Teardown: LED Bulb Yields Tiny UPS

Occasionally you run across a product that you just know is simply too good to be true. You might not know why, but you’ve got a hunch that what the bombastic phrasing on the package is telling you just doesn’t quite align with reality. That’s the feeling I got recently when I spotted the “LED intellibulb Battery Backup” bulb by Feit Electric. For around $12 USD at Home Depot, the box promises the purchaser will “Never be in the dark again”, and that the bulb will continue to work normally for up to 3.5 hours when the power is out. If I could repurpose that to make a tiny UPS for a microcontroller project of my own, it could be even more useful.

Now an LED light bulb with a battery in the base isn’t exactly rocket science, we can understand the product conceptually at a glance. But as they say, the devil is in the details. The box claims the bulb consumes 8.5 watts, but a battery with enough capacity to run such a load for 3.5 hours would be far too large to fit inside of a light bulb. Obviously there’s more to the story.

On the side of the box, in the smallest font used on the whole package, we get our clue. The bulb drops down to 200 lumens when in battery backup mode, or roughly as bright as a cheap LED flashlight. Now things are starting to come together. Without even opening the device, we can be fairly sure it will contain two separate arrays of LEDs: one low set for battery, and a brighter set to run when the bulb has AC power.

Still, I tend to be of the opinion that anything less than $20 or so is worth cracking open to see what makes it tick. Even if the product itself is underwhelming, there’s a chance the internal components could be useful or interesting. With that in mind, let’s see what’s inside a battery backup light bulb, and what we might be able to do with it.


I fully expected to have to cut the bulb open, but was pleasantly surprised you can disassemble it non-destructively. Not that it was the intent during manufacturing, of course, but it’s a nice side effect of the fact that some poor soul probably had to assemble these things by hand.

If you squeeze the frosted plastic dome, eventually the glue used to secure it will pop, and from there it just takes some light prying to release. Once the dome is off, you’ll be presented with the LED array. Three screws around the outside of the LEDs will allow you to pull all the electronics out of the bulb. Two wires run down into the base, which unfortunately appears to be pressed into the plastic permanently. So to extract the electronics you either need to snip the wires or desolder them from the board.

LED Array

As expected, there are two concentric rings of LEDs in the array which turn on or off depending on whether the bulb is on AC or DC power. The inner ring of LEDs as well as the five in the center light up when on DC power, and when AC is available the outer LEDs come on. It’s worth noting that the center LEDs don’t get any brighter on AC versus DC, but that the outer LEDs are much brighter than the inner.

This makes sense given the information on the box: if the total output of the bulb is 600 lumens, but only 200 lumens on battery power, we know that the outer LED ring must output roughly 400 lumens on its own.

The array looks reasonably well made, and is attached to a rather nice circular aluminum heatsink. While the wires aren’t labeled, it isn’t hard to figure out that the center wire is negative and the two outer wires correspond to the two LED rings. This module would be very easy to reuse in a project where you might want variable brightness without having to bother with PWM.

Power Supply

The board should look pretty familiar if you’ve ever seen the inside of an LED bulb before. It’s a double-sided PCB with a fairly simple layout: transformer and capacitors on the top side for AC to DC conversion, with the flip side featuring the brains of the operation. The white connector on the top side of the board connects to the 3.7V 2000mAh battery, which incidentally takes up most of the internal volume of the bulb.

Theory of Operation

The thing to remember about this bulb is that it isn’t like an emergency light; it doesn’t just automatically turn on when the power is cut. It’s a light bulb, after all, and it needs to turn off when you flip the switch or unscrew it.

Instead the bulb detects when power is lost in the circuit it’s connected to. It does this by testing the resistance between its AC terminals when it loses power. If there is “infinite” resistance, it knows that it has been switched off or unplugged.

Interestingly, the circuitry in the bulb is sensitive enough that if you hold the bulb in your bare hand it will see it as an unpowered circuit and light up. Depending on your sense of humor, that might be worth the $12 alone.

I wanted to clarify how the bulb works, because I think it opens up some interesting possibilities for reusing the hardware. If the LEDs operate at 3 V, and the bulb’s circuitry is able to maintain that voltage no matter if it’s connected to AC power or not, we essentially have a low voltage uninterruptible power supply (UPS) on our hands.

Proof of Concept

The power is probably pretty “dirty”, and spikes when coming on and off of AC seem likely. You should have a big capacitor across the DC side of this board at the very least. But as a quick demonstration, I was able to take the LED wires and stick them right into the 3.3 V side of a Wemos D1. Again, this isn’t a great idea, but shows the basic premise is workable.

If we assume a consumption of 250 mA for the D1, this little hacked UPS should be able to run it for at least 5 hours or so. Given the advertised 3.5 hour run time figure, as well as the 2000 mAh capacity printed on the battery, this board should be able to supply at least 400 mA at 3 V. With a boost converter you could get 5 V out of it, but probably not with enough current to run much.

A lot of people are hesitant to fiddle with AC circuitry, so the fact that this offers a turn-key solution and lets you focus on the DC side is a big plus. With the addition of an enclosure and lamp cord for the AC side, this could be an interesting “Poor Man’s UPS” for microcontroller projects constructed entirely from parts available at Home Depot. There’s a certain MacGyver element to being able to set something like this up without having to leave your local big box store.

Worth It?

There’s some decent hardware in the bulb that might be worth the cost of admission, especially when these bulbs invariably hit the clearance section for $6 or so. The dual-brightness LED array and relatively beefy battery can be easily repurposed, for a start. It’s not the best salvage deal we’ve seen from the Home Depot, but you could do worse.

But personally the idea of using these bulbs as a cheap DC UPS is the most appealing to me. It certainly warrants further investigation, and it would be interesting to see what the community can come up with in terms of appropriate loads to swap the LED array out for. I’ll be doing some more work with this concept, so keep an eye out for a future post on the subject.

90 thoughts on “Teardown: LED Bulb Yields Tiny UPS

        1. When the power is out and the bulb is turned on, the bulb is directly in parallel with the output winding of the step-down transformer for the house, which is close to zero ohms. Snubber circuits are not only a lot more resistance, but usually resistance in series with a capacitor. The key is that the test is done with DC.

          The more difficult case is where a device is plugged into the same switched circuit, that has a transformer input, since again you’re measuring a very low resistance, even if the wall switch is turned off.

      1. Yes, that’s what it means. I’ll tell you, if I didn’t know about these, it would freak me out if ONE light in my house worked when I flipped the switch. Even worse if two or three of them were working. I would be saying things to myself like, “did a power surge knock out every appliance except a couple of LED bulbs???? And then I’d get out the voltmeter.

  1. “On the side of the box, in the smallest font used on the whole package, we get our clue. ”

    One of the more annoying things about marketing.

    “But personally the idea of using these bulbs as a cheap DC UPS is the most appealing to me.”

    I imagine in a world where resistive lighting was king, just things might not have come about. All hail the mighty LED.

      1. That’s what she said! /s

        $12 isn’t really that great a price for a battery, so if you don’t know who Uncle Fester is then I question if you’re going to have any use for this other than as a emergency backup light.

    1. Oh, it’s almost certainly using lithium batteries. “3.7V 2000mAh”? Check. And the ‘803040-2p’ marking leads me to believe that it contains two “803040” pouch cells, which are advertised as 1000mAh each.

          1. The battery might not combust, but it sure as heck won’t work as a backup light after some months, because storing a lithium cell charged up in a high temperature environment destroys it in a short order.

            It can get to 85 C in those LED bulbs, and usually the electrolytic capacitors pop first.

          2. One concern is if they are leaving the battery fully charged (4.2V) all the time, the battery will eventually swell up which could cause physical damage or risk colliding/shorting with the PCB. Being at high temp most of the time will exacerbate the issue.

          3. i’m not sure some people understand how cool these (and similar) bulbs run. it’s not uncommon for these to operate at less than 95°F (35°C) temperature, that is to say they generate less heat than imagined here. old LED bulbs are wicked heaters surely; these are not. and many now have no heatsink attached to the aluminum PCB of the LED’s.

          4. >”i’m not sure some people understand how cool these (and similar) bulbs run.”

            They haven’t broken the laws of physics yet. If it’s really 8.5 Watts, it’s going to put about 6.5 W of that into the enclosure, and it does get hot.

        1. Lighting has exceptions for most of the tests. In many cases, all that would get tested to get the stamp would be, “Yep! This is only designed for lighting!”

          People are often confused by safety testing generally, though; even people who work with it. A couple weeks ago I had an electrician insisting that if it is a UL approved light socket then I shouldn’t have to worry about captured heat; he had no concept of the difference between testing the safety of the device and testing the safety of an application; he just didn’t want to believe that everything could be up to code, and also properly safety tested, and yet there could still be a fire hazard from placing too high a wattage bulb in the socket. (In this case, anything over 8W retains excess heat) The safety codes also don’t care if a product is electronic and would fail from heat buildup if operated continuously, they only care about if it bursts into flames. It doesn’t burst into flames, it just overheats and lights die too fast.

          The funny part is that people who are generally against safety regulations and mandatory testing tend to believe that things are already required to be really safe. People claim to be against increasing regulations, they want to deregulate, but then you ask about how much safety is currently required, and they perceive a huge amount of testing and regulation happening right now. And then when you talk about what they would want to see instead, they often paint a picture that involves more regulation than we currently have!

          UL doesn’t test for safety, they test for compliance with safety rules. Not the same thing at all. It should be expected that a new product might pass all the safety rules, and not be safe. That is expected; that is what insurance is for; that is why UL is owned by insurance companies! They don’t try to prevent all the preventable accidents, they try to prevent accidents with known causes from being repeated, without spending more money doing so that is saved in claims.

      1. On the one hand, if I installed this at home I’d be worried the house burned down every time I heard a fire truck.

        On the other hand, the risk might not be any different than leaving a tablet computer plugged in at home, or an alarm clock with rechargeable battery backup.

      1. I bought a weather station from them once. I was never able to get the wind sensor to link up with the indoor unit.
        The rain sensor supposedly linked through the wind sensor..

      1. I mean, if you are literally talking about a single LED, sure. But you can definitely get 200 lumen flashlights for $10 or so, which is surely what’s being referred to here.

        Whether the cheap LED actually IS 200 lumens is another story. But the same could be said for this bulb too really.

    1. 200 lumens is a theoretical figure that nobody ever checks. It’s essentially telling porkies for advertisement.

      3.7 V x 2 Ah = 7.4 Wh in theory, but in practice you cant discharge the Li-ion cell below 2.8 Volts or you’ll kill it, so the available energy to the lamp is about 3 Wh maximum, and it’s supposed to run for 3.5 hours on that, which means it has less than a Watt of power available. Now, there is no white LED in the world that does 200 lumens with less than a Watt.

      The true output of the light would realistically be around 75 lm.

      I had a lantern that was supposed to put out 300 lm with a 4 Watt LED, but somehow doing it while the LED is drawing only 1 Watts of power as I measured what it actually pulls from the batteries. Manufacturers can print anything they want on these things, or cheat by strobing the light and measuring the peak output.

          1. With those two 4.3Ω current-limiting resistors (0805s??) that Big Clive’s teardown shows, that’s predicting roughly 1/4W of heat in the two resistors, so somewhere between 240 and 350mA… so very roughly somewhere around one watt in the LEDs? Ok, sure, the 200 lumens figure has got to be unrealistic.

            Entirely aside from whether the battery in this device actually has the rated capacity, I’m still confused by this argument that a genuine 2A-hr cell only has half the rated capacity. Is this just a poorly-presented suggestion that the manufacturer is using inexpensive bad quality cells?

          2. Luke is wrong, end of story. A legitimate 2A*hr battery will in fact produce 2A*hr of charge before you reach the undervoltage limit (usually 3v per cell), at the specified discharge current (usually 1/10 the battery capacity). The available W*hr (energy) available will depend on the discharge characteristics of the battery, but using the ‘nominal’ battery voltage (usually 3.6v per cell) times the charge rating (2A*hr) should be accurate within about 10%. In this case, for a 2*Ahr 7.2v battery that would be a hair over 15W*hr.

          3. Yes – a legitimate one. That’s question number one.

            The second question is, do they have it fully charged? If the cell is sitting at 4.2 V then it’s going to self-destruct from the heat in a short order. If it’s not fully charged, then the average voltage is going to be lower, and the available energy less.

            Third question is, what’s the internal resistance of the cells going to be after n-hours in use? It’s going to reach cutoff voltage a lot sooner.

            Fourth question is, this is not at 1/10 discharge rate, but about 1/3 C where the nominal capacity does not apply.

          4. Also, the battery capacity starts diminishing from day one, so they can’t actually use the full capacity, unless they’re lying about the runtime too.

            But that’s something the consumers can actually try for themselves, so they’re more likely to lie about the light output than the battery life.

    1. This was my first thought. There is no isolation on that power supply PCB. Extremely dangerous to use when handling the powered device or connecting it to anything else.

    2. Looks like there is a direct connection between the “hot” side and the low-voltage side, through J4 (a zero-ohm resistor). Then there is the power-fail detect circuit, which probably puts a low voltage DC bias on the input through some moderate impedance, provided by the battery. Looks like this happens through R9-R12.

      This circuit should be treated with the same respect and caution as any other directly mains-powered circuit.

        1. Pro tip: look at the board before spouting useless nonsense. There is a 0805 packaged 0 ohm resistor (clearly marked) at J4. You can call it a jumper if you want, but the device there is unquestionably a 0 ohm resistor. They are commonly used as jumpers but that doesn’t them anything other than a 0805 0 ohm resistor.

          1. Sometimes designs need jumpers for various options, set at the factory on a per-production-run basis. Rather than mess about with pin headers, why not use existing pick and place machines to do the jumping for you? Hence, a small jumper in a surface-mount package, AKA zero-ohm resistor. I suppose it could be a zero-Henry inductor if you really wanted one.

            They’re also used to allow PCB tracks to jump over each other if it’s only needed in a couple of places, rather than add another layer.

          1. There is no electronic part in existence that is an exactly perfect implementation. This is literally the very first thing that is taught in any competent electronics class.

        2. Adobe/Flash hater: pro tip: usually means usually. In my long experience with industrial, military, and consumer electronics, “J” usually means “jack”, and “JP” means “jumper”. But often I have seen zero ohm resistors used (and have used them myself) as placeholders on a circuit board, where it may not be known until emissions testing, whether a particular signal needs a series resistor, an inductor, a ferrite bead, or nothing at all in order to behave well, so in this case the component really IS a zero ohm resistor, since it is meant as a component and not as an optional connection, which is what “jumper” would imply. Although I often call them jumpers out of laziness because “jumper” is two syllables and “zero ohm resistor” is six.

      1. But unfortunately the article implies just that:

        “A lot of people are hesitant to fiddle with AC circuitry, so the fact that this offers a turn-key solution and lets you focus on the DC side is a big plus.”

        Therefore I would not recommend this use of the device for people “hesitant to fiddle with AC circuitry”.

      2. It’s probably fine hanging from the ceiling, but I wouldn’t like to dick with it as a power supply for my own low-voltage stuff. Especially when USB adaptors are like a quid each now (ask Clive). Like the man said, it’s designed as a lightbulb, with the demands and typical use of a lightbulb. Take that away, and it’s not necessarily as safe as it should be.

        1. Yes, I understand. I just meant that for projects that don’t need to have wired connections to anything external to them, mains voltage is pretty docile: you just don’t allow the metal bits to be accessible. You’re right about USB power supplies being ultra cheap, and those ARE isolated. And as others have mentioned, if you need it to be uninterruptible, you can use a phone charger “power bank”, though you do have to find one that won’t turn off at the current your project uses. This sort of thing is just another option to think about. The more tools in your kit, and so on. I probably won’t use this approach myself, but I’m glad I know about it.

  2. Some phone battery banks might also do as a poor man’s UPS. Many of them will refuse to power a device as long as there’s power on the charge input. I don’t know if that’s inherent in the chip used, or set by jumper.

    I did get some Duracell ones at a discount place a couple years ago that will do both at the same time. They can power a RPi1 as a wifi hotspot for over two hours on battery. I did find that going from power to battery would reset the Pi, but a big cap should probably fix that.

    Ah yes, I did a project page for that: https://hackaday.io/project/3751-re-purposing-duracells-powermat-battery-pack

    Working with 5V feels safer, but I suspect the UL/CSA stamp on many USB supplies aren’t worth spit.

    1. It is worth saying that not all power banks can do this. Some simply have a charger IC and a step up converter, independent of each other. The problem is that running both the charging and the load will eventually time out the charger.
      The other problem is that even the ones that don’t have this issue will work as “on line UPS”, meaning that the battery will always be maintained full, which will kill the poor quality batteries quite fast.

    2. I think power banks are good as a power source if the thing you’re building can be built into the power bank, where you have access to the battery terminals themselves. This can be a challenge since these are usually designed not to be opened, but where there’s a will, there’s a way. Also, I’ve gotten a couple of different power banks off of Amazon that are basically just the electronics – they don’t include the Li-ion cells, and take standard 18650s in a case that can be opened. One of them works pretty well, the other doesn’t fully charge the batteries, but both room left inside the case for other electronics.

  3. Indeed, I’m fairly sure there is no isolation, since the detection of the power failure would be very difficult that way. Why would anyone design this with galvanic isolation? It’s completely unnecessary, complicated and expensive.

    I don’t see any other inductors, so I doubt that transformer is really just that; I suspect it actual is an air-gapped inductor, either a single one, or a coupled inductor with an airgap for a step-down flyback converter.

    I sort of expected the LEDs to be driven with a lower current, instead of having two sets of LEDs. With a flyback converter you could use the secondary winding as the storage coil for a boost converter.

    The detection of the power failure is pretty clever!

    While there is always room for improvement, this must be of the best articles I’ve read on HaD recently! Keep it up!

  4. > Without even opening the device, we can be fairly sure it will contain two separate arrays
    > of LEDs: one low set for battery, and a brighter set to run when the bulb has AC power.
    False. There are three ways of doing this. As you say: having a separate string of leds for battery operation. Second, Having say 4 strings of leds in parallel for normal operation and powering only one string with the battery But best for efficiency would be to just have the battery push only 20% of the current through the normal string-of-leds. The efficiency of the leds goes up and you end up needing less than 25% current to get 25% of the original lightlevel.

  5. “Never be in the dark again” might be a strong statement, usually they these LED bulbs come up with 5 years of warranty. Even-though they live longer then other conventional bulbs, but the lighting quality get dimmer over time.

    1. None of my LED bulbs get noticeably dimmer over time. If I buy them from the same batch, and keep one as a spare, when I install the spare it is the exact same brightness and color temperature. They work normally until one LED starts to burn out, then it flickers intermittently until that LED dies, then they stop working.

      OTOH if I go to the same store and buy the same brand of bulb at the same wattage and color temperature, then the new one is often brighter than the old one because the technology keeps improving incrementally. That’s why I switched to a brand where the model numbers follow the lumens and color temp; the new bulbs are closer in brightness to the old bulbs, but they use less power and generate less heat.

      1. The manufacturers of cheap LED bulbs always cheat. The testing standard for the lifespan measurement is down to 70% original brightness, but if the bulb is tested either as an “indicator” or a “decorative” light, then it can go down to 50% brightness and you don’t need to disclose that on the packaging.

        Most of the bulbs that are made to imitate regular lightbulbs are “decorative”.

        70% is the limit because humans are bad at judging brightness levels directly, since the eye rapidly adjusts to light falling on it. In absolute terms, there can be a vast difference between the old and the new bulb, but you don’t easily notice the difference. Your eyes just adjust to seeing in the lower light, and as a consequence you have a little bit harder time focusing or reading etc.

        One way to test absolute brightness is to face two of the same bulbs towards each other and put a sheet of baking paper in between. You can then move the paper to see from either side where the other light stops shining through. If it’s not symmetric, you know which bulb is dimmer.

  6. As other comments have already hinted:

    – The battery in a hot LED lamp is likely to be *at best* an early failure. Or burn your house down.

    “this board should be able to supply at least 400 mAh at 3 V.”

    And this system doesn’t have galvanic isolation from the AC line.
    That’s okay sometimes – you can run a microcontroller from a transformerless power supply or other non-isolated environment, but make sure you understand the consequences of that and what not to do.

  7. Electrician here. Just installed some LED recessed lights in my house. No battery backup. They are controlled by two Lutron “LED compatible” three way dimmer switches with a regular non-dimming four-way switch in-between. Yes, they are wired correctly, thank you;) With all switches in the off position, the LED’s will still emit light very dimly for about 10-20 min. Can’t quite figure it out, maybe a capacitor in the dimmer, some sort of induced voltage??? Doesn’t happen if regular non dimming three-way switches are swapped out. Tried different brand LED dimmers as well, same behavior. Any ideas???

    1. Electrician/electronics dabbler here.
      Seems to me that you have–short of replacing the electronic dimmers with another brand (which brand does NOT copy Lutron’s dimming circuitry/techniques)–narrowed the problem down to the dimmers.
      Replacing the dimmers would be fairly expensive. Ensuring that you used new dimmers which not replicate Lutron’s dimming technique would be very expensive (hardware designers copy ideas just as shamelessly as software designers).
      How badly does this bug you?
      (I’ll be the first to admit that I miss the obvious most of time–why’d you use a 4-way with two 3-way devices?)

      1. It doesn’t bother me really. It’s just the nagging why of it. These fixtures were from an electrical supplier, Lightolier Brand which is known for decent products. Surprisingly, I just swapped one out for a cheap no-name Amazon special I had from another job. This fixture/LED trim didn’t show the dim power off behavior. Sounds like bad driver design, maybe missing a diode?

    2. Also, when one dies pop the plastic top off, use a piece of metal to touch one side of an individual LED, and with the other hand touch something grounded. You can often test all the LEDs that way and find the bad one, if you want to use hot air gun to fix a few. They use cheap soft plastic on the LED body, though, so good luck!

      You’re basically always going to have a capacitor in there. If you can use a dimmer or not will depend on the individual bulb. I buy mine at a local lighting wholesaler that sells to the public.

      You should basically never need a special dimmer; the bulbs should conform to standard dimmers.

    1. The battery has built in over-voltage and over-current protection even if the application’s voltage or current regulation fails. You can look at the shape of the plastic at the top of the cell and compare it to the pictures of 803040-2P units for sale.

      If you want to start a fire, you need to install it into a recessed socket and make sure it is well-insulated. And even then, good luck! Maybe stab the cell with a screwdriver before installation?

    2. One of the two bought got really hot near the base (where the battery is, presumably) and was emitting strong smells of melting plastic. It was not in a recessed fixture, but upright in an in open lamp. I removed it, obviously and it’s going back to the store. Home Depot refused my negative review of the bulb too. Hopefully none of these will start a fire.

  8. PCB fab house worker here, CEM board with copper on one side is still called a single layer (/side) PCB. Having through hole components on one side and SMD in the other doesn’t make it double sided.

    1. And also, the LED board is made in Xiamen region, while the transformer board is made 600km away in Guangdong region in China. I’m used to seeing boards atleast made around the same region, even if the factory is not the same.

  9. During a power outage, the circuit remains closed? Is that typical? The majority of power outage in my home is due to circuit breaker, I guess this product won’t help in this situation?

    But I agree, this product has a lot of potential for magic performance.

    1. That will depends on the circuit. A blown breaker for this bulb that has nothing else on the circuit would look like an open circuit, this is true… But as soon as anything else is on that same branch circuit, you will have some easily measurable loads that will look like a closed circuit to the bulb.

      1. Closed circuit, yes, but not short. Measuring the DC line resistance of any circuit on a house during a power failure (unless the failure is a severed feeder wire) is basically measuring the secondary of the tranformer feeding the house, which is generally less than 1 ohm. A 100 W tungsten lamp with a cold filament has a DC resistance of about 30 ohms, which is easily distinguished from 1 ohm. The problem case is where there are devices plugged into the same switched circuit that have transformer inputs, since these will also measure short. Fortunately this is not a common thing.

  10. Hmmm… I think $12 is too much to pay for a 3v UPS. I mean it is fine if you don’t build power supplies, and simply don’t know how… But power supplies were the /first/ thing I mastered when I stole my dad’s soldering iron, and started building AC power supplies for my battery operated toys… I was 6… But lipo battery charging controller modules cost less than $2 each retail on Amazon, and you add a $2 lipo and a free wall-wart out of your wall-wart buckets (I salvage around 5 or 10 wall-warts every year, faster than I consume them, I sort them by output rating in my scrap buckets).

    When I was a young engineer working in my first engineering job, one of my bosses was looking to buy a bench power supply for $1200… I told him to hold off on that, and the nest day I came in with a completed power supply prototype that exceeded his spec, and when he later adjusted the spec for a new requirement, I made a small mod to handle the change. Power is the easiest part of any project.

    Project enclosures were always the hardest part for me… My stuff was functional but never pretty. Till I got a 3d printer…

  11. I purchase loose fittings easily available in India delhi. And short L&N points on led plate. Now I can use this bulb easily with mobile power bank. Instead of charging bulb simply use power bank.

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