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I am working as a night delivery driver and when its dark and/or rainy it's almost impossible to read many of the house numbers/names I am looking for.

I've heard of Maglite and in fact my friend has a large Maglite which is 680lm and very powerful but it cost him a fair bit and uses huge batteries.

I look on auction website and see ones boasting 900,000 lumen output! (for about £5 :D) I then google 'worlds most powerful flashlight' and it seems one made by 'Wicked Lasers' is considered one of the most powerful at 4,100 lumens. (https://www.wickedlasers.com/torch)

So why on auction site are they allowed to state 900,000 lumens. And how can i trust the output specs on any advert? (is there any other spec I should be checking)?

Really need it soon, and I need to be able to see stuff that is about 20-30 metres away in heavy rain at night.

Any help would be greatly appreciated. Thanks

(Ps. I could put links showing the adverts boasting 900,000lm but didnt want to put their links anywhere in case they are a scam)

Additional Edit:-
Well I have continued looking and the specs vary massively. This one I am thinking of buying boasts 20,000 lumens and 500m range. But it only takes 1x AAA battery ??!?!? - Surely this cannot be 20x more powerful than a top Maglite? https://www.ebay.co.uk/itm/Tactical-20000LM-L2-Zoomable-LED-Flashlight-Rechargeable-battery-Torch-with-BOX/322609536378?epid=16031184130&hash=item4b1d06dd7a:g:SwQAAOSwmcNdIJWc)

Conclusion:
For what it's worth I decided not to buy a 'No-name' brand. And after finding this one at Toolstation: https://www.toolstation.com/ledlenser-tt-police-tactical-torch/p41307
I realised their pricing is actually very competitive. It is a few quid cheaper in Toolstation than the same torch is on Amazon or ebay.
I can just go into the shop and buy it today :D

I am happy now, thanks again all you guys. PS. You have inspired me to begin learning electronics as a new hobby too

Well in your eBay-Link they are providing enough material to debunk themselves. They say they use a Cree XM L2 LED. So let's just look up what that thing can output.

Datasheet XM L2 LED and we see: even if it is driven with 2000 mA - which is quite the stress on the battery - it outputs 600 lm.

And they kindly provided a picture showing that they only use one LED and not multiple.

So they are lying or they measures the first production batch in unison and forgot to say they used 400 of these things.

Generally, you can expect around 100 lm / W and a handheld device is probably using 10 W maximum (okay might be 20 W or so with a good battery), so anything beyond 2000 lm is just unrealistic.

If they tell you the 4000 mAh battery will last 6 hours, you can calculate the wattage:

4000 mAh / 1000mAh/Ah * 3.7 V / 6 h = 2.5 W.

So 250 lm would be a realistic guess for the brightness. And yes, the 4000 mAh are faked as well - currently 18650 LiIon are around 3200 mAh maximum.

Okay, so how does the "brightest torch" from wicked lasers hold up with these estimates?

They claim 4100 lm using a 100 W OSRAM halogen bulb. The datasheet of that bulb tells us it emits 2800 lm. The 4100 lm is still a realistic number though, the bulb will emit light in almost all directions and with a reflector (which are 90%+ efficient) you can send more light in the right direction, which increases the lumens in that direction. With LEDs this effect is not as pronounced as they already have directed light (120° cones are typical).

What about the power of this thing? They claim 100 W which sounds ridiculous. But they use 4 18650 batteries in series and give a low estimate of 20 minutes lifetime. Sadly the capacity is not given, but this is a really high current application, so the capacity will be a bit smaller - I guess 2500 mAh for a high quality cell.

4 * 2.5 Ah * 3,7 V / 20min = 111 W

So the math actually checks out and I think that it does what they say.

TL/DR: It's a scam.

Long answer:

Current LEDs that work well in flashlights have luminous efficacies in the 100-200 lumen/Watt (roughly, not factoring in driver losses etc).

Thus a 900 000 lm flashlight would require 4500-9000W of power... thus a huge battery and about the same cooling fan as a hairdryer.

Also LEDs for flashlights are usually rated between 1 and 10W and a common LED power for a flashlight is 3W. So if you look at the flashlight and only see ONE LED in it, and it is rated for more than 1000-1500 lm, expect trouble!

Then you can check for battery lifetime. An AA 1.2V 2500mAh alkaline can deliver about 3 Wh (Watt Hours) of power which means 3W for 1h or 1W for 3h, you get the idea. So a flashlight with 300 lumen (about 2-3W) with a battery life of 2 hours on 2 AA batteries sounds good. A bit optimistic considering AAs lose capacity at high current but... not in scam territory. If it is advertised for 1000 lumen and 10 hours battery life on 2 AAs, then... you know something's off!

Lumens describe the total amount of light out of the flashlight. Candlepower (candela) is a misleading number as it describes lumen/steradian, ie light flux in the beam. The same LED, same lumen, will have much less candela with a flood optic than with a tight beam optic, because the tight optic concentrates the light more. Using candelas is a good way to get impressive numbers which look good!

Also cheap flashlights tend to have gotchas, like no spring contacts for the battery, so when you shake it a bit it will turn off or switch to blinking mode.

In other words, go to a flashlight geek review site and pick one by a good manufacturer.

So why on auction site are they allowed to state 900,000 lumens.

How is ebay supposed to check?

If you want a good light, first decide on the batteries you want. 18650 Lithium are better, especially in the cold, but require a specific charger. NiMh AAs are more convenient, but lower capacity.