I have two of the “Olight Universal Chargers” and also the similar magnetic USB charger from “Foursevens”.
My Olights terminate charging at about 4.25 V for Li-ion, leaving the battery at about 4.23 V when I measure it a few minutes later. My Foursevens terminates charging at about 4.30 V for Li-ion, leaving the battery at about 4.28 V a few minutes later. I would prefer if they terminated charging at 4.20 V or below.
With NiMH, the charged battery capacity as determined from a discharge test on an analyzing charger is less than what I obtain from charging the same battery on the analyzing charger, but this does not concern me compared to the elevated termination voltages when charging Li-ion batteries.
Yeah, I would definitely not charge LiIon to anything above 4.20V, maybe even stop at 4.10V. Costs barely any capacity, helps a lot with longevity.
Was considering, opted against it since I want to keep it as small as possible for now, and the whole powerbank feature does not (reasonably) work with more than 1 cell. A fixed charger for 14500 only, doing 2x500 mA, not powerbank capable, would however be possible at a later moment.
Current plan: Keep the “core” fixed, and make detachable “modules” that come with 18350, 18650, 14500 and magnetic leads, so the user can choose. Also makes it easier for me to prototype (can just do 18350 only for now), as additional battery board options do not need any significant prototyping. Plug and play.
Battery type should not matter for charge termination voltage, cheap multimeters can have quite big accuracy tolerances though - and so does cheap electronics like those chargers probably are. Hard to pinpoint without one device (be it a voltage source or a multimeter) that is known to be accurate to cross-check.
I collect meters as well as flashlights. The ones I use compare favorably with my Fluke 77 which was checked for calibration by Fluke a few years after I purchased it and which I only use for checking other meters.
I purchased the two Olights four years ago from AmazonUS and the Foursevens recently and also from AmazonUS since the Olight was unavailable.
Even using various power sources and various battery types or brands, my particular magnetic USB chargers consistently overcharge Li-ion and undercharge NiMH.
You may be lucky in that your particular Olight terminates Li-ion at 4.15 V or maybe I am just unlucky with my three chargers, but hopefully results from other forum members (if they can post them) will let us know.
Magnetic leads have issues with button tops sometimes. I don’t have any suggestions on how to fix that… Just bringing it up lol
It’s not convenient and I’m not saying to do this because there’s definitely better ideas, just throwing stuff out there. For my diy battery charger/dischargers holders I make a clamp sort of thing out of whatever I have lying around. Like, I have one made out of a car cell phone holder like this one.
That type of thing. And then I’ll put a screw or a nut or something on the bolt so I can open and close it quickly with a little electric screwdriver
Margin of error at 4.200V on one of those, according to the first datasheet I found for one, I think works out to be between 4.156 V and 4.244 V when calibrated
Really cool would be a small OLED screen or something for voltage, capacity and so on (would be relatively easy since an MCU is already on the PCB) and at least two buttons (for charge current and screen)
For RGB fading I would recommend following steps:
red blinking: empty or almost empty (under 20 %)
red: 20-50 %
orange: 50-80 %
yellow: 80-100 %
green: 100 % (full)
I think, a classic sliding mechanism is essential for such a charger (I know, it is more complicated to build). I mean, what’s the point of such a travel charger if I always end up having to make sure I’ve packed this 14500 adapter too? The point is that I only need the charger and nothing else. Otherwise I could skip this charger and simply choose a light with built-in USB charging or with USB-C-Li Ion battery…
A good and robust housing is also essential for this. I would keep the design as simple as possible, and as elegant as possible - no martial or special design like most other chargers on the market…
This could be solved by some sort of light bar with some RGB LEDs behind it. So color blind people can see if the bar is full or not, and those who can see colors can check easily with color how the charge process is.
Oh yes, pretty colours are not mutually exclusive with accessible designs. More IOs might need to be used (unless the design uses addressable LEDs) as each RGB indicator can be replaced with three monochromatic ones.
Oh no, no, not at all. Shot’s being taken at the way the brass stud in my D4V2 absolutely hammers the flat-tops concave, rendering them unusable with magnetic charger leads.
I’m really interested, but not having 21700 support would be close to being a dealbreaker for serious actual ‘live’ use for me, I don’t use that many 18650 lights compared to 21700. Maybe a separate version that goes up to 18650 and one that goes up to 21700 or 26800?
I’d definitely buy a 21700 one, while 18650-only would be a lot more price-sensitive as I’d more be doing it to support a cool project and have something to hack on than to actually use much.
Also, some kind of method of securing a battery in the charger (like the Xtar SC1 Plus, but better as that strap comes off way too easily).
4.24V is kind of scarily high. Fine if you use the battery right after but bad if you let it sit.
Maybe if it terminated at 4.15V indicated? Good enough for travel.
Although, the beauty of open source - I’d make mine terminate there anyway, but ideally, it should include some kind of user calibration option - that way the user can use a multimeter to tune it if they want to charge as high as possible without overcharging.
That is an excellent point I did not think about. Thank you! Will make it 4 LEDs.
Yeah, I think that’s what I will do. Colors have the advantage you can see them from across the room, and making it a bar will make it accessible for color blind.
That is my plan, they are usually not particularly power efficient, but on a charger with USB input, whether the LEDs waste 5 mA does not matter. I’m usually designing wireless hardware running nRF52840 chips, and when your idle draw is double-digit uA range, adressable LEDs and their quiescent current are a major issue.
Not to mention they cut out when you shake the flashlight. I hate brass button terminals.
For 21700s xtar has a pretty fancy single-cell USB-C charger with powerbank feature, I won’t focus this one around big cells. Original design goal was only for 14500 and 18350 as those are my primary EDCs, extended upwards later when I figured I could make it community-oriented.
If I stick to my design idea of making it modular, a 21700 version is definitely viable though.
Most of the better quality integrated LiIon chargers do not use external sensing circuitry, and the easier-to-use ones have no adjustable charge termination voltage. For MAX77757 for example you have different chips that terminate at different voltages, and they only seem to have 3.6V (LiFePo), 4.2V, and then 0.05V steps up to 4.45V (wtf??). At least they seem to be set up with tight tolerances, so won’t randomly go ±10%.
Maybe I will go one device class higher and pick a i2c configurable chip, but that will put me way over my head in programming - my skills are good enough for a simple UI with some LEDs, and setting some pins high/low to switch between different current selection resistors, but configuring a complex chip via i2c… Oof.
On the other hand, for my planned powerbank project (different topic, personal project for a 4x21700 or 8x18650 65W PD capable powerbank) I will have 2 separate MCUs and 2 i2c chips to communicate, so gotta learn eventually anyway
I currently do not have a whole lot of time on my hands, so can not promise this project will progress quickly, but your inputs gave (and will continue to give) me some valuable ideas for improvements and changes - thanks at that point! I’ll see what exactly is viable to implement and what isn’t, and try to come up with a new feature list, as well as a new mock-up of my updated design idea when I find the time.
Maybe it will end up versatile and good enough that it will turn into a viable-for-everyone allrounder.
I am guilty of that… when I need a fresh battery I take one out of my spares box
I then charge the depleted cell and put it in the spares box
I use the Olight Universal charger, which on My DMM cuts off at 4.15V, but apparently my DMM could be reporting low and actually cutting off at 4.24V
so, what is Scary Bad about putting away a fully charged battery, that might sit for a month before I put it into use?
shorter lifetime, reduced runtime capacity, or other more dangerous risk?
fwiw, when I check voltage using two of my TS10, they blink 3.9V, when my DMM says 3.87V… so I dont know if my particular Olight charger is overcharging by 0.03V, or the TS10 are just rounding up… (I did not change the voltage calibration on the TS10 lights, they are just factory stock)
or, when I measure a freshly charged 14500 at 4.15V, my TS10 lights will show 4.2V, but when my DMM reads 4.09V, my TS10 lights report 4.1V…
Should I worry that my Olight charger is overcharging, and my DMM is reading dangerously low?
Some random thoughts in no particular order.
The charge rate recommendation is over a large temperature range. My feeling is if you are in the 60-70° F (15-22C) range most of the time you can exceed the recommendation to some extent. As long as the batteries are not getting excessively warm. No more than 20° f rise above ambient temperature. And I suppose that 20° rise is really over any ambient temperature. But certainly when you’re at the low or high end slower is better.
Just because a charger is rated for one amp doesn’t mean it’s going to always try to put one amp into your 14500 battery.
I don’t like to drop voltage in a battery down below 3.5 or much above 4 volts.
Cell phones are able to charge pretty damn fast today but some of them will give you the option to limit the high end to 80 or 85% . Most EVs do that also although some go up to 90%. And they both do that to extend the batteries useful life. But they still allow some pretty damn fast charging in the middle from 30 to 80%. Phones and EVS have more protection built in monitoring temperature and other things.
So stay away from the extremes on temperature and voltage and I think you can get away with faster charging. Don’t charge loose batteries unattended.
My primary charger for many years has been 2 Folomov A1 magnetic chargers with 2 USB detectors so I can check the amps periodically. When it gets down to 0.3-0.5 amps I know I’m usually around 4 volts and I stop. So not long after the constant current phase is done.
I always use one of the USB detector/ testers on flashlights with built-in charging also. The Folomov is no longer made but is very similar to the trustfire mentioned above or another A10 magnetic charger that’s available. I’ve got a few of the a10s and they work okay but two of them bit the dust after 6 months to a year.
So without being able to check amps I would not find a little charger like this useful.
Cells degrade faster as the voltage increases so the higher the voltage when being stored the shorter the overall life of the cell will be. Not by a lot, but if cell life is a priority then storing at a lower voltage will help.
Most li-ion (that includes LiPo) cells are rated to 4.25V so IMO 4.24V isn’t dangerous (if that reading is accurate) but it sure isn’t good for the cell.
Just taking a shot at button tops out of nowhere??
