Average internal resistance looks slightly below 25mΩ, just a gnat's ass higher than that of a LiitoKala 26650-50A. Definitively an improvement in energy density, with an actual power delivery rating. Verrry good!
About the fuse, a bit sensitive I'd say. Temperature monitoring definitively recommended/advisable.
Cheers ^:)
Originally posted on Mon, 04/24/2017 - 01:33; IR estimation fixed, content added and make upped.
The shockli would perform better over time because of its higher capacity, not because of a lower IR. At a given resting voltage, like fully charged at 4.2V for example, the cell with the lower IR will provide more current in a direct drive situation, but a cell with a lower capacity will drop its resting voltage quicker over time.
It seems like a compromise between IR and capacity oftentimes. The VTC5A would give more amps at start than this shockli, but obviously the capacity is in a different ballpark and would not be as suitable in a high power light.
Here's the 5A comparison below. So accept for the first 0.25 discharge, the Shockli performs better - the blue line is clearly well above the red line. I though it should produce higher amps in a DD/FET mod, accept for the first 250 mAh. Am I reading this right? Does that first small advantage for the LK mean it will have a lower internal resistance?
The internal resistance is measure at 15A (if the cell can deliver that), but higher voltage at the desired current is always a better metric to look at.
If we are to substract the 20A from the 1A curves, we attain a dV/Ah one which reveals the average internal cell voltage drop for that 19A rate. This reveals close effective average internal resistance. Both first and last parts of the curve shouldn't be used, as there usually steep slope shifts happen because of dramatic changes in the cell's available energy and internal resistance.
The shockli maintains a higher voltage at a given point in the discharge, but that doesn’t mean its IR is lower. The IR determines how much the battery will drop its voltage (the resting voltage minus the voltage under load) at a given current. At a given point in the discharge curve the shockli will have a higher resting voltage than the LK because its capacity is larger, so even if the shockli drops a bit more voltage than the LK the voltage under load will still be higher than the LK because the shockli started at a higher resting voltage.
Essentially the vertical spacing between the discharge curves at different currents is proportional to the IR. In this case the shockli and LK cells have very similar IRs so the shockli’s extra capacity gives it the advantage in pretty much all applications. Comparing the Sanyo 20700A and B cells is more illustrative. At the 5A rate the higher capacity B cell maintains a higher voltage for most of the discharge, but at the 20A rate the lower IR A cell pulls away and is the more suitable cell.
What is the purpose of such 60A test? That is discharging the cell in a quite stressful trial, about equivalent to start discharging the cell with a load of about twice the cell's internal resistance for most of those, with quick load resistance tapering off.
He doesn't uses 4 terminal holders for accurate voltage monitoring, so some current proportional drop should be substracted from added to the curves, at least this is what he told me on another cell review discussion.
Originally posted on Fri, 05/05/2017 - 02:34; lil fixup.
I have so many batteries that have “60A” printed on the wrapper, I was curious as to how batteries would actually perform at 60A. This one charged up ok after discharging at 60A, so I suspect it has a temperature interupt device rather than a current interrupt device.
I wouldn’t go by the results from a West Mountain Radio CBA. I have three of them, but only use them for continuous current testing on NiMh batteries and ICR Li-Ion batteries up to 5A. The slew rate is far too slow for high current testing.
There's a little voltage difference among those curves, likely caused by the associated current travel path resistance to Mooch's voltage monitoring probes. Addressed by me in his review of it.
With regards to the actual limitations of the West Mountain Radio CBA, I have no idea besides knowing Mooch's setup is highly customized and improved.
Oh! By the way, 3.2V as high discharge cutoff? This is something I've somewhat got used to hearing from the E-CigaretteForum (LoL!). In my opinion, it is a very high and inadequate value, though of course I can understand its purpose.
There's no doubt their perspective/approach in all of this battery management stuff is quite different from mine. I always (or nearly) keep my li-ions at a max voltage of 14/15 charge voltage to maximize cell lifespan. Knowing how stressful is discharging a cell at around its effective limits/ratings, my philosophy tells me it is wiser to discharge at a slightly slimmer ratio (divide max by √2 as P = I²R) in order to substantially reduce thermal stress in continuous discharge. For pulse discharging, I'd limit myself to about the continuous rating or very little more.
P.S.: yes, the ANR26650M1-B is a real high discharge champion. Good offers for it in AliExpress.