ConneXion X2 draw & runtimes - does this make sense?

[DHart]

I was surprised that the output on my ConneXion X2 Q5 is substantially lower than my other AA/14500 lights, so I decided to measure the draw with both a 14500 Li-Ion and an Eneloop.

These are the measurements I came up with:

ConneXion X2
with AW 14500 750 mAh cell
Draw ======== Est. Runtime
340 mAh ===== 2.2 hrs. runtime
100 mAh ===== 7.5 hrs. runtime
20 mAh ===== 37.5 hrs. runtime

with Eneloop 1950 mAh cell
Draw ======== Est. Runtime
2A ========= 1 hrs. runtime
830 mAh ===== 2.35 hrs. runtime
170 mAh ===== 11.5 hrs. runtime

Do these numbers look about right?

Is the significant difference in draw between the Li-Ion and the NiMH cells simply due to the voltage difference between them (4.1v vs. 1.3v) or does something look wrong?

Ceiling bounce output measurements are:

14500 Li-Ion
High ==== 3.6 EV
Med ==== 2.0 EV
Lo ==== .1 EV

Eneloop
High ==== 3.4 EV
Med ==== 1.2 EV
Lo ==== - 1.6 EV

 

[rmteo]

Looks like it's drawing twice as much power on the Eneloops compared to the 14500. Is it significantly brighter on the Eneloops?

 

[DHart]

Looks like it's drawing twice as much power on the Eneloops compared to the 14500. Is it significantly brighter on the Eneloops?

Ceiling bounce output measurements are:

14500 Li-Ion
High ==== 3.6 EV
Med ==== 2.0 EV
Lo ==== .1 EV

Eneloop
High ==== 3.4 EV
Med ==== 1.2 EV
Lo ==== - 1.6 EV

 

[rmteo]

The driver/LED combo seems much less efficient at the lower voltages - 14500's would be the way to go with this light IMO.

 

[MorePower]

I was surprised that the output on my ConneXion X2 Q5 is substantially lower than my other AA/14500 lights, so I decided to measure the draw with both a 14500 Li-Ion and an Eneloop.

These are the measurements I came up with:

ConneXion X2
with AW 14500 750 mAh cell
Draw ======== Est. Runtime
340 mAh ===== 2.2 hrs. runtime
100 mAh ===== 7.5 hrs. runtime
20 mAh ===== 37.5 hrs. runtime

with Eneloop 1950 mAh cell
Draw ======== Est. Runtime
2A ========= 1 hrs. runtime
830 mAh ===== 2.35 hrs. runtime
170 mAh ===== 11.5 hrs. runtime

Do these numbers look about right?

I think your current measurements for the Eneloop cell might be off for medium and low modes. Selfbuilt got 7.25 hours on medium (ie. ~270mA draw) with an Eneloop and "4.5+ days" on low with an alkaline cells in his review. Your measurement of 2A on high with an Eneloop looks to be in line with his measured runtime of 59 minutes on high.

Also, your estimated runtimes with AW 14500 cells are likely off by a bit, due to the fact that their actual capacity isn't 750mAh. Again, Selfbuilt got 1.78 hours on high with an AW 14500. If your current draw measurement of 340mA is correct, that equates to a capacity of ~600mAh for AW 14500 cells, which would adjust your medium and low runtimes to 6 hours and 30 hours, respectively.

 

[DHart]

Yeah... my estimated runtimes (not actual measured!) are just calculations based on a presumption of 750 mAh on the 14500, with the understanding that runtimes could well be less due to less cell capacity than 750 mAh.

During the current draw measurement, the DMM is showing a changing range of current at each level, so my numbers are just taken from within those ranges that I saw on the meter...

What I was unsure of is the "normalcy" of a light like this pulling such a different current from the 1.3v NiMH vs. the 4.1v 14500. So I take it that seeing this much of a current difference from Eneloop vs. Li-Ion is as expected, right?

 

[MorePower]

What I was unsure of is the "normalcy" of a light like this pulling such a different current from the 1.3v NiMH vs. the 4.1v 14500. So I take it that seeing this much of a current difference from Eneloop vs. Li-Ion is as expected, right?

Yes, for a light that is regulated on both lithium ion and on NiMH cells you'd expect to see that disparity between currents drawn.

Since your ceiling bounce output numbers on high are fairly similar, you can be pretty confident that the LED sees close to the same power with either type of cell when run on high.

Estimating power drawn from each type of cell on high at initial turn on gives us the following:

14500: 4.1V * 340mA = 1.394W
Eneloop: 1.25V * 2000mA = 2.5W

It's much more efficient to buck a 4.1V source down to the Vf of the LED than it is to boost from 1.25V up to the Vf, so let's assume 95% efficiency for the 14500 and 60% for the Eneloop.

This nets us the following for power to the led with each cell type,

14500: 1.32W
Eneloop: 1.50W

which are really pretty close, even with all the guessing and inaccuracies I've probably included in my calculations.

 

[DHart]

MorePower... thank you for that analysis... it really helps me understand what is going on here "under the hood". :thumbsup: