Skilhunt E3A (AAA twisty) - First Look

I agree, when the light gets dim, change the battery

there is No reason to attempt to draw an Eneloop down to 0 volts, and I dont think it is possible in a flashlight, since they stop working around 0.8v anyway.

There was a report recently, that a Sofirn C01 can draw the cell down to 0.4v, IF the light is left ON… but if the light gets turned off, it wont turn back on unless voltage is at least 0.8v…

I see no reason to abuse an eneloop this way. If you really want to run a light at super dim, relatively useless brightness, just cause you like to count (uselessly dim sublumen) runtime… then use an Alkaleak…

I once had a meeting with a few Eneloop engineers (at the Panasonic office in Belgium) , and they said that deep discharge is worse than overcharge.

Here are the questions and answers: https://eneloop101.com/interview-with-eneloop-technicians/

Especially Question #16 onward

Hey, thanks, Lucky!

Yeah, that’s what I do. I’ve never had enough light output when the cells approached 0.8V and so was forced to recharge them. So, I’ll continue to not worry about it.

Thanks to you, too, ChibiM!

:beer:

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

.

now thats Real World :slight_smile:

;) They didn't back up their claims, but I trust they know what they were talking about :D

Thanks ChibiM! I looked on your website before my long post above for any additional information, but I missed finding the interview. I don’t think it is linked in any of your menus.

I think what they noted about overdischarge is still consistent with what is in the Energizer datasheet. The Eneloop engineers state there should be minimal difference between 0.8V and 0.9V, but clearly at some point, overdischarge does become an acute problem.

Interesting, the IEC61951 cycle test actually over-charges the cell every single cycle (0.25C discharge for 140 minutes followed by 0.25C charge for 190 minutes), so there is evidence right there that the batteries are tolerant of slight overcharge. I guess this is why they’ve continued for so long to sell kits that include cheap dumb chargers, even though they know those are not optimal.

then no reason to worry
1% is a very small number

I forgot about that. There’s probably not many lights that can drain a battery as low as the C01, and even that light dim significantly when it gets that low:

> even that light dim significantly when it gets that low

exactly…
Fenix called that 10 hours of sunlight and 11 hours of “moonlight”
LOL!

I think I got this info mostly from steidlmick at TLF. Maybe parametrek as well. From my experience I got one down to 0.8 V and it had lower capacity afterwards (but not sure if there was another factor).

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.

Well, test #1: I reduced the current sense resistance from 0.43 Ohms to 0.30 Ohms. Output increased 42% but overall efficiency took a crap. Once I do a few more tests I’ll post up some graphs.

Next up: do a couple steps of output reduction

Very interested in reduction data. 50% would be nice I think for this light.

Ok. I just started a roughly 50% run. :+1:

Awesome. What size is that resistor? Looks tiny and close to the boost IC. Not sure if I want to swap that myself. :confused:

It’s a 0603 but I managed to fit a 0805 in there. I have a bigger variety of those. I don’t have any 0603 on hand lower than 620 Ohms.

This ~50% run is using a 1.0 Ohm resistor and is chugging along at 43 lumens. I’ll do at least another run at around 5 lumens. Any other special requests?

Yeh, that’s par for the course with those boost converters. It’s unreal how they need to be “fine-tuned” for a particular output. Coil inductance and resistance and size are huge factors. Beyond a certain total current in a specific component, they start to saturate the core. Lotsa heat and current, but no extra output. Like overcooking an LED ’til it turns blue with too much current.

I’d be curious if and where the bottom falls out on the low current end. Either in stability, ripple, or efficiency. 1-5 lumens might be something to shoot for… For data gathering purposes. :innocent:

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!

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.

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.