.google.com/patents/US20120121943), and has a very verbose application compared to other patents. There can of course be issues with the technology, of which theories are offered by some commenters.
For some theories that commenters are offering, an elaborate conspiracy would be required, building up references and trust, only to mislead absolutely and quite likely not get away with it.
Of course, conspiracies exist, but please don't think so lightly about arguing them.
Just want to note there is both a Frankie and Bob Roohparvar. They are the cofounders of Batteriser/Batteroo. Bob's the CEO. Frankie's the Chairman (he's also the CEO at Skyera).[0][1]
---
[0]: It's on the front page of the company's "website" @ http://batteriser.com -- which is really a redirect to a page on a different domain -- and Frankie is said to have 500+ patents.
[1]: Quick Google searching led to his linkedin page, and various other results, like Bloomberg research.
[EDIT: clarity & wording (...and now fixing formatting mistakes)]
My thouths exactly. Looks like the patent[1] is more about the sleeve than the actual circuit (because well, I guess it would/should be hard to patent Joule thief[2]).
I was wondering about that. I set one of those up a few years ago on a breadboard. It was a fun project (for this non hardware guy) and somehow very satisfying to watch a "dead" AA power a bright blue LED for weeks.
I wonder how the device will perform in the real world. Where do I sign up for announcements?
Why would I want to buy this gadget compared to investing my money in rechargeable batteries? I would probably use non-rechargeables for smoke detectors only.
Also the environmental impact is less with rechargeable batteries[1]
NiMH batteries compared to alkaline batteries cause
about 96 times less damage to
each of the three damage criteria (for 400 cycles).
So even if batteriser allows alkalines to be used 8 times longer, rechargeable (NiMH) batteries would still be 12 times better than that for these three criterias (human health, ecosystem quality and resources).
So, the same exact article appears on PCWorld, at the exact URL (just change the domain's 'mac' > 'pc'). Is that normal? I never visit either site, so I'm unfamiliar how much cross-posted content it/they feature across both domains.[0]
Curiously, http://comingsoon-tech.com (sans path) redirects to http://agency20.com, an agency that describes itself as offering "bespoke crowdfunding strategy ... as a way for creative professionals and entrepreneurs to successfully fund & grow their projects, while retaining 100% ownership and creative control."[2][4]
Looking at the page one lands on via the redirect trip from http://batteriser.com > http://comingsoon-tech.com/batteriser, I can't help but notice an insane amount of nearly identical wording as that which appears in the PC/MacWorld articles.
Something is quite fishy here.
---
[0]: I found this via the Batteriser Twitter account[1], which made its first tweet 12 hrs ago--declaring they've launched--with a link to the PCWorld endpoint.
[4]: someone at agency|2.0 really ought to fix the Twitter description by adding a "with" or "using" or some other such coordinating helper verb, preposition, phrase, what-have-you. one expects a bit finer fit and finish with bespoke goods. [+]
That's clever. I used a similar trick to boost the output of my windmill during low-wind days when the voltage from the alternator would not be larger than the voltage of the batteries.
I don't understand this bit:
> The next step is an Indiegogo campaign in late June, and then delivery in late September.
If they already have a working product and a price set and they're going to ship in September they should be well into mass production right now and such a campaign would not make much sense.
If made cheap enough the circuitry could possibly be internalized in the battery sleeve.
They probably need a bit of money to scale up production and do some marketing - especially the latter can be very expensive. Just look at how much advertising companies like Duracell do, for a product that hasn't significantly changed or improved in the past decade or two.
You won't get much power (Wh, as opposed to mAh) from a cell at a low state of charge. The initial lower voltage of the almost empty cell, combined with the increased voltage sag under load due to the converter pulling increased amounts of current will result in dubious amounts of actual extra energy. In any case, many complicated electronic gadgets already use some kind of voltage regulator that maximizes the runtime of the device, this gadget (if it works as advertised) would be useful only for some direct-drive lights or motors
Alkaline is still often the best choice for those really long, low draw applications. That said, if you really want NiMH, make sure it's the latest-generation "low self-discharge" ones, which do seem to be much better about holding on to power for longer. I haven't tried to put it in my smoke detector, but the low-self discharge are now reasonable for use in TV remotes and such. To be honest, unless you use your remote a lot, it's probably still more economical to use alkaline on those, but, well, my battery needs have fluctuated a lot over the years and is now trending down as the kids get out of the "battery-powered toy" phase, and the NiMH-in-hand is still cheaper than the alkaline on the store shelf, right?
I've been using low self discharge NiMH batteries for years. I find they are better than Alkaline for almost everything. They are fine in all my remotes. Last for months. It is only a couple of items that just don't work with any NiMH batteries. The smoke detector and a clock. It's not that they run dry quickly. The smoke detector fails within 24 hours (gives a battery low warning siren) and a clock that just doesn't work.
I don't mean they are bad. I mean that putting a ~5$ battery set in a remote, in a place where you're going to recharge it perhaps once or twice, can't justify the premium over just buying cheap alkalines the two or three times, max, you'll be changing batteries. (Heck, the stupid cheap ones the remotes typically ship with tend to last a couple of years themselves.) They work, and if you're in my position where you already have them, use them, but I would recommend against buying NiMH of any kind explicitly for your remotes.
The article mentions it does work for 1.2v batteries.
Except they forgot to mention that some types of rechargeable batteries get damaged if you discharge them completely.
I just wonder, if the video is part of a new, clever (or not) marketing strategy?
At least at my computer (tried with two different browsers), the video stops after 17sec or so and is interrupted in midst of a sentence by a form to enter my email address. I just wanted to view the video to the end, but have to enter my email instead??
Either an error in the page (?) or a clever marketing strategy?? In my case, not so clever, because I will not adhere to such tactics.
It could also be, that the whole thing is similar to that tactics? As jwf also pointed out, the claims are a little over the top. I don't think, that 800% are really achievable. Maybe 20-30% in real life applications. That of course could be still good, when the gadget will not be to costly and is unlimited reusable. Still the question remains, if simple rechargeable are not still better (for your economy and the environment) in cases where you have battery-intensive applications. I try to limit the usage of non-rechargeables to cases where the battery is swapped really seldom -- and in such cases, additional gadgets just make life more complicated.
As people have already discussed, voltage boosters for things like LED flashlights are already in wide use (usually called a "voltage regulator"). The tradeoff appears to be something like:
-- longer life at full rated voltage
-- when the battery dies, it dies suddenly and completely, no tapering down - one second it's on, the next second it is dead as a doornail
-- parasitic current drain drains batteries even when they're not in use
-- more expensive
They most definitely do NOT increase usable battery life by 8x.
One issue I don't see addressed is that I appreciate the warning I get as my batteries die. In an apple trackpad, like the one in the "article", I get a few weeks notice when my batteries are dying. With this am I more likely to have devices just give up suddenly?
That, plus the safety concerns and the fact that their math is bogus will probably keep me from using one.
Where are the published 3rd party test results? If all they say is true, it would be simple & cheap to get an independent test done showing a range of devices and the run times with & without the batteriser.
Their one-line statement from Dr. Kiumars Parvin is worthless on its own. Show some confirmed test results on real life items, or you are just selling snake oil.
Strange that he picked a mac keyboard for the demo. Mine works until the batteries reach 0.8v each. Batteries that are long "dead" in my kids toys make my keyboard work for weeks. (Of course the Mac starts alerting me of impending doom much sooner. Is this just a clever way to lie to the power meter and get it to shut up?)
Dumb question: do most battery meters (internal to the device) test voltage? If so, does that mean using this would give you no warning that your batteries are dying? From the demo, it sounds like they might go from 100% straight to dead, at least from the device's perspective.
No problem at all, the built-in compatibility mode will conveniently turn your rechargeables into disposables.
Jokes aside, while the technology and the "why did nobody think of this before" is certainly impressive, if this gets any market traction it will cause more landfill by hurting rechargeable adoption than it will prevent by slowing the disposable battery replacement cycle.
According to the article Roohparvar says the sleeve will also work with 1.2 volt rechargeable batteries, boosting them up to 1.5 volts., but they don't say anything about how well the rechargables would handle this usage.
The usual way for rechargables, I imagine. They'll handle it just fine until they die from an overly deep discharge.
If the chip is very clever, then it'll detect that it's working on a rechargable (from voltage curves?), and stop discharging after a certain point. But the specifics there depend on the exact chemistry used, so it'd be difficult to get it right.
Definitely yes, but (example) the rear light of my bicycle insists to be powered by two AA 1.5 V batteries. Two rechargeable ones don't have enough voltage to light it so I need disposable batteries. The front light works with 3 rechargeable ones. We should stop building stuff that needs throw away batteries.
I probably change the batteries every month or so, which is usually about 40 hours of riding. Probably too often, but whatever. The light cost $15, I think.
(Actually I'm retiring this light today and switching to a dynamo-based lighting system. No more recharging ever. Looking forward to that.)
We need this out as soon as possible. I personally think so because then we will manufacture less alkaline based batteries and save the environment. Also then things will be more efficient. We as people should protect this invention against the big company giants. Who will definitely try to kill it.
I request you all to get it out there and make the best of it.
Mr. Bob Roohparvar
I STAND BY HERE IN THIS AMAZING INVENTION'S PROGRESS
A good boost converter will be ~90% efficient (it can be more efficient, but not miniaturized like the pictures show). So, to begin with, you'll discard ~10% of your energy.
Now look at AA alkaline discharge curves: http://www.powerstream.com/AA-tests.htm
Indeed if you gadget reports the batteries as dead at 1.25V, you can still get ~40% more usage. But most gadgets don't work that way. 1.25V is the normal voltage of a fully charged NiMH rechargeable AA, so if you gadget works with those, the real cutoff point is likely closer to 1.15V or so.
The booster will boost the voltage (at the expense of current, obviously, plus losses) so that even though the battery will be below 1.15V, output voltage will be at 1.5V. Looking at the graphs, this buys you less than 1/5th, and if you consider the losses in the boost converter, probably half that.
The "800%" claim seems totally bogus. Perhaps with a gadget that stops working when the voltage falls below 1.45V per cell.
I'm not saying it's not a useful gadget (and I'm very impressed by the miniaturization: where is the inductor? This thing must run at several MHz at least!) — just that the claims should be taken with a large grain of salt.