128 LED flashlight !?!

[Analog]

only 6AA cells?

How do you think they wired it?

https://powerlong.en.alibaba.com/pr..._Flashlight/Aluminium_128_LED_Flashlight.html

 

[Andy1845c]

haha, i'd like to know. Seeing as how much troble I am having trying to design somthing with twice that many from a 12v car battery.

Its quite the flashlight though. I wonder how bright it really is.

 

[Hero999]

Sounds pretty pointless to me.

Perhaps it powers all the LEDs from a low current so they work at maximum efficiency.

 

[audioguru]

White LEDs are about 3V at low current. They probably connect them in two groups in series. The LEDs in each group are all in parallel and the maker hopes that only a few burn out and that you don't notice. Then they use a single current-limiting resistor.

AA cells can't provide much current so 128 LEDs is rediculous. Only 20 LEDs operating at 25mA each will be extremely bright.

 

[eng1]

There might be a IC converter that doubles (and inverts) the voltage. The LEDs might be multiplexed in 2 or more groups, I guess.

 

[Hero999]

How do you and audioguru know this?

Have you seen the schematic or opened one up?

 

[eng1]

How do you and audioguru know this?

Have you seen the schematic or opened one up?

I was just guessing - as I said. Stepping-up the voltage and multiplexing is the one solution that came to my mind.

 

[audioguru]

6 AA alkaline cells provide 9V for a few minutes then drop to 6V in 2.5 hours with a 500mA load. LEDs in parallel and with two groups in series will be about 6V and a single current-limiting resistor sets the current.
With 64 LEDs in each group then each one will have a max current of only 7.8mA.

 

[RODALCO]

I raised the issue in a previous thread re a 31 LED torch too.
That one drew nearly 1 amp from 3 x AAA batteries and the batteries did not last at all.
I changed the handle completely to take 3 C cells and it runs fine.
The LED's are fine, the battery capacity was well underrated.

This 128 Led beast is probably the same. Ideally it requires C or D cells to get any proper use out of it. AA's in that case are also heavily underrated for that high demand.

 

[audioguru]

These little LED flashlights need an automatic battery changer mechanism.

 

[Overclocked]

These little LED flashlights need an automatic battery changer mechanism.

Solar Power. Or Mechnical power (wind would work). Or of course, a wall wart.

 

[audioguru]

There isn't any solar power when it is dark. If there is sunlight then the flashlight wouldn't be needed.

I have a pretty big 1.8W solar panel. Its current is rated at 150mA but the max I got through a closed window at noon was only 50mA. It produced 100mA with the window open. The window was clean. An hour later the current was half.
It would take weeks or months for some little AA 2500mAh Ni-MH cells to fully charge.

Drag an extension cord around behind a flashlight?? I don't think so.