This version of the now classic “intelligent emergency lamp” has the most minimalist circuitry seen yet, and what appears to be an SLA (Sealed Lead Acid) battery. In one area it has cut cost a bit too much and in another area it is fiendishly clever in using just a single transistor in its active circuitry.

I just had to take the lead acid battery apart to see what was inside. Mainly lead and acid apparently. Quite a lot of lead too – I guess they have to get rid of all that lead somewhere.

Ladattava E27-kantainen 7W LED-lamppu. Soveltuvuus: turvavalo, taskulamppu, telttavalo, terassivalo, yleisvalo, työvalo. Lataa lamppu normaalissa E27-kantaisessa valaisimessa, ja käytä latauksen jälkeen jopa viisi-tuntia. Sähkökatkon sattuessa, voit käyttää lamppua normaalisti valaisimen kytkimen kautta.

https://kauppa.srsfennoel.fi/lexxa-led-lamppu-e27-7w-230v-akku-1200mah.html

This version of the now classic “intelligent emergency lamp” has the most minimalist circuitry seen yet, and what appears to be an SLA (Sealed Lead Acid) battery. In one area it has cut cost a bit too much and in another area it is fiendishly clever in using just a single transistor in its active circuitry.

Comment:
“This is exactly what my lamp circuitry was like… but mine uses 18650 cell without protection instead. That SLA battery is very common in cheap Chinese flashlight or mosquito racket because they’re cheap and don’t require protection to charge, they usually just get charged by a capacitor dropper like that but I haven’t seen one venting or oozing out electrolytes though.”

Although I’ve featured this style of lamp in the past I’ve never done a full reverse engineer of the most common type. So here it is. It’s one of those products that achieves economy through clever tricks that take a moment to get your head around.

So look for listings where they show someone bridging the cap with their fingers or with the screw-on switch cap to use it as a rechargeable work light.

Investigating the Tiny Salvaged UPS from a Lightbulb
https://hackaday.com/2018/05/21/investigating-the-tiny-salvaged-ups-from-a-lightbulb/

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 bulb drops down to 200 lumens when in battery backup mode,

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.

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 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.

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.

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.

The video also has my take on the cheapest and possibly tackiest Chinese style emergency light circuit possible. Like a challenge to design an emergency light with the minimum amount of components possible.

But in my last-minute addition there’s a design flaw. With the LED in series between the switching circuit and the cell, the voltage available to turn on the transistor would be so low that it would probably allow the LED to glow, but not light fully.

Inside an “intelligent” emergency lamp with schematic.
https://www.youtube.com/watch?v=rcKbLnUz1bI

I have to admit that this is a very clever idea. It’s a standard LED lamp with the addition of a lithium cell. In normal use it charges from the mains while lit, but in the event of power failure it will light up automatically, but only if the wall switch controlling that light is on. That basically means you can turn it on and off from the light switch even when there’s a power cut. It does this by applying a small DC voltage to the lamps contacts and detecting if it is bridged. If the wall switch is off then no significant current will flow, but if it is on then current will flow through other appliances and circuits in the house and it will detect that and light.
This does mean that it can only really be used in a single lamp holder on its own, and the switch can only be a simple one with no active electronics.