new fenix LD20 Q5

Hi guys. I recently bought a Fenix LD20 Q5 from a reliable ebay fenix reseller and I've noticed that I'm not able to get anywhere near the advertised "2 hour burn time" on turbo mode with a fresh set of batteries.

I'm getting more like 45 minutes to 1 hour and 15 minutes. This is with freshly recharged Duracell Ni-MH 2000mAH batteries at room temperature, light standing on tailcap, being timed with a stop watch.

What gives? Do you think the light is defective?

I suspect the burn times quoted by Fenix were done using higher capacity batteries.

Do you have anything to cool the light down? If not, then the light could be going into thermal protection mode.

Try Sanyo 2700mAh NiMH and a different charger
And I really hope you have used a fan to cool that thing, theres no thermal protection.

Also theres variation in the forward voltage of the led that affects runtime.

Fix state their times are based on 2500mAh NiMH batteries as I recall. You should also take any manufacturers claims with a pinch of salt.

Egsise said:

Try Sanyo 2700mAh NiMH and a different charger
And I really hope you have used a fan to cool that thing, theres no thermal protection.

Also theres variation in the forward voltage of the led that affects runtime.

Click to expand...

Good to know on the L2D, I did not know for sure whetehr it had thermal protection or not.

xtian989 said:

Hi guys. I recently bought a Fenix LD20 Q5 .......

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Congratulations, you will love that light.

Here is a very handy "runtime" thread of many, many flashlights. Look at Post #8 for your LD20 Q5.

https://www.candlepowerforums.com/threads/221108

UK sellers quote 1.5 hours for the L2D Q5 and I get between 1 hour 45 minutes and 1 hour 55 minutes on turbo before a noticeable drop using Panasonic Infinium AA 2100 mAh and Panasonic AA 2600 mAh.

Light reviews gives 1.5 hours for your model using 2000mAh Eneloop:

http://www.light-reviews.com/fenix_ld20/runtime.gif

Here is a thread by 'selfbuilt' who finds 1 hour 10 minutes for the LD20 on turbo using Sanyo Eneloop 2000mAh:

https://www.candlepowerforums.com/threads/214890

This UK seller quotes 1.3 hours on turbo using 2500 mah Ni-mh batteries:

http://www.fenixtorch.co.uk/led_torches/fenix_LD20.html

That is not so far off your values. I think that rechargeable NiMH batteries need a number of charges to 'bed in' and fresh ones will not be quite so performant.

Some values quoted on the Fenix site are here:

http://www.fenixlight.com/product.asp?classid=2&Page=2

The above gives 2.4 hours for the L2D Q5, and the same site quotes 2 hours for the LD20 Q5. Mmmm. The Fenix web values are cack. Poop. Soft and steamy. Clearly someone has been smoking crack. You can't even pull the LED Lensor trick since the Fenix lights are regulated, and when the output drops, it does so fairly dramatically.

Oh yes, one last point. There are variations in cells, and some tests find that Japan made ones last a bit longer than Chinese made ones. And some makes last a bit longer than others. Light reviews gets consistantly long times and he uses Sanyo Eneloop which are consistently good performers though I have not seen detailed tests against other makes.

LeifUK don't forget how Vf affects runtime.

Egsise said:

LeifUK don't forget how Vf affects runtime.

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Voltage feedback I presume. Care to explain. :thinking:

It is odd that UK Fenix sellers quote the sorts of values I and others can get, whereas the Fenix main site quotes much larger values. The cynic says this is due to our stronger consumer laws c.f. China.

It's the leds forward voltage, which affects to how much the driver draws from the battery, it's unique to every led.
For example my Fenix LD10 runs only 20 hours on low with 2000mAh eneloop, but someone elses runs 28 hours with 2000mAh Eneloop.
Good example of the effect of high forward voltage vs low forward voltage.
The leds forward voltage does not affect brightness, only to how much current the driver draws.

I agree that Fenix runtimes are optimistic and made with 2700mAh cells and low forward voltage leds.