How does one flashlight manufacturer get 10hrs runtime at 40 lumens out of a AA battery and another only manages 2hrs at 35 lumens ? i’m thinking of the Sunwayman M10A and the Skilhunt Ramble , keep it simple boys and girls
Easy…… telling porkys on the spec sheets 
Even allowing for telling porkys such a big difference don’t get it
well im no expert by a long shot but id say its got to be down to something to do with how they are driven??
We don’t know how honest these lumen counts are. If they are wrong, then you aren’t comparing apples to apples. Also the LED used matters, a more efficient LED will use less power resulting in longer run times. Also the driver uses energy, a more efficient one will use less power leading to longer run times. And last but not least the batteries used, alkaline, zinc-carbon, NiMH or lithium, and they all come in different capacities, i personally own some 1900 and 2650 mAh NiMH.
both them lights use xpg-r5 so that narrows it to driver or the claimed lumens not being correct?? or possibly a misprint in the specs…… iv seen an example of this on a trusted uk flashlight site…
wrong lumens….by a lot!!!
Right so my example probably isn’t fair to the manufacturers , i understand now thanks Bort
40lm OTF for the XP-G R5 requires ~120mA to the LED, that’s ~250mA from a NiMH battery. Which theoretically can be as high as 10 hours, if using a quality hi-capacity cell (e.g. Eneloop XX or Sanyo 2700mAh), but practically I’d say it’ll do 8 hours with a efficient, high-quality driver and 5-6 hours with a mediocre one.
At 120mA, Vf of modern high-efficiency LED (e.g. XP-G2) is close to 2.5V, and nowhere near as high as 3.6V. Also, voltage of high-quality NiMH at drain so low is closer to 1.25V than 1.2V.
10 hours at 40 lumens? Probably emitter lumens measured until the light output was at 3%.
2 hours at 35 lumens? Probably OTF lumens measured until output was at 50%.
What you need at this point is to find someone who’s tested and measured both lights so that you can compare their results. This way the only variable is the light itself and not the tester’s limits or equipment limitations.
Man, that little shopping cart is too cool 
Kind of epitomizes this place. Good one!
Keith (who needs to go shopping)