Driver efficiency tests

ZoomieFan · 2018-06-08T06:51:39.000Z

The following is absolutely no stab in the back of all the great cell testers on this forum. I respect all of them. In fact without reading a test I won’t buy a cell.

A lot of tests of cells on this forum. If those tests are (very) good, I’m sure many pay a small premium for them.
But why? Very often because a few percent more juice means a little longer runtime.

All very useful, but what I’m missing is tests of drivers.
A efficient driver may make a bigger difference in runtime than a cell that packs a few mAh extra.

I’m not just talking about drivers that are sold separately (by members) but also those part of flashlights.
Yeah, many flashlight reviews have runtime graphs which are a good indication. But no more that that because quality of cells may vary.

What to test?
Remove the cells and hook up a power supply. Let it run for 30 mins and write down the watts used. Also measure the lumens. Combined that would give a lumen/watt rating.
That’s useful for testing the overall efficiency of the flashlight. Surely an important number for me personally.
But it doesn’t really test the driver because the efficiency of the LED influences the numbers.
The only way I see to resolve that is by also measuring the watts delivered to the LED.

That sort of info is useful for people that just buy and use. But also for people who consider swapping components. The tests may show that certain swaps will be a downgrade.

Please discuss!

kiriba-ru · 2018-06-08T07:25:59.000Z

Bad idea. Efficiency always depends from input voltage which is not fixed with cell powered lights.
Also, efficiency is not something that you can simply use for any calculations. If you have 1x18650 light and X 7135 chips driver you can calculate how long will it run with 10% or 40% or 100% and this rough calculations will be enough precision for real life usage. If you have bigger light with more complicated driver and various features like thermal regulation or ramping, any efficiency number would not help you to estimate lumens to hours ratio.

Pezo · 2018-06-08T07:47:54.000Z

You could still measure the efficiency of the driver over various input voltages, output voltages, currents, temperatures. You’d get a huge number of measurements for sure, but you could condense them to some key numbers/indicators like “efficient for low brightness”, “not efficient at all” or something else people might think about.
I think it’s a great idea to measure those numbers, but probably a lot more work than most of us would be willing to do, and of limited usefulness.

Agro · 2018-06-08T08:44:21.000Z

kiriba-ru:

Bad idea. Efficiency always depends from input voltage which is not fixed with cell powered lights.
Also, efficiency is not something that you can simply use for any calculations. If you have 1x18650 light and X 7135 chips driver you can calculate how long will it run with 10% or 40% or 100% and this rough calculations will be enough precision for real life usage. If you have bigger light with more complicated driver and various features like thermal regulation or ramping, any efficiency number would not help you to estimate lumens to hours ratio.

Thermal regulation - causes problems, in practice limits tests to short bursts at different input voltages + interpolation.
Ramping - you can measure current, just try several and interpolate again.

Yes, this adds work.

But I love learning about driver efficiencies.

maukka · 2018-06-08T08:52:41.000Z

For a flashlight, the total system efficiency is what matters. That is the emitter, driver, optics/reflector, lenses, wires and contact resistance and the effect of heat on those.

That’s why it is useful to measure the output over time in lumen hours for the complete runtime of the light. Knowing the total battery capacity in watt hours adjusted for different runtimes/current, it’s simple to calculate the lumens per watt which takes into account everything. Or at least approximates it very closely as long as your numbers are accurate.

But since it is rare that a light is used for prolonged periods from full battery to empty, it’s more pertinent to look at the system efficacy at lower levels.

For bare driver tests, HKJ did them in the past: Index of led driver tests

ZoomieFan · 2018-06-08T09:48:48.000Z

maukka:

For a flashlight, the total system efficiency is what matters. That is the emitter, driver, optics/reflector, lenses, wires and contact resistance and the effect of heat on those.

Agreed, and I would love that sort of info in a standardized way. If the reviewers use different cells then total runtime can be misleading.

Say I buy a flashlight that is tested as having good efficiency, but it only has 3 modes and I want 5 modes. I could replace the stock driver with a driver that is extremely configurable. But I doubt I would do so if it turns out the new driver is 20% less efficient.

And yeah, I do understand testing can be difficult when thermal regulation kicks in on those super bright turbo modes.
Personally I need far less brightness. So tests at 300, 600, 1000 lumen would be what I would like to see. Those brightness levels often can be sustained for a long time.
Maybe the flashlight has a 2500lm turbo that steps down after a minute. Because that’s so short I don’t really care about that efficiency.

djozz · 2018-06-08T10:02:51.000Z

I did a few tests on drivers from led4power in the past:

djozz's test of led4power 17mm PWM-less 5A driver Flashlight Modding and DIY Parts

(this will be a limited post for now because I am going away until next wednesday, I will update this post with graphs and such when I have time again) I received led4powers driver in the mail last week and today I had some time for testing. In a PM led4power asked me to change a cap for a different value because preliminary results from HKJ showed oscillations of some kind at certain circumstances. No idea what it was exactly (I know Ohm's law quite well, and not much more than that), but I wa…

LD-2, some testing of two prototypes of led4power's new driver board Flashlight Modding and DIY Parts

[image] Introduction A month ago I received two prototypes of a new flashlight driver from led4power, named LD-2, with the request for testing them, especially the parasitic resistance. I was of course very honoured that I was to test his brand new driver (who am I to know it all about drivers? I don't), but I felt also a bit uncomfortable because testing them well involves the time and dedication more suited for someone retired with a lot of time on his/her hands than me: busy with work, fami…

led4power's LD3 driver, impression and some observations Flashlight Modding and DIY Parts

[image] First I have to apologise to led4power for posting this so late, he has send two of his new drivers to me for review already a month ago, which I really appreciate because I do not see myself as a connaisseur of custom drivers and do not have the electronical knowledge and equipment to do quality testing like HKJ does. I received them a full month ago and it took until now to write a post about it. Reason is that I did have numerous little time-slots to chat in the forum but the past mo…

I like to see a driver tested every now and then to see what its role is in a flashlight, as well as a reflector, a lens, a switch etc. , but I would find it boring to check all that in each and every flashlight, I agree that a total performance of a flashlight is more interesting than just what the driver does.

maukka · 2018-06-08T11:53:17.000Z

djozz:

I did a few tests on drivers from led4power in the past:

Oh, nice tests. Hadn’t seen those before.