Regulation and battery life question

tennisplyr3

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I did a search about this on forums, and I wasn't getting the answer that I was looking for. I was hoping that someone could clear this up for me.

When I was comparing flashlights, I saw that the Preon Revo could run @ 1.5 lumens for 67 hours off a single AAA battery. Looking at the Preon 2, it can run @ 2.2 lumens for 23 hours off 2 x AAA batteries. Comparing the two, it doesn't quite add up. Shouldn't the Preon 2 with the 2 batteries run much longer than the Revo, or does that 0.7 lumen difference in the low modes make that much of a difference in run times? Looking at some details, the Revo is "current regulated," whereas the Preon 2 has PWM. In that case, what's the difference between PWM vs current regulation? And why is there such a huge difference in the run times between the two?

Thanks in advance...
 

Swedpat

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I did a search about this on forums, and I wasn't getting the answer that I was looking for. I was hoping that someone could clear this up for me.

When I was comparing flashlights, I saw that the Preon Revo could run @ 1.5 lumens for 67 hours off a single AAA battery. Looking at the Preon 2, it can run @ 2.2 lumens for 23 hours off 2 x AAA batteries. Comparing the two, it doesn't quite add up. Shouldn't the Preon 2 with the 2 batteries run much longer than the Revo, or does that 0.7 lumen difference in the low modes make that much of a difference in run times? Looking at some details, the Revo is "current regulated," whereas the Preon 2 has PWM. In that case, what's the difference between PWM vs current regulation? And why is there such a huge difference in the run times between the two?

Thanks in advance...

Hi tennisplyr3,

I have no answer to your question but consider it highly justified, I know I earlier asked a similar question in another thread.
 

mdocod

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When dealing with outputs on LEDs in this range from power sources that are not well matched to the intended load, there can be vast differences in the driver efficiency. The lumen difference is not the important part of this equation. Different types of drivers are being used in each flashlight for various reasons. (probably to accomplish other capabilities). It's also possible that runtimes are being calculated differently.

Either the 2AAA unit is far less efficient in the driver or the 1AAA unit has had its' runtime figured based on different qualifiers, or some or a lot of both possibilities.
 
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mcnair55

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I have learnt never to presume anything but ask like you have but sorry I also have no answer to your question.
 

Streamer

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I'm just a newb when it comes to the science of these things (torches)..Let me guess...it has something to do with the efficiency or inefficiency of the driver?? Dunno really.

"OH Divine and Brilliant Torch God...Reflect for a moment,
then throw us down the answer".
 

Wiggle

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I believe the Preon output/runtime on anything other than max are questionable. Check for the reviews to see a detailed runtime plot.
 

tre

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A few things:

1) The Preon Revo has been discontinued so you can't buy one.
2) The Revo uses current regulation which is more efficient than the PWM the Preon 2 uses.
3) The Preon 2 low mode puts out nearly 50% more light than the Revo low mode. This makes a huge difference in run time. Combine the Revo's much lower low mode with the fact that it uses current regulation and you have your answer.
 

ico

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From what i have heard before in a recent question I made. It will depend on the amperes the driver is discharging the battery.

The 2AAA is in a series connection so it means that the capacity is still 800mAh(for eneloop). Using a single AAA the capacity of the battery is still 800mAh. What differs is the voltage which is 1.2 in a single cell and 2.4 in the double cell connected in series. Given the runtime info above. The draw of the revo at 1.5 lumens is 11.94 miliamps while the preon 2 at 2.2lumens is 34.78 miliamps. since both have a 800mAh capacity, 800/11.94= 67 and 800/34.78= 23 (theoretical computation only and not exact)
 

tennisplyr3

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A few things:

1) The Preon Revo has been discontinued so you can't buy one.
2) The Revo uses current regulation which is more efficient than the PWM the Preon 2 uses.
3) The Preon 2 low mode puts out nearly 50% more light than the Revo low mode. This makes a huge difference in run time. Combine the Revo's much lower low mode with the fact that it uses current regulation and you have your answer.

Yeah, I'm aware that I can't buy one. This is what I was getting at though -- why does current regulation produce much better run times over PWM regulated lights? If that's the case, why don't they just make all LED lights current regulated?

From what i have heard before in a recent question I made. It will depend on the amperes the driver is discharging the battery.

The 2AAA is in a series connection so it means that the capacity is still 800mAh(for eneloop). Using a single AAA the capacity of the battery is still 800mAh. What differs is the voltage which is 1.2 in a single cell and 2.4 in the double cell connected in series. Given the runtime info above. The draw of the revo at 1.5 lumens is 11.94 miliamps while the preon 2 at 2.2lumens is 34.78 miliamps. since both have a 800mAh capacity, 800/11.94= 67 and 800/34.78= 23 (theoretical computation only and not exact)

This makes me *really* curious about the regulation of the light. Why is it that 50% more lumens translate to nearly 3 times the current draw? Since our eyes detect brightness on a logarithmic scale, isn't trying to detect the difference between 1.5 and 2.2 lumens not worth a 3x increase in current draw? I'd gladly sacrifice 0.7 lumens of difference for 3x the run time.

Thanks for the replies; I'm just trying to better understand these lights. Anyone else have any input to this? :)
 

tennisplyr3

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bump... was wondering about this -- Why does current regulation produce much better run times over PWM regulated lights? If that's the case, why don't they just make all LED lights current regulated? Also, why is it that 50% more lumens translate to nearly 3 times the current draw? Since our eyes detect brightness on a logarithmic scale, isn't trying to detect the difference between 1.5 and 2.2 lumens not worth a 3x increase in current draw?

Anyone? :)
 

Gregozedobe

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I'll throw another three issues for consideration -

1 Not all "lumens" are equal. Until recently there wasn't an accepted standard for measuring "lumens", but now there is a generally accepted standard. This new standard is a bit more stringent and specified in some detail. Generally lights measured according to the new standard are rated at less lumens than they used to be (despite producing exactly the same amount of light as before).

The best way of comaparing light outputs is to look at one of the reputable reviews here on CPF where the output is directly measured by the same equipment for both lights. Comparing both lights yourself is much less accurate, as our eyes and brains are notoriously inaccurate for measuring light output, and depending on beam pattern a light with less lumens may seem brighter (due to a more intense hot spot).

So when looking at manufacturer specs for lumens you also need to find out what standard (if any) was used when measuring. Some of the cheaper lights on eBay are not measured at all, but "rated" as the maximum possible output for a good example of the type of LED used, without any allowance for light lost at reflectors and the glass lens. So the measured ouput can be as little as 40% of what the seller is claiming.

2 Different drivers have different efficiencies (ie how much current the driver uses vs how much current is actually delivered to the LED). Some drivers actually use more current than the LED at low light levels.

3 To truly compare output and run times you need to look at whether the output (lumens) declines over time (this is what happens with many lights that aren't current regulated, whether they use PWM or not). So a non-current-regulated light might put out 2.5 lumens with a fresh battery initially, then drop to 2.0 lumens after 10 hours, then decline to 1.5 lumens for another 15 hours, then decay to less than 0.5 lumens and less for the next 10 hours. The best way to see this effect is in the run-time graphs as seen in many of the light reviews on CPF.
 
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tennisplyr3

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Jan 5, 2008
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I'll throw another three issues for consideration -

1 Not all "lumens" are equal. Until recently there wasn't an accepted standard for measuring "lumens", but now there is a generally accepted standard. This new standard is a bit more stringent and specified in some detail. Generally lights measured according to the new standard are rated at less lumens than they used to be (despite producing exactly the same amount of light as before).

The best way of comaparing light outputs is to look at one of the reputable reviews here on CPF where the output is directly measured by the same equipment for both lights. Comparing both lights yourself is much less accurate, as our eyes and brains are notoriously inaccurate for measuring light output, and depending on beam pattern a light with less lumens may seem brighter (due to a more intense hot spot).

So when looking at manufacturer specs for lumens you also need to find out what standard (if any) was used when measuring. Some of the cheaper lights on eBay are not measured at all, but "rated" as the maximum possible output for a good example of the type of LED used, without any allowance for light lost at reflectors and the glass lens. So the measured ouput can be as little as 40% of what the seller is claiming.

2 Different drivers have different efficiencies (ie how much current the driver uses vs how much current is actually delivered to the LED). Some drivers actually use more current than the LED at low light levels.

3 To truly compare output and run times you need to look at whether the output (lumens) declines over time (this is what happens with many lights that aren't current regulated, whether they use PWM or not). So a non-current-regulated light might put out 2.5 lumens with a fresh battery initially, then drop to 2.0 lumens after 10 hours, then decline to 1.5 lumens for another 15 hours, then decay to less than 0.5 lumens and less for the next 10 hours. The best way to see this effect is in the run-time graphs as seen in many of the light reviews on CPF.

Thank you for the issues for consideration. I'm still curious though since I haven't gotten a straight answer yet.

Why does current regulation produce much better run times over PWM regulated lights? If that's the case, why don't they just make all LED lights current regulated?
 
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