Streamlight 4AA ProPolymer overdriven?

I don't own one (yet), but something has been bugging me about this light. According to the runtime graph at flashlightreviews.com, there is about ~4 hours of regulation (rounding up). Assuming we're pulling a reasonable amount of power from alkalines I expect to get ~ 2Ah of power out of each in a straight run. 4 batteries at 2 Ah each is 8 Ah of power used in less than 4 hours.. This puts power consumption at over 2 watts. Now, a low Vf Luxeon III, lets say 3.3 v @ 700 ma is just over 2 watts of power where a Luxeon I 3.3 v @ 350 ma is just over 1 watt. So either the circuit is 50% efficient or this LED seems to be way over driven, closer to Luxeon III stock currents. Given the good regulation, I don't think this light has efficiency that poor. I believe my math is correct...

Those who own them.. Has anyone taken the lamp assembly apart? Does the light use a luxeon star (replaceable?) or just an emitter? Would it be hard to swap in a Lux III star of one's choosing?

Edit: To specify 4AA ProPolymer.

1,5 V x 4 = 6 V
6 V x 2 Ah = 12 Wh
12 Wh / 3 W = 4h

don't forget that You need about 4 V for Luxeon and driver overhead and not only 1,5 V from one cell, so use VxAh = Wh (Watthours)

Considering the amazing brightness of this unit, and considering their previous track record of overrunning the 7 LED model, I wouldn't be surprised one bit. I just hope they replace the Luxeons when they start to poop out.

Greg

I was on a battery manufacturer's website a year ago. IIRC at 400mA the power available drops to 1300 mAh or 1.3 Ah instead of the 2AH of your calculation. Also with the batteries in series the watt-hours go up but the amp-hours stay the same. Can't find the link to the data sheet at this time.
For 1 battery 1.3Ah*1.5V=1.95watt-hours
For 4 batteries 1.3Ah*6V=7.8watt-hours
7.8Wh/4h=1.95W provided by the batteries.
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1.3Ah/4h=0.325A or 325A. (norminal drive current of lux 1 is 350mA) Within spec.
0.325A*3.6V=1.17W. (current Lux 1 is actually 1.2 to 1.5W) Within spec.
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The regulation circuit has to absorb the difference in voltage between the battery voltage and the led voltage. 6V-3.6V=2.4V
0.325A*2.4V=0.78W
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Due to failures of the 7led model, flashlight reviews was concerned enough to do addition testing summarised below:

The one concern I did have with this light surrounds driving LEDs at fairly high rates inside a plastic body. Despite the use of a lot of metal in the lamp assembly to draw heat away from the LED, there is nowhere for that heat to go inside a plastic light. As a result heat could have build up caused damage to the LED. Based upon thermal observations, it does not appear that the LED or the surrounding structure get any where near the manufacturer recommended maximum temperature despite continuous on-time.
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I believe Streamlight has a lifetime garuntee on their lights. Check the warrenty info on their website. If the emitter burns out send the light back for replacement. Get a RGA# first.

Last time I measured the current it draws from the batteries, it was 0.5A. I found this a bit surprising, because I expected the regulator to be some kind of step-down converter. Step-down converters generally draw less current (average) from the input side than they provide on the output, while linear regulators draw about the same from the input as they provide on the output.

The conclusion I draw is that the SL4PP uses a linear regulator and that indeed it overdrives the LED a bit.
On the other hand my multimeter might be a bit dodgy, so feel free to repeat the experiment.

I got:

Vin

4.50v 580 mA 2.61 watts
5.00v 510 mA 2.55 watts
6.00v 470 mA 2.82 watts

It would have been useful to have relative lux readings to go with, but there you have it. Almost certainly the LED is being driven quite a bit harder than 1 watt, probably pretty close to 2 watts.

I have one of these lights and love it. I have to admit though , I don't have a clue what you guys are talking about. :huh2:

Greg said:

Considering the amazing brightness of this unit, and considering their previous track record of overrunning the 7 LED model, I wouldn't be surprised one bit. I just hope they replace the Luxeons when they start to poop out.

Greg

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I believe flashlightreview.com actually measured the temperature of the emitter, and found it within Luxeon specs for heat. It does heat up (I can't recall the numbers) but it doesn't *overheat*.

And I believe the earlier 7 5mm LED models did badly overdrive the LEDs, but at some point later on, SL decreased the current to a more reasonable level. At least that's what I recall reading.

Last time I measured the current it draws from the batteries, it was 0.5A. I found this a bit surprising, because I expected the regulator to be some kind of step-down converter. Step-down converters generally draw less current (average) from the input side than they provide on the output, while linear regulators draw about the same from the input as they provide on the output.

The conclusion I draw is that the SL4PP uses a linear regulator and that indeed it overdrives the LED a bit.
On the other hand my multimeter might be a bit dodgy, so feel free to repeat the experiment.

Click to expand...

I don't think that is the case given some of the other measurements posted. The current drawn from the batteries increases over time as voltage sags, suggesting that it might be a step down as you first suspected. At least the plot at flashlightreviews suggests the output is pretty flat, with the current changing it wouldn't be a linear regulator. Perhaps the other poster's measurements were wrong.

I think it's okay to overdrive a Lux I to those levels if you provide adaquate cooling. I just thought it was interesting they seem to be driving it near Lux III levels. If they have a reasonably efficient step down regulator it's within reason to suggest that they are running the LED at ~650 mA, give or take. I guess this, is ultimately the question.

jbay said:

I have one of these lights and love it. I have to admit though , I don't have a clue what you guys are talking about. :huh2:

Click to expand...

AMEN!!:laughing:

webley445 said:

AMEN!!:laughing:

Click to expand...

Well, compare the runtime to the similarly regulated River Rock lantern that uses a comparable LED, housing, and batteries. It's half, I simply suspected that they are driving the LED extra hard. Since I don't own one yet I shared my observations in a more technical manner, and we've had a few people share some interesting tidbits on their lights.

I'm curious as I'm thinking about ordering one and I'm sifting through these details.

I usually don't do calculations based on alkaline batteries; the real capacity is too dependent upon current draw even for a reasonable approximation to be made. Experiments using NiMH or lithium batteries would be a better basis for calculations.

asdalton said:

I usually don't do calculations based on alkaline batteries; the real capacity is too dependent upon current draw even for a reasonable approximation to be made. Experiments using NiMH or lithium batteries would be a better basis for calculations.

Click to expand...

I dunno, if anyone wants to measure the current to the LED, the question would be quite answered without runtimes.