Power Bank Light Maximum Lumens ?

[Richwouldnt]

What is the practical maximum lumens likely to be available from a USB power bank capable of outputting circa 2 to 2.4 amps from a single output port to a LED light head. I have seen some light heads for use with a USB power pack that are claiming 2000 Chilumens which I am sure is total BS!

[Phlogiston]

I have an XTAR UL1:

https://www.gearbest.com/led-flashlights/pp_144657.html

which was reviewd by JohnnyMac on CPF:

Review: XTAR UL1 Multi-usage Mini USB Light

It’s specified for 180 lumens maximum, and it can get very hot when it’s being used at that level. Given that a Convoy S2+ can only sustain about 400 lumens in continuous operation before it starts to get unsafely hot, that 180 for the XTAR is probably the most you can get away with in the USB plugin form factor. After all, the Convoy has a lot more metal and surface area to get rid of heat with.

I also have a Xiaomi USB light:

https://www.gearbest.com/electronics-gadgets/pp_280338.html?wid=21

which has been tested by BLF member sixty545 to have a similar maximum output:

Does anyone have a Xiaomi USB LED light?

[Edited: Added memory and current draw] I have one of those new ones. It is very nice and with 10 LEDs (old one 6). The greenish tint is gone and it cycles through 5 levels (with a push button) with memory: (OFF) - 0.5 - 8.1 - 39 - 107 - 169 lumen (against the old ones 87 lumen) measured in my integrating sphere (a little difficult with the long head, so I put it partly into the sphere). The color temperature was 3700K (The old one 3560K). Current draw was 0.09 - 0.11 - 0.18 - 0.24 - 0.46…

I would say that considering the XTAR and the Xiaomi together reinforces 150-200 lumens as the likely sensible maximum for USB lights in either form factor.

[Richwouldnt]

@Phlogiston

I have an XTAR UL1:

https://www.gearbest.com/led-flashlights/pp_144657.html

which was reviewd by JohnnyMac on CPF:

Review: XTAR UL1 Multi-usage Mini USB Light | Candle Power Flashlight Forum

It’s specified for 180 lumens maximum, and it can get very hot when it’s being used at that level. Given that a Convoy S2+ can only sustain about 400 lumens in continuous operation before it starts to get unsafely hot, that 180 for the XTAR is probably the most you can get away with in the USB plugin form factor. After all, the Convoy has a lot more metal and surface area to get rid of heat with.

I also have a Xiaomi USB light:

https://www.gearbest.com/electronics-gadgets/pp_280338.html?wid=21

which has been tested by BLF member sixty545 to have a similar maximum output:

Does anyone have a Xiaomi USB LED light? - #50 by sixty545

I would say that considering the XTAR and the Xiaomi together reinforces 150-200 lumens as the likely sensible maximum for USB lights in either form factor.

I agree and have two of the XTAR UL1 units as well as one offered by Ravpower at about the same time. Excellent little lights. Currently some Chinese sellers are claiming 2000 “Chilumens” for some current but physically slightly larger, based on photos, similar units. Considering that the UL1 only drew about 1/2 Amp at 5 volts as I recall, or the maximum for original USB 2 power output rating, I wondered what the theoretical output could be for one that drew the 2+ amps at 5 V that modern USB ports can provide. Definitely higher than 180 Lumens apparently if the user and power source can stand the heat.

If the UL1 could produce close to 180 lumens from 2.5 watts then a 10 watt power draw should be able to produce circa 720 lumens, and melt in your hand potentially. At 2.4 Amps, obtainable from some current USB sources, the theoretical light output approaches 800 Lumens per my calculations.

[Richwouldnt]

I checked current draw on the Xtar UL1 in turbo mode and it is about 0.45 amps at 5.05 volts attached to a fully charged Anker 13,400 mAh power bank and .31 amps in High mode. Per JohnnyMac’s test on CPF that is 131 Lumens on high and 173 on Turbo. Used an inline USB voltage and current tester for the readings, a new one that can handle up to 3 amps current at 3.2V to 15V per the specifications listed. The Ravpower light draws about 0.21 amps on High. Be interesting to compare them to the new ones I have ordered when they arrive.

[hIKARInoob]

P = 5V * 2.4A = 12W
If you look at something like a Creee XHP70.2 emitter, efficacy is 181 lumen/Watt. That’s the ideal value with low output. If you stick with something like 150 lumen/Watt, then your nominal max output will be 1800 lumens give or take. Driver efficiency of 85% results in about 1500 lumens.
This value is about double compared to the calculation above with the UL1. I don’t know what leds are used in the UL1, but I can imagine both leds and driver are a bit less efficient than what is possible, as the UL1 is probably not designed to be super efficient.
Of course, with this kind of max output you need good heat sinking etc.

[Richwouldnt]

@hIKARInoob

P = 5V * 2.4A = 12W
If you look at something like a Creee XHP70.2 emitter, efficacy is 181 lumen/Watt. That’s the ideal value with low output. If you stick with something like 150 lumen/Watt, then your nominal max output will be 1800 lumens give or take. Driver efficiency of 85% results in about 1500 lumens.
This value is about double compared to the calculation above with the UL1. I don’t know what leds are used in the UL1, but I can imagine both leds and driver are a bit less efficient than what is possible, as the UL1 is probably not designed to be super efficient.
Of course, with this kind of max output you need good heat sinking etc.

Thanks. My brightest USB powered light is a bicycle headlight that draws about 1.10 Amps at 5 volts from a Anker USB battery unit. Compared to normal flashlights I estimate it is about 400 lumens maximum. Eyeball estimate from a ceiling bounce.