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After the initial disappointment of finding out that this light was about half the size I was expecting, this light just kept delivering hand-to-forehead moments.
Spoilers below:-
The solar panel. It's tiny, with about 20mA output, which is going to take a while to charge the 2200mAh lithium cell. But that's probably a blessing in disguise, since there is absolutely no overcharge protection for the lithium cell from the solar panel.
This light has all the obligatory flickery dim modes, annoying strobe and the worst implementation of an SOS mode I've ever seen. The circuitry uses a P-channel MOSFET switching to the positive rail, but the software appears to be designed for an N-channel MOSFET switching to the negative rail, which means off and on are inverted. This doesn't show on the main modes that have been shuffled to fit, but the SOS mode doesn't actually flash the SOS code, but blinks the light out for dots and dashes instead.
Given that the dimming options are just full half and quarter, the PWM (Pulse Width Modulation) routine doesn't have to be complicated. It could alternate toggling the LEDs on and off with switch tests and still achieve a very high PWM speed on a slow processor. This software has very slow PWM to the point of being unpleasant.
The light does have some plus points though. The cell capacity can be doubled, and the 5V power bank mode puts out 5V all the time, albeit at just 800mA. But it does mean the light could be used to power low current LED strings for a long time without going into standby.
With a voltage of 4V the LED current measurements were:-
Full 900mA
Medium 450mA
Low 236mA
Strobe 450mA (50/50 ratio)
There's no magical keyword to find these lights. The title is a fairly generic string of words:-
USB LED Rechargeable Outdoor Camping Tent Lamp Lantern Hiking Ultra Bright Light
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This looked a lot bigger on ebay, i have to say, but having said that, having looted the listing for this little sort of almost like a little high b light for camping uh, it is the correct size. As listed they don't tell you the battery capacity. I've tested the battery capacity, it's rechargeable uh, just over two amp hour, which isn't too bad. It has these little solar panels.

It's got one two, three, four: five, six, seven, eight nine ten five volts, so that will be uh charging the lithium cell inside, although i would rate these at something like 20 milliamps tops. So, given that it's a 2000 milliamp hour and this 20 milliamps, it would take about 100 hours of direct sunlight to actually charge this up fully. So they're kind of just almost like a gimmick, is available without solar panels. It's also available available without the remote control, but let me demonstrate some of the features i shall rip the little tab out of this right features on that's a useful enough feature off uh mode.

One is low, it should say it's medium and mode. Two is low and, as you can see, it's possibly modulated, so you get that striping and uh. Then you've got mode three, which is straba scope and the just sos now see if you can tell what's wrong with sos i'm pointing this away from the camera. To avoid uh causing excessive uh strobing doesn't look quite right.

Does it what if i tell you that it's inverted sos and it's actually blinking out for the dots and dashes, instead of actually lighting for them, which is not a very efficient way of doing it? If you use the button on it, you can step through high medium low, strobing and sos, which means that if you're camping and it's like good night honey good night, i'm going to turn the light off and it's like click, click, click, uh, stroboscope. And then it's like before you can actually turn it off. It's got that annoying feature. The thing has a usb output.

I did not test that. I suppose i could test it. Where is my little tester ed one moment please, the tester has arrived. Let's zoom down in this, so it doesn't make bold claims.

Is that visible? I shall shoot it with my hand, can kind of make it more visible. Let's turn it up. It's only rated, i think, about 800 milliamp output, i'm not really sure we'll find out. It's currently at 4.8, 4.9.

That's doing. Okay, 4.9 volt! That's acceptable! It's at 700, milliamp 4.9 uh at 4.8, pretty much on the button. It starts dropping off. Let's wind it up a bit more and it still holds yeah.

It's dropped down down to about 4.6 volts at one amp, so not really super mega high output, but still useful. You also have the option of charging with a usb lead which is supplied, and it's got that uh. The charging status uh thing right, too hot. Let's uh zoom back out again bring in my spudger.

I know how to open this, because i popped the lid on one of the live streams. You pop your spudger in and it just pops out. That's nice there's the infrared receiver. Oh, that is quite a lot of leds.

Tell you what let us uh pop these little screws out and see? What's underneath, is it going to be an 18650? Is it going to be a rectangular cell? It could fit an 18650 in there. So, let's pop the last screw out and then gingerly lift this up. I shall lift up by the infrared thing. Two eighteen six fifties: oh they must be pretty much one arm power.

Each okay right, tell you what it is time to explore this circuit board. It's got a little uh, maybe that's a charging control chip and that will be one of those universal uh. I'm not really sure right. Tell you what one moment please i'm going to explore this.

Okay, let's explore so i've got the two sides of the circuit board. This side is reversed, so it matches uh component for component down to what's here. So when you see this groover pleated through holes, that's this group of plated through holes here it just makes it easier to trace out the circuitry is divided into two sections, pretty much right down the middle. Here we have a standard power bank chip, something like you'd find among these generic littles of one amp output, power, banks, um and it's uh is basically completely separate from this.

Although the microcontroller they're using does uh get a signal on two lines from the power bank chip just to tell it when it's charging discharging the microcontroller controls the leds via this mosfet down here and this series resistor, which is 0.68 ohm. But it also controls the four leds and also decodes the infrared receiver, which is on the other circuit board, the actual led circuit board. So when it's displaying, when you press the button to wake up and see what charges in these leds, as far as i can see, the five volts always active over here, because it's not connected in any way to these leds, that's purely being measured by the microcontroller. So let me bring in the schematic.

We start with the power bank chip. Note these scruffy dotted lines. I kind of regretted that they're ugly but they're connecting the output from the the power bank chip over to the microcontroller just to tell it when it's charging discharging it indicates and it can does its little light show. I should draw a couple of led arrows down there, so the usb in for charging has a little uh filter on a 1.5 ohm 2.2 meg fired very common, and then it goes to this chip and that then regulates the charging of this lithium cell.

With a 10 meg fired capacitor across it, when you plug something into the usb out, the chip is one of those ones. It just keeps it topped up to five volts as far as i can see, and it uses this little inductor here, 2.2 micro henry pulses. It to actually boost the voltage off under this capacitor and provide the 5 volt output. The charge and discharge lines that go over to the microcontroller have two pull down: resistors normally they'd be used to drive leds directly.

This is the actual data sheet of that chip. It's in chinese because it's not really aimed at us it's aimed at manufacturers, but there's the two leds. That would normally be the ones that, in the case of this little power bank, they usually shine through from the back and it's like say red for charging. And then it's blue for discharging that's, basically those lines but they're just being used as signal the microcontroller.

The mystery microcontroller has a button for selecting the modes, it drives the mosfet and it's noting notable. This is a p-channel mosfet, it's an a1shb which is the p-channel version of the n cha n channel a2 shb. And i wonder if that's why the sos is completely upside down, because it's almost as if someone wrote this modified the software that was originally designed to drive an n-channel mosfet and if they shuffled the things like full-on uh, for instance. If, if this was an n-channel mosfet being driven when you went put it into full intensity mode, you'd actually take the output, pin controlling it high and that would switch the mosfet on in the case of the p-channel mosfet, it's switching to the positive rail.

So you actually pull it low to turn it on. So i wonder if they've shuffled things in this chip in the software so that they say, for instance, full-on actually now becomes full off, because it's the opposite polarity and vice versa and the because of the uh pulse of modulation, say, for instance, at a low setting. It might have normally been doing this pulsing modulation leds to make them dimmer. That would actually effectively be on here instead of there.

So if that was the low setting, that would become medium setting and vice versa, and that would explain why the sos mode, instead of flashing on off it's actually blinking out. I do think that they've just shuffled the software and it's actually designed for driving an n channel mosfet, the four leds down here - they've, just a one k, resistor each but there's also another one key resistor coming from the solar panel, and this is where it gets. A bit awkward because it would have been nice if the solar panel had fed over to the usb in so it could regulate the charge to the lithium cell, but in this case it's just going straight through a diode to the lithium itself. So, technically speaking, although the output is very low, at only about say, 20 milliamps uh, if you left this thing on a windowsill in bright sun sunshine over time, it could potentially overcharge those cells, particularly if they were already ready fully charged in the first place.

It's kind of odd, but the solar panel also has that 1k resistor so that with the slightest sniff of solar energy, just even room lights, it will also make this led glow gently just to put on a show. The other thing is the infrared sensor, which is on the led circuit board. There's 60 leds in this board. Apparently that's quite a lot.

It says 60 led down here, um, odd um, but uh. The infrared sensor has a little decoupling, capacitor mounted locally, just literally between the pins in here, and it's got to connect across the battery and then it signals back to the microcontroller, and that is about it. It's a very strange little thing. The whole uh morse code thing is very weird, like the person who designed it didn't really know how to tweak the software to to get the desired result.

Overall, uh, it's a hackable in the sense that the it's it's got room for two 18650s. It might be a good idea to just disconnect in the solar panel, unless you know you're, just gon na leave it in a darkish place, but you could theoretically put 2.2 amp hour cells in here and a pair of them that would uh pretty much double the Capacity, i'm not sure what the panel will get technically speaking, it's 0.68 ohms, so technically speaking a fully charged battery 4.2 minus the 3 volts. The leds 1.3 volts divided by that 0.68 equals 2 amps. Theoretically atop which uh for the leds would be.

It would be dissipating about six watts in that panel. That's quite high. I don't know if there'll be other losses that will actually reduce that um, but there we go. It's a smart enough little light, but it has defects as they usually do, but it has got the facility that you know you could uh hack it to the green.

It's got the advantage that uh, because it uses a standard, little power bank chip in here. It will always be putting out that five volts uh, which means it's or you know if you just had low level ambient lighting it'd, be perfect just to plug them into this, without using it as a main light. But there we go it's uh, interesting light. It has its defects, it's quite novel defects, but it does have a certain element of hackability um.

You get options, you can buy it without the solar panel. That might be a good idea. Oh the uh. There's a charging jack, that's kind of a blocked up.

Well, that's the button: where is the charging jack the charging jack is under here that little hole there? It's designed clearly to take a 4.2 volt output charger. It's not something you could just plug a usb output straight into that charging jack on the circuit board. It pretty much connects across the lithium cell again, so it would have to be the proper charger, but that's it. It was interesting.

It was certainly worth taking apart and reverse engineering.

10 thoughts on “Rechargeable camping light with weird design flaw”
  1. Avataaar/Circle Created with python_avatars Shared Knowledge says:

    This is typical of products designed by people with little understanding of much of anything except how to try to cobble something together from trying to copy other successful designs even if they get something as simple as SOS signaling complete backwards. This is why not to buy no-name anything from eBay unless you’re fairly certain it will actually work right, not electrocute anyone, burn your house down, etc. A lot of eBay Chinese products are a complete fail in one or more of these areas with little realistic recourse for the buyer. It’s like the difference between say a Fluke test instrument and one made by “Hopi” or “Americal” in that you almost get what you pay for.

  2. Avataaar/Circle Created with python_avatars Jonathan Hammond says:

    The international outdoors distress signal is six blasts on a whistle, six shouts, (or other noise), or six light flashes, repeated at intervals of one minute. The response is three of the same. Flashing SOS is not an officially recognised signal.

  3. Avataaar/Circle Created with python_avatars Anthony Barker says:

    Had they made this without the SOS and strobe and added USB charging it would pretty much be the perfect camping light… I would even accept them adding red or blue LEDs for "night vision" if they needed to add a gimmick feature. I'd replace the two 18650s with a single 5A 21700, looks like there is plenty of room.

  4. Avataaar/Circle Created with python_avatars RC Hobbyist Extreme says:

    I see no use for the solar panels in that as most people use those under a canopy. Completely useless function. That SOS feature is garbage as well. What's wrong with a simple camp light? Probably China made as well.

  5. Avataaar/Circle Created with python_avatars immrnoidall says:

    Someone could simply ad a 1S ,BMS for 50 cents and a jack for a useful exterior solar pane / charger. I do a similar hack with cheap solar lawn lamps so I can put the little solar panel on or out the window, for a light inside ,a few feet away. Add a switch to the light and it's always charged when needed.

  6. Avataaar/Circle Created with python_avatars Shinigami Lee says:

    Here's a million dollar idea for these manufacturers. Stop wasting your valuable time and money building strobe and sos features into your product designs. NOBODY HAS EVER USED THOSE FEATURES AND NEVER WILL!

  7. Avataaar/Circle Created with python_avatars Alex says:

    I'm surprised they didn't just use the powerbank chip and hookup the leds to the flashlight capability many of the powerbank chips have. the sos is useless and some analog way of dimming the leds could be used

  8. Avataaar/Circle Created with python_avatars Abderrahim ZAIDANI says:

    Hello Clive,

    I have just bought a similar lamp, but i realized that the light lamps is reduced to low light after 10 to 15 minutes from high light mode. So i had to always click on the maximum button to make it in higher light mode again which will stay another 15min and so on.

    Did u remark the same behavior on ur side ? If yes how could we solve that annoying problem in ur point of view ?

    Thanks a lot

  9. Avataaar/Circle Created with python_avatars Picobyte says:

    As usual with backengineering these chinese 'marbles', you are right. They forgot to invert their software states when changing to that inverted output.
    It's behaviour matches all your descriptions, ad an inverter to the output and all does fine.

  10. Avataaar/Circle Created with python_avatars Ian Hosier says:

    That solar panel is going to contribute absolutely nothing to the charge of the battery. The larger side should be a decent size solar panel and the small side should be a single LED, then it might actually be useful

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