Dereelight current draw

[torchfreak]

Recently purchased a Dereelight Javelin w extension tube, also a C2H.

I was comparing current draw between the Javelin and C2H, which turned out to be near enough to identical.
What was interesting was the comparison of current draw with the Javelin head with; 1 Li-ion 14500 vs 1, 2 & 3 AA NiMh.

These are the Wh numbers I got by multiplying the rated cell voltages (3.7 & 1.2) with the Ah readings.

---------- 14500 ----- 1 X AA ---- 2 X AA ----3 X AA
High ----- 4.14 --------1.68 ------- 5.28 -------4.14
Medium - 2.44 -------- 1.44 ------- 3.00 ------ 2.40
Low ----- 0.39--------- 0.54 ------- 0.48 ------ 0.40

What confuses me... (not hard - just ask anyone who knows me :duh2 is that the Javelin seems brighter with 3 X AA than with 2 X AA. Yet the Power draw with 3 X AA is lower!
Might there somehow be an efficiency gain or something?

 

[torchfreak]

Anyone?

Javelin with 2 X NiMh AA draws 2.2A (X 2.4v = 5.28W?)
Javelin with 3 X NiMh AA draws 1.15A (X 3.6v = 4.14W?)

It seems much brighter with 3 X AA, yet is using less power!?!?

Might there be an explanation for this?
Or should I throw away my el-cheapo multimeter?

 

[adam83]

Seems to me that the driver should operate more efficiently with 3.6v input as opposed to 2.4v input while providing greater output. Thus explaining the lower power consumption.

 

[vvs]

Looks like 75% efficiency with boost driver and around 95% or more with buck. XP-G has Vf around 3.4V with 1.2A ~= 4W

 

[torchfreak]

Thanks for that, I didn't know about that stuff.

So I guess boost mode, well, boosts the output when the input voltage is below the Vf. Whilst Buck does the opposite, and if the regulation circuit gets out of the way at a certain voltage - direct drive.

Thank you for aiding my education

 

[kosPap]

man thanks for comfirming my data too...

Dereelight Javelin Single Mode XP-G
Alkalines: 200 Lux – 1.65 Adraw
Ni-Mh: 483Lux - 2.17Adraw
Li-Ion: 680lux - 1.38 A draw

 

[vvs]

It's strange on lux readings - maybe 10x of it ?

 

[kosPap]

my bad...thsi was copied from another post of mine

the figures are lux in my lightbox....

 

[red02]

I'm confused, doesn't Dereelight rate their boost drivers as 1 amp?

 

[torchfreak]

I get: 1.4A @ 1.2V-----2.2A @ 2.4V-----1.15A @ 3.6V-----1.12A @ 3.7V.

This is using the standard 3S Javelin, voltages are the batteries rated. The batteries were fully charged.

Interesting is that medium is rated as 15%, here are my readings on medium in the same order as above:
--------1.2A ----------- 1.27A ------------ 0.67A------------- 0.66A

So the current draw on medium seems to be more than 50% of high. :thinking:

 

[vvs]

Explanation are simple:
1.4A @ 1.2V - because alkalines dramatically loses their charger under heavy load. Their capacity near 3000mAh under low load (tens on miliamps) to 700mAh under 1A. NiMH can run under 1C, but driver should meet both demands - primaries and rechargeables.
2.2A @ 2.4V ~ 25% lost in boost driver
1.15A @ 3.6V & 1.12A @ 3.7V ~ 5% lost in buck driver

Another exmplanation with low current with 1 primary is depleted cell OR high input resistance of driver cirquit, but I'm not sure about the last.