Skilhunt E3A (AAA twisty) - First Look

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Scallywag
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jon_slider wrote:
ChibiM wrote:
Especially Question #16 onward
thanks for the interesting story
fwiw, #16 says:
There is no real testing data to prove this point of how much % cycle life at certain voltage is lost etc. but a deep discharge will reduce the cycle life, this can be by 1%, but can be more as well.

so, just FUD and nothing specific

.

Unheard wrote:
I’ve never had enough light output when the cells approached 0.8V

now thats Real World Smile


Considering Panasonic/Sanyo makes 100% of the best NiMh batteries in the world (I’ve experienced this in Prius battery world and cordless tool battery world as well), I think somewhere at the company they definitely know what they are doing. Whether the engineers ChibiM spoke to in Belgium have the data at hand (and/or can share it) is another matter.
roostre wrote:

My wife has lots of decorative string light arrangements and fake candles that automatically light up for eight hours a day which use either two or three AA sized batteries configured in series with no low voltage protection.


We are using NiMH rechargeable batteries and when the lights stop working (besides having very low voltages) usually one of the batteries in series from the “three-battery” lights has also temporarily reversed its voltage.


I have recharged these NiMH batteries about twenty times already without any visually noticeable adverse issues so it has saved us money over using non-rechargeable Alkaline batteries (which unfortunately occasionally leaked) and I am curious to see how long these NiMH batteries will ultimately last under these conditions.  Being an old guy, I am no longer worried about my NiMH batteries not lasting longer than me and hope to outlast them all.


Please let me know if there are any safety issues that I may not be aware of from recharging NiMH batteries that have reversed their voltage.



Also, I purchased two Skilhunt E3A lights (one regular and one high CRI to compare) and while I prefer the compact form factor and exceptional build quality of the E3A, I use my Sofirn C01S light more because of its additional low brightness mode which is especially useful as a passenger in a car or while inside a dwelling after other’s bedtime.


I don’t have sources to cite, but to my knowledge: reversed-polarity NiMh are considered failed. You can sometimes recover them but you’ll have noticeable capacity losses after even just one occurrence. At worst you’re risking them leaking. Leaking NiCd/NiMh cells is hard to do but when it happens the products are unmistakably toxic – I have dealt with them in the battery recycling world.
If you do get any that leak, please dispose of them safely. Probably best not to vacuum the powder as a household vacuum would likely distribute the dust throughout your home.
hodor
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gchart wrote:
Before putting together the graphs, here are a few numbers using NiMH running to 10%:
  • Stock with 0.43 Ohm: 93 “maukka lumens” for 77 minutes
  • Replaced resistor with 1 Ohm: 42 “maukka lumens” for 210 minutes!

Very nice! 30-40 lumens is probably my sweet spot for around the house use. Will need to see what resistors I have lying around.

I recently bought a rainbow of C01s to use as reading lights / for younglings but I’d be also be curious how low it could go while maintaining a stable output.

Tartarus
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gchart wrote:
Before putting together the graphs, here are a few numbers using NiMH running to 10%:
  • Stock with 0.43 Ohm: 93 “maukka lumens” for 77 minutes
  • Replaced resistor with 1 Ohm: 42 “maukka lumens” for 210 minutes!

Thanks for the information and the runtime test. I also did it with a 0603 resistor and changed the lens to a slightly narrower angle. I am very satisfied with the end result.

gchart
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Alright, the low output runtime finally finished so here are the results:

  • The only AAA alkaline I had sitting around was used, but measured at 1.55 volts so fairly full. That said, the runtime is understandably shorter than expected. You can see it held regulation for a little bit, then ramped down out of regulation. Output started out at 95 maukka-calibrated lumens.
  • Using a NiMH (“1100 mAh” EBL LSD NiMH which is actually a 960 mAh cell but still very nice). Output started out at 95 maukka-calibrated lumens and stayed in regulation for 65 minutes.
  • Also on NiMH, but with the output bumped by adding a 1 Ohm resistor in parallel with the stock 0.43 resistor. Output started at 133 lumens and didn’t regulate very well. It dropped hard at 35 minutes. This configuration is not recommended.
  • Also on NiMH, but now using only the 1 Ohm resistor. Output started at 43 lumens and stay in regulation for 185 minutes. This is a good option if you like extended runtime.
  • Also on NiMH, but now using only a 20 Ohm resistor. Not pictured. Output was around 2.3 lumens and ran for 69 hours (3 hours shy of 3 full days)! Efficiency was very good with amazing runtime.
  • On all tests besides the last, I stopped the test when it dropped to around 2 lumens. For all of those, the battery at that point was around 1.1 volts. When I did the 2.3 lumens test, the light actually started blinking (probably the regulator struggling to enable) and voltage was 1.0 volts.

SammysHP
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Fantastic, thank you!

hodor
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Amazing work gchart, thanks for your time and efforts, I’m almost certainly going to get some to mod now.

gchart
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No problem! I’m sure it’s been said somewhere, but just as a reminder: the stock current sense resistor is 0603 sized. I was able to carefully fit a 0805 on there, but if you have 0603 available I’d recommend those.

SammysHP
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The question is: Can you replace it with a 1Ω resistor and a second 1Ω in parallel, but switchable somehow? Big Smile

DonGeron
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Thank you, gchart!
Coming from a non-technical background it’s a bit hard to understand where all the energy went to… In case of alkalines, Duracell Coppertop AAA can deliver 0.5 W constant power for over an hour. Practically every LED light bulb manufacturer reported that their fixtures passed 200 lm/W threshold. Bare LEDs passed that like 8 years ago. So, one hour of regulated 100 lm on one AAA alkaline element should be common place by now, right? From the chart it seems like we get a quarter of that. Where did all the energy go to?

hodor
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Yup, saw your comment about resistor size earlier in this thread. I only have 0805 so will try that first otherwise looks like I’ll be ordering more parts Blushing

gchart
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SammysHP wrote:
The question is: Can you replace it with a 1Ω resistor and a second 1Ω in parallel, but switchable somehow? Big Smile

Not without replacing the driver. This is single mode only with no potential for having two modes.
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DonGeron wrote:
Thank you, gchart!
Coming from a non-technical background it’s a bit hard to understand where all the energy went to… In case of alkalines, Duracell Coppertop AAA can deliver 0.5 W constant power for over an hour. Practically every LED light bulb manufacturer reported that their fixtures passed 200 lm/W threshold. Bare LEDs passed that like 8 years ago. So, one hour of regulated 100 lm on one AAA alkaline element should be common place by now, right? From the chart it seems like we get a quarter of that. Where did all the energy go to?

The higher the current draw, the less apparent capacity. Especially for alkalines. NiMH have better discharge characteristics for higher current draw but there’s still a limit.

In looking at this chart in the Duracell AAA datasheet you linked to…

You can see that as draw goes up, capacity goes down drastically. In stock form, this driver is dialed in for 221 mA current to the LED. With an LED vF around 3.0 volts, that’s 663 mW. There’s some inefficiency… let’s say the boost driver is 85% efficient. That’s a total power draw of 759 mW. According to that chart, it shows to expect around 1/2 hour of service life at those kinds of power draw.

SammysHP
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gchart wrote:
Not without replacing the driver. This is single mode only with no potential for having two modes.

Resistors are small. Solder one in place, attach a second one in parallel with thin enameled wire, with a contact that can be switched somehow. Must be integrated in the plastic holder.
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DonGeron wrote:
… Where did all the energy go to?

There are lots of 80%s in there.

The ’351 is rated about 170lm/W. Optics might have roughly an 80% efficiency (ie, 100lm from the LED = 80lm OTF [out the front]), the boost driver might be 80% efficient, etc. Losses add up.

Also, internal resistance goes up as a cell drains. Terminal voltage drops, to the point where the driver can’t keep supplying current, hence it dims and eventually turns off. The more current you suck out, the lower the terminal voltage.

I just burned down an alkaleak last night supplementing some light when reading. My E03 still had all 3 modes, but M was almost indistinguishable from H. Turned it off to flip through pages. Next time I tried turning it on to read something of interest, it wouldn’t turn on. Left on, it could’ve burned lots longer.

Point being, alkaleaks are pure evil. They do things just to screw with us and cause us misery.

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

DonGeron
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Quote:
According to that chart, it shows to expect around 1/2 hour of service life at those kinds of power draw.

Thank you for the explanation, that’s about the level I can still understand Smile
The LED has efficiency of about 100 lm/W then, right? That accounts for one half of my inflated expectations. So, we should expect 0.5 hour of fully regulated output. We are getting about half of that, if I eyeball it correctly. And we have already factored in driver inefficiencies (85%) and the actual power draw of the LED. What does that mean? The driver is actually 43% efficient? Or the element is not quite Coppertop quality? It feels like we are being shortchanged at every turn Smile
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This is another important piece to keep in mind… I didn’t have any brand-new batteries to test. My alkaline was partially used.

gchart wrote:
The only AAA alkaline I had sitting around was used, but measured at 1.55 volts so fairly full. That said, the runtime is understandably shorter than expected.

Here’s Skilhunt’s chart. It probably pretty close to reality.

And yes… there are inefficiencies everywhere. Increased power draw decreases battery efficiency. The driver has some inefficiency (roughly 85% or so). You’ll lose some through the optic (~15% loss). It all adds up unfortunately.

DonGeron
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gchart wrote:
Increased power draw decreases battery efficiency.
The constant power discharge graph already accounts for that. Right? Falling voltage, rising current – it’s already there. When all is said and done Duracell promises you 750 mW for 0.5 hour = 375 mWh. Or, if you can lower you consumption rate, 500 mW for 1.1 hour = 550 mWh

gchart wrote:
The driver has some inefficiency (roughly 85% or so).
It doesn’t look like like it’s 85%. The LED consumes 221 mA at 3 V = 663 mW while in regulation. Once the light output drops I assume the power used drops proportionately, so I completely unscientifically integrate total power (663 mW * 5 min + 330 mW * 20 min) = 165 mWh. If we assume driver efficiency at 85% it’s 195 mWh out of the battery. So either your battery was half discharged (but then it wouldn’t measure 1.55 V) or the driver efficiency is about 50%.

gchart wrote:
You’ll lose some through the optic (~15% loss).
I know even less about optics than I do about electricity, if that’s possible Smile Let’s ignore that for now.
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Thanks Gchart! Awesome data!

I did some crude and quick tests of my own E3A tonight with stock resistor HiCRI version with a bench supply and my eyeballs.. I’ll likely do it again at a later time with more equipment and effort..

From off (sweep up), turn on voltage on my sample was 920-930mV. Once on, LED didn’t go dark until 0.13V!! I didn’t expect that!

From 1.4V down, I saw min input power at 800mW which increased linearly until about 1.25V ( Peak input wattage happened at 1.03Vin (1160mWin) after which power began dropping quickly. Heres the raw data in Vin mWin. Laptop is dying.. edit later

1.4 0.84
1.35 0.85
1.3 0.87
1.25 0.9
1.2 0.92
1.15 0.97
1.1 1.02
1.07 1.06
1.04 1.1
1.02 1.16
1 1.09
0.97 0.99
0.94 0.89
0.91 0.79
0.85 0.59
0.8 0.46
0.75 0.34
0.7 0.23
0.65 0.14
0.6 0.07

DonGeron
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Or, to put it visually

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Thanks for that, I’m very much a visual person. So in the primary operating range, it appears to range between 800-900 mW. Certainly explains why alkalines really aren’t a great fit and that NiMH & lithium do much better.

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If I’m honest with myself, idk if I’ll get back around to more measurements with this light this week. But I’ll clean up the post and data from my PC tonight. Thanks for posting that plot in the meantime Don.

Gchart, I agree that at stock output, alkaline is only compatible technically. Though in the 2.3 lumen mode and now seeing how far down this boost driver operates, I can imagine some crazy runtimes.. And leak prone cells

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gchart wrote:
Certainly explains why alkalines really aren’t a great fit

Is that to be expected from a $10 flashlight? Or there are no boost drivers with >90% efficiency in 0.8-1.8 Vin range regardless of how much the light costs?
Thinking way back, my Walkman was able to suck two AAs dry in the late 80s, so it should be possible. Maybe not in a flashlight form-factor?
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It’s all about the power draw. That’s just a lot of power to ask of a AAA alkaline. If the output were lowered a bit (like in my 42 lumen test), I imagine the alkaline would respond much better.

DonGeron
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It’s hardly cell’s fault that the driver draws 1160 mW just to pass 663 mW to the LED, is it? It was doing it to the bench supply.

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Took some comparison shots with some of my AAA flashlights. Not enough to open a new thread, hope that’s OK for you.













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oooh, i actually been eyeing the edc01, cant believe its significantly bigger, hm…

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niajef wrote:
oooh, i actually been eyeing the edc01

edc01 (new worm), is a 3 mode light, arguably more versatile, and batteries can last longer

The E3a comes on at a brightness, 90 lumens, that drains an AAA in 30 minutes.. to me, that is a waste.. but its the smallest, lightest, highest CRI aaa option, if someone wants a keyring light for example. I personally choose not enlarge my keyring. My lights are easier for my use, separate from my keys.

the edc01 is rated to go 4 hours on its medium of 30 lumens, plus it has a 5 lumen low, plus a high that matches the E3a.. however, there is NO High CRI edc01 option.

to get High CRI aaa, another option is the aaa Tool from drop.com.. comes in fancy metal too.. $lippery

so, for simplicity, the tiny E3a, with high CRI, is king of the little light Hill

try them all, then decide Cash

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jon_slider wrote:
The E3a comes on at a brightness, 90 lumens, that drains an AAA in 30 minutes.. to me, that is a waste..

But it runs 60 minutes on an AAA. Wink
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SammysHP wrote:
jon_slider wrote:
The E3a comes on at a brightness, 90 lumens, that drains an AAA in 30 minutes.. to me, that is a waste..
But it runs 60 minutes on an AAA. Wink

my mistake, you are actually correct.. E3a are great little lights,
zeroair did a runtime and review

and it did last 60 minutes on an AAA, which is impressive Thumbs Up

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Runtime on these is impressive! I’m flummoxed that the new Skilhunt E2A AA can’t keep up despite more capacity and larger host. Zeroair’s review shows the E2A is stabilized at only about 65 lumens.

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