I got several LEXXA 7W LED-VARAVALO bulbs in hoping to replace some aging LED light bulbs with new ones that have a bonus feature: They have an internal battery that allows them to output light even when the mains power is turned off. Those were available cheaply from Finnish shop Motonet (bulbs with pretty similar look and similar features are also in Amazon).
The marketing promise is good: LED bulbs with integrated lithium-ion battery can provide up to 5 hours lighting during blackout and power outage. White LED light bulb functions like a regular LED when connected to household electricity. Bulb can be activated in the event of a sudden power outage from normal light switch. The light bulb can be used as flashlight for home or outdoor (comes with switch socket for that).
Here are some pictures of the products:
Here is technical data from product page translated to English:
- 230V 7W 500lm
- Li-on Battery 1200mAh
- Stock E27
- 65mm x 117mm
- Warm white 3000K
- Radius angle of 120 °
- It can not be dimmed
- Action time up to 5h
- Charging time 5-10h
- Including E27 switch / suspension strap
The idea sounds brilliant. The bulbs works nicely as normal LED bulb with mains voltage:
It gives out light (power from internal battery) when screwed with holder that come with the bulb:
I could even turn o the bulb with my fingers!
I did some measurements how the light bulb reacted to different loads between pins on the base:
When the resistance was from short circuit to 470 kilo-ohms, the bulb was fully on. When the resistance was one mega-ohms, the bulb gave some very dim light. With bigger resistance values, no light output.
I also measured that the bulb pushes out around 2.5V DC (open circuit voltage, plus on center of base) to the bulb base to try to detect if the light switch is closed or not. The output current is very low, about 3.3 micro-amperes to short circuit.
To this point good. Good idea, but it is failing on one big issue: it does not always reliably turn off when the light switch is turned off.
This is pretty annoying. When I want to turn off the bulb, it could turn sometimes off, sometimes does not turn off, sometimes gives some dim light then turned off. Very annoying and will use the stored energy (that should be there for emergency).
What causes this issue? I tried the bulb on several lamps with wall switches. Pretty much same results. And this was a new house I tested with wiring made well. No other load on those light circuits. Tested on two light circuits. Tested with two different bulbs. All this to eliminate that there was a single mistake (bad lighting circuit wiring or damaged product).
Then I took the bulbs to the lab and made some measurements. I tested ow the bulb reacted to AC frequency (50 Hz) signal coming from bulb base into bulb. I noticed when then AC voltage goes to around 3V RMS, the bulb turns dimly on (consumes power from internal battery) and then AC voltage reaches 3.5V RMS the bulbs turns fully on (to brightness it operated normally from internal battery). So this indicates that getting few volts of noise on incoming wire can turn the bulb on. I tried to measure the input resistance and capacitance of the bulb to low voltages: the resistance seems to be infinite to several mega-ohms and capacitance was 27 pF. At this high impedance input on the bulb to sense something, it is no wonder that it can pick up few volts of noise on floating mains wires in mains wiring bundle. This product does not seem to have robust enough design for reliable operation in real-life use cases I have.
I was not satisfied with the results. Those bulbs are not very useful to me. Not completely useless (they work as flash lights), but not very useful. If those were built with more robust detection circuit, those builds could have been very good.
Verdict: Not recommended because bubs fails to often turn off properly when it should.
Question: Are there any better similar products on the market that do well what they promise? (Free samples for testing are well-come for review)