Getting power from a USB powerbank

Discussion in 'Electronics & Electrics' started by RobRoySyd, Nov 15, 2019.

  1. RobRoySyd

    RobRoySyd Member

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    I now have quite the collection of USB power banks from the small to large capacity and am having an issue using them to power a cheap Ikea single LED light. The lower capacity power banks happily power the light for many hours i.e. until they're clearly out of charge.
    My problem is the bigger ones refuse to power the same light for more than a minute. I've tested these and they are capable of delivering close to their rated capacity to other loads. My question is what's different about the Ikea light that causes the bigger power banks to turn off the power after around 1 minute. According to my USB power meter the Ikea light draws less than 10mA.

    My research suggested I may need to connect pins 2 and 3 of their USB outputs to convince them to play along but that hasn't worked. It seems these power banks don't like very light loads which may make some sense if their only function is to charge other devices.
     
  2. aXis

    aXis Member

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    Some of the powerbanks have auto power-off, so if the load is light they will go into standby.

    As crumby as it sounds you may have to increase the load. Possibly a small arduino could be programmed to pull a higher current periodically to keep it alive, without wasting too much power.
     
  3. merlin13

    merlin13 Member

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    What light? You've got me curious about all this...

    Quick tickle of Uncle Google also shows a few hits showing fiddling the impedances 'tween all of the USB pins on the device being powered, to show the charging device the expected/desired charging power required. Maybe your bigger power banks are somewhat "intelligent" per se perhaps and just too damned smart for their own good to run a a dumb LED?

    And a few hits also indicating a 200 ohm resistor across the data pins on the light. Worth a shot of some ohms instead of a dead short?

    eg, out of the Power section of the Wiki page on USB (https://en.wikipedia.org/wiki/USB#Power) there's a bit saying "...To recognize Battery Charging, a dedicated charging port places a resistance not exceeding 200 Ω across the D+ and D− terminals.[81]...""

    Depends on how the 'bank detects handling the increased load and how it determines it needs to drop into standby (load current thresholds, hysteresis/timing thingy...).

    And an Arduino might be a bit of an overkill perhaps - personally either a 555 (KISS Principle) or even a small resistor (serious KISS Principle), assuming the wasted power won't be ridiculous.

    Or perhaps better yet, Frankenstein that LED light and fit more/bigger LED(s) into it? Might as well use the "wasted" power for good...
     
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  4. OP
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    RobRoySyd

    RobRoySyd Member

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    It's the JANSJÖ.



    The spec actually says not more than 200 ohms.


    What's interesting is three quite different powerbanks behave exactly the same but then again there's only so many was to design them. Of course it makes sense if all the powerbank is meant to do is charge a phone. A low current load is obviously not a phone charging its battery so better to stop powering the load. In fact I'be noticed this sort of behaviour when charging a phone from a powerbank. The phone battery can be charged just fine but then the powerbank stops delivering power and one of the powerbanks documentation does say you cannot use it to power the phone...only charge the phone

    Yes a 555 should be all it takes but I was hoping to keep it really, really simple otherwise the whole purpose of the light + powerbank is kind of lost.

    Thing is the small 1,000mAH units will run the Ikeas light for several nights. I have a much brighter USB LED light that'll run forever off the bigger powerbanks but it's way more light than needed and the runtime works out about the same as the smaller light on the smaller powerbank
     
  5. merlin13

    merlin13 Member

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    ...which looks suspiciously like the 3 watt COB LED bedside lamp I've got here that runs off an integrated 7 volt wall wart.

    But yours is only 10 lumens, which means it has to be either not be a 3 watt COB chip, a seriously-limited 3 watt chip or simply an LED or two - if you look down the barrel what's in the business end of it?

    Ain't going to get much simpler than Ye Goode Olde 555, unless you go back to actual transistors... :)

    Okay then, let's try this train of thought - at least for your super-bright LEDs how would a PWM circuit sitting on the output of your large powerbank(s) go perhaps, to adjust the light output?

    Ye Goode Olde 555 will run off 5 volts and can handle 200mA continuous Sink/Source (fiddle the PWM average to not exceed that), set it up in Astable Mode and fiddle it to give you the low light you want.

    All assuming the powerbanks wouldn't get all bitter 'n twisted on a PWM load of course...

    Real Olde Schoole would be ditch the powerbanks, acquire a serious 18650 or two with associated charging 'n output stepdown/stepup circuits and slap together a dedicated powerpack for that particular LED. I might even have enough of all the bits laying around here somewhere if you offer a decent-enough bribe... :)

    Or just deem this All Too Much Dicking About and go back to using candles... :D
     
    Last edited: Nov 24, 2019
  6. OP
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    RobRoySyd

    RobRoySyd Member

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    It's a single yellow square. Current consumption is less than 10mA. At a guess 1W LED.


    Might give this a go as I have a few LED PWM dimmers lying around.

    Already have a rechargeable LED light with 18650 inside it but China has run out of them. I don't get why the Chinese don't make more as they sold out very quickly.

    As for candles well I have plenty and quite a few vintage kerosene lamps. Those lamps are very Australian as the glass bottoms are repurposed Vegemite jars. Given the vintage the wicks are probably asbestos :(
     
  7. merlin13

    merlin13 Member

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    Yup, COB and prob a 1 watter then. Albeit my 1 watt COBs still put out a hellava lot of light, enough to use a couple for workbench illumination unfocused when I don't need surgical suite light levels...

    So do I, both the little heatshrunk inliners and The Box With The Knob. But mine won't run down at 5 volts input...
    Okay, but isn't the whole point of this diatribe to get your JANSJÖ running off of your beefy powerbanks?

    Because the next Obligatory Dumb Question is, what are you trying to light up/do with your JANSJÖ? That's basically a low-level laptop keyboard light.
     
  8. OP
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    RobRoySyd

    RobRoySyd Member

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    Yes the point is to get the JANSJÖ running off a large powerbank however that's sort of part of a larger project.
    The purpose of the larger project is providing light both indoor and outdoor on a remote island using readily available units.
    USB Power banks are commonplace and there's now a variety of things that'll run off USB power. Maybe I just need to provide an additional unit to fool the USB power banks into giving up their joules regardless of what's plugged into them.


    Amusing anecdote:
    As hinted at, candles were tried indoors but then helium filled balloons were added to the decorations and said balloons were tethered to the dining tables via inflammable ribbons. A slight breeze put a ribbon over a candle and then there's something on fire heading towards the high ceiling. Eventually the fire reaches the balloon, it burst and the burning plastic falls downs.
     
  9. merlin13

    merlin13 Member

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    Let us know if the PWM thing works. Or go through the pain of finding bog-stock low-level USB light and powerbank combinations that work.

    Else bite the pillow/bullet and go home-rolled, with the added advantage there of adding additional bits like daylight sensing auto On/Off etc and even making them waterproof for the remote island use - you're not looking at commercial quantities for them, are you?

    Oh, and if you haven't already got one, for what you're jousting with there something like one of these might be handy... :)
     
    Last edited: Nov 26, 2019
  10. OP
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    RobRoySyd

    RobRoySyd Member

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    I have combinations that work but they're all 1000 mAH or less. They're a tad too small physically as well. The bigger units I can affix to many things just using industrial Velcro, that is quite expensive but it's 100% Nylon and man alive, it really does grip.

    Don't really need dusk sensing as they'll be setup for the event and then taken down. Quantity is that nasty area of around 50 which is a PIA to build oneself and not enough to get the CCP interested....Then again if there was a market for such things. Regardless I would prefer something that I don't really have to support too much. There's other options such as motorcycle SLA batteries and 12V lights of some form but just not as neat and compact.

    I do have a USB power meter but not that fancy, might upgrade anyway. Thanks for your input.
     
  11. koss

    koss Member

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    What I use is a 20v power tool brick from Aldi and one of these little boards.
    https://www.ebay.com.au/itm/FT-KE-6...-Buck-Volt-Step-down-Converter-S/323963626516

    I plug it into the Aldi power tool brick using one of those old fashion Telstra cream telephone wall plugs, and it will run with no load attached whatsoever. It's got about 60Wh of storage, maybe more, depends on the power tool brick you use.
     
  12. merlin13

    merlin13 Member

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    So depending on the budget and the timescale when you need them, farm the hardware side of it out... and koss is already showing the hard part of it Done Dirt Cheap.

    As far as a market for such, quite likely there's already "things" somewhere on the planet that would pretty well do what you want, but Silly $$.

    And if there isn't and you delve into making enough fro resale elsewhere it wouldn't take long for "someone" on the other side of the planet to start making 'n selling them at 1/10 your best price, driving you into bankruptcy.

    But overall something like that for a short run of 50? If I wasn't full-time Carer for the Missus I'd take it on purely out of boredom...
     
  13. v81

    v81 Member

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    Some powerbanks will cutout if little current is being drawn (as we've heard).
    Some however have an over ride for this, with Xaiomi i think you just hold the power / status button for a second or 2 and it stays on regardless.
    If you have any docs or buttons you could try this?
     
  14. OP
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    RobRoySyd

    RobRoySyd Member

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    Holding the "power check" button for two seconds didn't help. :(
    Downloading the user manual did :)
    https://i01.appmifile.com/webfile/g...Power_Bank_2S.pdf/"10000mAh Mi Power Bank 2S"

    As yet haven't tried this with the other power banks but I strongly suspect they'll be the same.
    Note to self; need to stop watching so many AVE videos.
     
  15. v81

    v81 Member

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    I'd suggest sticking with it.
    The fine genital man is quite clever.
    He even added powerbank functionality to his wife's hoo hah rattler.
    Keep yer dick in a vice!
     
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  16. OP
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    RobRoySyd

    RobRoySyd Member

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    Unfortunately the "low current discharge mode" is not answer to the maiden's prayers I had hoped it would be. After several hours of powering the light the power bank still shuts down. I don't have a precise measurement of the time but it's more than 4 hours and less than 10.
    That's probably going to be enough for dusk to midnight applications but not enough for an indoor night light.
     
  17. v81

    v81 Member

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    Bugger.. sorry to hear.
    Other option is to find a powerbank that some how really does stay on.
    If you know which end of a soldering iron is the hot one you could DIY something.

    1 x USB -> lithium charger board (example 1 -- example 2 -- example 3)

    1 x Lithium (nominal 3.7v) to USB (~5.0 - 5.2v) boost regulator (with over discharge protection if not included with the battery and no other smarts that will shut it off) (my shitty e-bay fu search only came up with 1 option that had a type a already on it).

    (Possibly both of the above in 1 unit?) (This one doesn't seem to have a type A female out, but you might make it work)

    1 x Lithium battery (integrated basic protection would be wise, over current/under voltage) - anything that is single cell, I'd suggest minimum 2amp hour, be very very weary of untrusted sources. (or steal them from an existing power bank)
    I stick to Master Instruments for lithium batteries where i can, costs more, but getting know quality is worth it (don't think they deal with public).
    Most battery zone type places can order in, some even have protected 18650 cells in stock.

    Tie it all together and Robert's your mothers brother.
     
  18. OP
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    RobRoySyd

    RobRoySyd Member

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    Already have low capacity power banks that do stay on. Purchased from Officeworks for a pittance. One (no name) has a 18650 cell inside it, the other (Comsol) is so thin it has to be LiPoly. Both only turn their output off to prevent the cell voltage dropping too low to be safe.
     

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