A gloomy Chinese genius has made the incredible - a bicycle headlight on batteries that are not intended to power LEDs. I wondered how this miracle of Chinese thought still works.
This headlight worth less than a dollar (shipping is more expensive). The title says some kind of nonsense: "3000 lumens", "USB Rechargeable" and so on.
The description says "Battery Built-in (includes 2 2032 lithium batteries)". Of course, this is not a battery at all, but ordinary CR2032 coin batteries. Two pieces connected in series.
In fact, the luminous flux of the headlamp is on average 15 lumens (only 200 times lied). The light is very "cold" - 11500K.
The headlamp gives a small spot of light and is not very suitable for use, but I am interested in it in order to understand in what modes CR2032 batteries can work (I am currently testing them).
The CR2032 lithium battery is designed for very small currents: nominal current 0.4 mA, maximum continuous current 3 mA, maximum impulse current 15 mA (a source).
The nominal voltage of the CR2032 battery is 3 volts, two in series - 6 volts. When connected to a 6 V power supply, the headlamp draws 600 mA and this is 200 times the maximum current allowed for this type of battery. So how does it work? And most importantly, how long? Was it just a few minutes?
I donated two good IKEA batteries, used the EBD-USB + device as a voltage and current logger, and solved the Chinese secret.
When the headlight is turned on for the first time, it consumes 280 mA, the voltage on the batteries sinks to 3.58 V (1.79 V each).
After 10 seconds, the current drops to 156 mA, after a minute to 93 mA (the voltage is already 2.96 V).
It would seem a couple of minutes more and the headlight will go out, but everything works differently.
After 10 minutes, the current drops to 47 mA, and the voltage drops to 2.8 V (1.4 V on each battery, which is more than half its nominal voltage).
Further, the decrease in current and voltage slows down and the headlight begins to burn more or less evenly: in an hour and a half, the current drops to 20 mA (voltage 2.7 V).
After another three hours, the current drops to 10 mA, the voltage to 2.6 V.
The graph was cut off at this, since the device cannot measure currents less than 10 mA, but the headlight continued to burn.
17 hours after switching on, the current dropped to 4 mA, the voltage to 2.57 V. The headlight is still burning quite brightly.
30 hours after switching on, the current is 1.9 mA, the voltage is 2.55 V.
Two days later (!) The headlight is still on - the current is 0.9 mA, the voltage is 2.52 V.
After three days (!!!), the current dropped to 0.3 mA, the voltage to 2.46 V.
The LED is on, but the headlight practically does not give any light.
Surprisingly, despite the prohibitive operating modes of the batteries (exceeding the maximum current in dozens of times, voltage drop more than twice) this "miracle of technology" continuously worked three days. Surely in normal operation, when the headlight turns on for half an hour or an hour, and then the batteries "rest", it will work even longer.
Oh, those Chinese.
© 2021, Alexey Nadyozhin
For ten years I have been writing every day about technology, discounts, places of interest and events. Read my blog on the site ammo1.ru, in LJ, Zen, Mirtesen, Telegram.
My projects:
Lamptest.ru. I test LED lamps and help figure out which ones are good and which ones are not.
Elerus.ru. I collect information about domestic electronic devices for personal use and share it.
You can contact me in Telegram @ ammo1 and by mail [email protected].