back to article Oh Mi: Xiaomi shows off 80W wireless charging, claims battery fully fat again in under 20 minutes

Xiaomi has demoed its latest 80W wireless charging technology that it claims can fully replenish a 4000mAh smartphone battery in 19 minutes. The tech — dubbed, somewhat predictably, Mi Wireless Charging — is not yet available on a commercial device, although Xiaomi showed it in action on a modified Mi 10 Pro. Wireless …

  1. Dwarf


    Can someone please train marketing people about SI units and how they work.

    Its a 4AH battery, not 4,000mAH nor 4,000,000uAH or 4,000,000,000 nAH.

    OK, technically they are all identical, but the whole purpose of using the correct units is to make things easier to understand, not to try and over-inflate a specification.

    Imagine if this idea were to take on in areas such as house buying - they specify the house in square millimetres rather than square metres for example.


    This has given me a slight chuckle though, as it reminds me of a lab setup I saw early in my career that had a large sign showing "DANGER, 12,000mV" to stop people fiddling with it.

    1. Anonymous Coward
      Anonymous Coward

      Over the pond they use square feet for floorspace and lie about it in New York.

      1. jake Silver badge

        To be fair ...

        Everything to do with housing is lied about in New York. It's worse in Joisey. And worse yet in DC ... The US would be a lot better off without everything east of the Great Appalachian Valley.

        1. Snake Silver badge

          Re: To be fair ...

          "The US would be a lot better off without everything east of the Great Appalachian Valley."

          If you don't mind what would be left of the U.S. to slip into being a second-rate power, considering that once you subtract California and Chicago almost all the big U.S. financial business happens there.

          Sounds like the dreams of the Civil War separatists. Again.

    2. Prst. V.Jeltz Silver badge


      i translated that to 4AH ,

      and then thought : smartphones have that?

      i have dewalt tools with 4ah batteries and they are the size of 5 smartphones!

      1. Neil Barnes Silver badge

        Yabbut... I might suggest that the power tools have batteries with multiple cells in series to achieve a higher voltage - 3 ~= 10v, 6~=20v and so on, while the mobile phone is just a single cell at 3.4v or so.

        Amp-hour rating doesn't consider voltage; but for more volts at the same Ah you need more volume.

        (or possibly parallel-series combinations, as often seen in electric vehicles).

    3. seven of five

      Nice. Reminds me of our "Caution, NITROGEN rich atmosphere inside." sign on the datacentre door.

      1. jake Silver badge

        My publicly accessible greenhouses have prominent black on yellow CAUTION! DiHydrogen Monoxide spraying inside! Proceed at own risk! ... Keeps the know-it-all greens picking up their CSA packages from poking their noses in and making a mess of things.

    4. Prst. V.Jeltz Silver badge

      they specify the house in square millimetres

      I wouldnt mind that if they actually included all the measurements,

      but they never give you the size of the plot, garage or gardens !

      which is all i'm interested in

    5. Dr_N

      Ampere Hours are not an SI Unit. Just sayin'.

      1. Ochib

        One ampere hour equals 3600 C, hence 1 mA⋅h = 3.6 C.

      2. DavCrav

        "Ampere Hours are not an SI Unit. Just sayin'."

        14.4 kAs?

      3. jake Silver badge

        "Ampere Hours are not an SI Unit."

        Neither are any of the units on a Web page, but you use the Web without complaint, and understand what you are looking at, right? So what's to bitch about?

        1. Dr_N

          OP suggesting people needing schooling in the use of SI units when they aren't SI units?

          1. Dwarf

            OP (that will be me) was talking about standard SI prefixes as defined here NIST Metric SI Prefixes, so I take a prefix as part of the broader SI standard. I think that the AH bit stayed constant through the discussion and that wasn't in question as batteries are specified in this manner.

            So, which of us needs schooling - other than probably all of us since we can all learn a new trick now and then. :-)

            I'm reflecting more on the Pres V.Jeltz posting as I'd never considered the battery size impact against power tools, unless that just marketing fresh air and a tiny little battery in the middle to make it look the part and some concrete to make it feel the part too.

            1. Dr_N

              Well if you'd said "Unit Prefixes" in the 1st place ...

              Just out of interest, should it be 0.25um or 250nm ?

              1. Cynic_999

                "Just out of interest, should it be 0.25um or 250nm ?"

                As with any other choice of units, it depends on the context. Look at all the measurements used in the context, and see whether they could all be expressed sensibly using a single base prefix. If I were discussing bacteria that range in size from 500nm to 0.7mm for example I would probably use um as the best compromise (thus 0.5um to 700um) as opposed to describing one bacteria as being 500nm in size and another as being 700um - which at a glance may give the impression that the latter is only slightly bigger than the former instead of being more akin to the difference between an ant and an elephant.

              2. Dwarf


                Yep, I like that. :-)

                I'd argue that 250nm would make most sense as its less likely that someone would miss the decimal place, but if it was a mile, we say half a mile or half a metre, so I guess it depends on context and that's what the standards allow for - flexibility to use the most appropriate term for the situation.

                Anyhow, its time for 0.568L of beer now, so cheers !.

                1. Dr_N
    6. The Oncoming Scorn Silver badge

      Maximum Power

      I seem to recall that the model railways at Pecorama (Beer East Devon) at least in the 80's, used a similar signage as indication of extreme volts to stop people reaching in to fiddle with the layouts.

      Icon - Because of Beers infamous smuggler.

    7. Anonymous Coward
      Anonymous Coward

      Its a 4AH battery, not 4,000mAH nor 4,000,000uAH or 4,000,000,000 nAH.

      OK, technically they are all identical

      Not quite, because they differ in precision, which is defined as +/- 1 of the last digit.

      This is why 400W is only equal to 400.00W from a mathematical perspective, but not as a measurement. The first is 400W +/1W (so somewhere between 399 and 401W), whereas the second is 400W +/1 0.01W (so somewhere between 399.99W and 400.01W).

      Pedantic as this is, it's 99.99% certain that I screwed up describing this :).

      1. Cynic_999


        This is why 400W is only equal to 400.00W from a mathematical perspective, but not as a measurement. The first is 400W +/1W (so somewhere between 399 and 401W)


        Not what I was taught.

        IIUC 400W would imply somewhere between 350W and 450W Trailing zeros (if there is no decimal point) are not significant digits, but just place-holders, and implied precision is up to +/- half the place value of the least significant digit. In this case the least significant digit is "4" with a place value of 100, so the implied precision is +/- 50W

        420W implies somewhere between 415W and 425W, while 421W implies between 420.5W to 421.5W

        If someone said that they paid around £400 for their new washing machine, you would probably not assume that it cost exactly £400, nor that it cost between £399 and £401. But thinking that it cost somewhere between £350 and £450 would be a more reasonable assumption.

        Tough if the value you want to give happens to be a "round number" with a higher precision than the number would imply. In that case you should explicitly give the precision, accuracy, tolerance, error margin etc.

        1. jake Silver badge

          "400W would imply somewhere between 350W and 450W"

          No, 400W means it'll deliver at least 400W. On more reputable units, it'll usually have some undefined fudge factor over that to cover minor corrosion, dust, fingerprints, dog spit, toddler drool and the like on connectors. Cheap-assed chinesium variations don't always come with the built-in fudge factor, thus burning "hoverboards" & other tat.

          Caveat emptor, quia ignorare non debuit quod jus alienum emit.

      2. anthonyhegedus Silver badge

        On they sell 12,000,000 mAH batteries the size of a pack of cards.

        1. Anonymous Coward
          Anonymous Coward

          That's just wish-ful thinking..

    8. Cynic_999

      I disagree. It does not matter what units you use, but whatever you decide on should be used consistently. Just as one room should not have its dimensions given as "400cm X 1200cm" and another room described as "5m X 7m", you should not label one battery "3000mAh" and another "4AH" It makes it easier to compare. Small batteries (rechargeable or not) have until recently only been available in capacities near or below 1Ah, and so were always described in terms of mAh. Until capacities above 10Ah become comonplace, I see no harm in continuing that method

      1. Charles 9

        Point taken. If you maintain your own UPS units you will find the sealed batteries that back them up are typically rated in the AHs (@ 12V) because the smallest ones available today are around 5AH (and they haven't really had to produce one below 1AH for quite some time). It's one reason Americans stick to their units: they're so used to them at this point (and there are so many of them) that attempting any significant metrification is going to be less a project and more an operation.

    9. Screwed

      I am often involved in discussing medicine doses and the things that cause much confusion are switching between units and using decimal points - rather than (generally) whole numbers.

      For example, vitamin B12. Required daily amount for many of us is around 3 micrograms. Standard low oral doses are 50 or 100 micrograms. Common high oral doses are 1,000 and 5,000 micrograms. Common injectable dose is 1,000 micrograms.

      It just engenders confusion if the unit is switched to milligrams for doses of 1,000 micrograms and higher. Even more so when see 0.1 or 0.05 mg.

      For batteries, we do see capacities below 1 Ah - such as some AAA cells. It is simpler to continue using mAh for all smaller batteries. Only going up to Ah when there would be no interest in anything after the decimal point.

  2. Antron Argaiv Silver badge


    Hmmm...horrendously inefficient, full charge in 20 minutes, lots of heat, LiIon battery, cellphone, Quality Chinese Engineering.

    I don't want to be a killjoy here, but IF I were planning to use this to charge my cellphone, I think I might try it out on a large concrete pad, far away from anything flammable. I fear a repeat of the "hoverboard problem" of a few years back.

    1. spold Silver badge

      Re: Hot as well as charging your phone during lunch, you can toast your lunch while charging your phone. Double win?

  3. Prst. V.Jeltz Silver badge

    Vivo was able to adopt a unibody design, with the chassis enveloped in an unbroken sheath of glass. Apple has reportedly considered using this form-factor, too.

    I see , make the hundreds of £s worth of phone unrepairable . thanks.

    1. DavCrav

      "I see , make the hundreds of £s worth of phone unrepairable . thanks."

      No, it's completely repairable.

      1) Break the glass case.

      2) Make repair.

      3) Plunge into molten glass to reform new case around the phone.


    2. jake Silver badge

      In case of emergency, break glass!


  4. Prst. V.Jeltz Silver badge

    But let's not herald the advent of a totally cord-free future just yet: wireless charging is horrendously inefficient when compared to standard cabled charging,

    Totally fucking pointless white elephant gimmick.


  5. Prst. V.Jeltz Silver badge

    decided to pre-empt any action, with Apple removing the charger and headphones from the latest iphone

    Thereby making sure extra shipping and packaging is required.


    the opposite of the intended outcome

    1. Anonymous Coward
      Anonymous Coward

      I think the point was that people neither need or use these items once they or on the nth ‘upgrade’ cycle. My iPhone X came with both power and headphone / lightning adaptors which are still bnib for when I resell.

      1. jake Silver badge

        "people neither need or use these items once they or on the nth ‘upgrade’ cycle."

        MeDearOldMum (and other technologically incompetent people I know) refuse to plug their kit into anything that didn't come with that kit out of fear of breaking it. A phone that doesn't come with a charger is not a phone that they will purchase, period.

        1. Anonymous Coward
          Anonymous Coward

          OK, but she stems from that era where Nokia and others managed to make phones with identical power plugs but with wildly different voltages coming out of the adaptors between brands - in those days that was a very sensible approach.

          But, as in the wet monkeys and ladder under a banana experiment, the original cause for this has gone as the quickchargers that DO push out more than 5V like QC2 and QC3 first try to have quiet chat with the receiving end if it can handle it - if no confirmation is forthcoming, 5V it is.

  6. This post has been deleted by its author

  7. Graham Cunningham

    S.I. units


    Just saying. ;)

    1. jake Silver badge

      Re: S.I. units

      Because you don't know what an AH is? What ARE they teaching you lot in countries infected with the mandatory metricals, anyway?

      1. Anonymous Coward
        Anonymous Coward

        Re: S.I. units

        An "AH" is the expression uttered after finishing a core dump of a more physical nature. Depending on the final amount of weight loss or difficulty getting the process started, more "H"s may be used, i.e "AHHHHH".

        Any other questions?

  8. Anonymous Coward
    Anonymous Coward

    Hmmm wireless charging, let's waste a few more GWhs of electricity through poor efficiency thanks to those being too lazy to plug their phone in.

    When we've mastered limitless energy like the Krell from the Forbidden Planet then can we be willy nilly with our telekinetic energy demands but our National Grids can barely keep up so think efficiency folks and avoid load shedding.

    1. jake Silver badge


      The green & granola crowd have something real to gripe about. Will wonders never cease.

      1. ICL1900-G3

        Re: Finally.

        Have you got a spare planet somewhere you're not telling us about, or do you just not care?

    2. DS999 Silver badge

      Who cares about efficiency for phone charging?

      A phone with a 4000 MaH battery stores requires about 0.011 KWh to charge from flat. If you had to charge it from flat every day you'd use a grand total of 4 KWh in a year. The average person uses quite a bit more than that in their house every day, let alone the energy impact of all their other activities.

      I think wireless charging is stupid and pointless, but not because of efficiency. If you want to reduce your carbon footprint, install solar panels, replace your AC with a heat pump (or geothermal heat pump in a climate that has a real winter, unlike most of the UK) get a car that uses less gas, etc. Worrying about rounding errors is dumb when there are so many far larger targets that most people have. Only those who have already taken all those measures should be worrying about the efficiency loss of wirelessly charging their phone.

  9. IGotOut Silver badge


    There’s an inevitable environmental cost to producing a USB-C cable: from obtaining the raw materials, to transporting them, to manufacturing the cable, and finally, to shipping the product to retailers""

    So wireless chargers don't need any of those?


    1. TonyJ Silver badge

      Re: Wtf?

      "...So wireless chargers don't need any of those?..."

      I was going to say exactly this!

      "... have dewalt tools with 4ah batteries and they are the size of 5 smartphones!..."

      I have a DeWalt drill in front of me right now that takes 5Ah batteries and they are big (around 120 x 70 x 70mm) and heavy.

      1. Blane Bramble

        Re: Wtf?

        Your DeWalt 5Ah battery is probably 18v not 3v or 5v though.

        1. jake Silver badge

          Re: Wtf?

          It would be trivially easy for DeWilt to convert that same 5AH battery over to 3 or 5 volts (or both!). Hopefully they'd have the wit to change the connector, but with DeWilt I wouldn't hold my breath ...

  10. mark l 2 Silver badge

    There are other impracticality to wireless over wired charging other than the extra power it takes. At current I can charge my phone while using it for GPS navigation or playing music from a dock in my car using a USB cable something I couldn't do if it was wireless charging. And even when charging at home I can hold the phone at whatever distance my USB cable length is from the charger (about 1.5 metres for my setup) and continue to use it while its charging rather than having to leave it on a charging pad until its charged up.

    So I for one would not buy a phone that removed the wired charging option for a totally wireless charging solution

    1. Matt_payne666

      I can charge my phone wirelessly in the car holder, with the display on max, while using navigation and streaming spotify over 4G via bluetooth to the cars entertainment...

      and thats an ageing Galaxy S7edge... its not charging fast, mind and it does get rather toasty!

  11. JDPower Bronze badge

    Excellent, now phone companies can use even smaller batteries.

  12. Henry Wertz 1 Gold badge

    Replace battery much?

    Replace battery much?

    In case you aren't aware, without some kind of new battery technology, fast charging batteries is BAD for them and drastically cuts battery life! You charge your notebook battery over 4 hours or so.. I had a Gateway that did that, 8 year old battery had 92% of the capacity it had new. The typical 1-1.5 hours to charge from flat, that battery hits 90% capacity within a year or two and is between "totally dead" and maybe 50% capacity after 5 years. 20 minute charging? Expect to replace that battery every year.

    I'd actually like the opposite -- an option on my computer and phone to tell them "it's going to be plugged in all night, take 6-8 hours to charge and preserve the battery please." I guess a few of the Lenovos have an option like that -- normal charge, slow charge, and a fast charge (which if I recall had some tattler built in so it'd void the battery warranty either after 1 or a few uses.)

    1. Charles 9

      Re: Replace battery much?

      "I'd actually like the opposite -- an option on my computer and phone to tell them "it's going to be plugged in all night, take 6-8 hours to charge and preserve the battery please." I guess a few of the Lenovos have an option like that -- normal charge, slow charge, and a fast charge (which if I recall had some tattler built in so it'd void the battery warranty either after 1 or a few uses.)"

      Many phones I know with the ability give you the option to turn off fast charging. There's also the option of physically hooking the phone cable to a limited-current charger (like a 1A output).

  13. Pascal Monett Silver badge

    Kill wireless charging, please

    I don't care that the hipsters find it cool. Wireless charging is just one more drop in the ocean of problems that is climate change.

    Never have we found a worse way to waste electricity for the sake of convenience. Get your ass off the couch and plug that sucker in. You have limbs, you need the exercise.

    1. jake Silver badge

      Re: Kill wireless charging, please

      Or don't get your useless, fat ass off the couch and get a sofa with a USB port built in ... think of all the energy you'll save!

  14. Patched Out

    Capacitance Units

    In reference to SI prefixes: As an interesting aside - for some reason, U.S. electrical engineers have traditionally not used the "nanoFarad" as a unit of measurement for capacitance. The common units are microFarads and picoFarads. So it is not uncommon to see a 1,000 pF capacitor next to a 0.01uF capacitor on a schematic. I'm wondering if it is because a sloppily written u could look like an n or vice versa (back when most schematics were hand drawn).

  15. _Matty

    SI Units

    A current multiplied by a time (mAh) is a measurement of electric charge; its SI unit is the Coulomb (C)

    To calculate the amount of energy a battery can store, one has to multiply this "marketing" figure by the voltage the battery operates at. The SI unit for energy is the Joule (J) although kJ would probably be better for consumer electronics. The advantage of using the correct units is that it enables easy comparison of the energy stored in your smartphone with the energy available from the snacks you're consuming while scrolling.

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