You think it fully charges the cell then starts to discharge it? Possible I guess.
You would need to remove the cell after charging and maybe use a DMM to check voltage. I suppose it should be at 4.20 to 4.18. Then let the cell sit several hours and see if the voltage drops a little or a lot.
The capacity for that 30Q seems fine so it’s probably not reading high. That’s odd, I thought the PLB-55A cell was the highest capacity at about 5750mah. Interesting.
That wouldn’t be a good design, period, but other people are not reporting this issue with this charger, so it’s possible that there’s something wrong with either the charger or just bay #1. When I made the first post, I was mostly reporting on the currently-shipping Lii-50A capacity, but while cropping the photo I noticed the 3.96V reading and began wondering. Now I have a mystery to solve, though I didn’t want one .
Zeroair does get over 3000mAh, but only at 250mA. I don't have many li-ion cells to choose from, but this one makes a good test case as it's a known quantity and Samsung has very high consistency with them. The above tests were done 3.5 years apart, but the shapes of the curves are largely identical. The 2019 cells do seem to have somewhat higher capacity at low currents, but this could be an artifact of different test environments.
I cannot agree. Take a look at HKJ's 30Q test. Bear also in mind that final cell voltage (which depends of maximum charge voltage, path resistance and cut-off current) affects the capacity measurement, along with cut-off voltage and discharge rate. In my experience maximum charge voltage varies between charger slots, at least in my Lii-500 does.
That’s too strange. I never encountered a Samsung Q-cell to test under it’s specs. Cells tested: dozens of 13q, 15q, 20q. Tester used: Opus C3100 v2.1.
on aliexpress i see sellers of these sells with tons of positive feedback but in the photos, i see various mOhm reading. 24-70mOhm @500-1000mA. not sure what to make of it. i need 5 cells in series. do i buy a set and hope for best of matching mOhm? or should i get something else?
Analyzing chargers do not measure the DC internal resistance of cells, they measure 1KHz AC internal resistance as far as I understand. Additionally, the problem is they measure “at the circuit board”, this means they are measuring battery plus contacts plus rail resistances. Bear in mind that rail and contact resistances are of similar order of magnitude to a cell's internal resistance, and wildly variable at the hands of uninformed, couldknowbetter or careless users.
I will correct myself then: I think the Lii-500 does not measure DC internal resistance. I know this because of a self-made extended cell capacity test in which I ensured minimization of rail and contact resistances before each discharge cycle. Check my Lii-500's internal resistance values for that test here: KingWei 18350 1000mAh 900mAh test.
Why do I know the 51 - 69mΩ displayed values are spurious? Because I later measured each cell's DC internal resistance by injecting DC current into them with my precision power supply, recording corresponding changes in cell terminal voltage and using those figures to obtain true DC internal resistance. I obtained a consistent average of ≈110mΩ. Two cells scored a 104ish - 105ish mΩ minimum while another a 116ish - 117ish mΩ maximum; they came packed up in pairs with a plastic wrap.
Henrik I must say I do not see how chargers, as a whole, use direct current internal resistance measurement. I've seen a lot of figures from different chargers here and there and I do not feel like they are doing that.
It is not a question about feeling, but about circuit. Doing a DC measurement is fairly easy for a analyzing charger, it just need to measure voltage, turn current on and measure voltage again, then do a bit of math. AC requires a lot of extra circuit.
The precision of chargers is usual not very good, due to contact resistance and cheap implementations.
Thanks for pinpointing correction Henrik. The reason I ended up believing “they must be using an AC method” was because of the large divergence between my proven good DC internal resistance measurement method and those provided by the charger even if rail burdened.
Conclusion: cheap chargers measure internal resistance very poorly.
There is also the detail that different measurement methods will give different result, maybe I need to do some more writing about resistance measurements.
The ones that don't turn inside out when you charge them… Is this serious? I know I can turn inside out a t-shirt, for example, but what 26650 cells turn inside out when you charge them?
Yes totally serious some of the substandard 18650 & 26650 cells can explode, they cant handle high C drain or fast charge because they have small Lipo poly cells inside full size cases.