just a general note, since i tested something similar yesterday:
capacity claims, such as "typ. 700mAh" are a mathematical function f of the 3 main parameters CC, coV and last but not least T: f = f(CC, coV, T)
so before one can compare the spec'ed "700mAh" one needs to ensure that the tester employed 100% exactly the identical parameters which were used to produce the claimed capacity. CC means constant current discharge rate, coV means cut-off voltage, and T means environmental temperature.
Panasonic Co. most often uses the following reciprocal parameters to define the rated capacity of cylindrical li-ion cells:
CC =
0.2C where C is Panasonic-defined not as the typical, nominal or rated capacity but as the minimum capacity (at a given T, 0.2C, and coV)
coV =
2.50V, not 2.75, 2.80 nor 3.00V
T =
25°C, not 20°C
For example the famous NCR18650A cell, which is often called a "3100mAh cell". Try to study and understand its
PDF-datasheet and what i meant with "reciprocal".
at 25°C, min/typ 2950/3100mAh (i.e. C=2950), and 0.2C discharge rate is -590mA, 2.50V cutoff.
at 20°C, no min/typ data is given
Why did Panasonic employ the weird discharge rate of -590mA? Because 2950*0.2 = 590, so C is indeed 2950, not 3100. Point is, you're supposed to test your cell with 590mA discharge rate at 25°C and 2.50V cutoff, and then typically you should get out 3100mAh, and not the 2950mAh on which the discharge rate was originally based upon.
Yesterday i tested the Eagletac CR123A, a "3V 1500mAh" lithium cell. Temperature was close enough to 25°C. Problem: the official parameters are unknown which are to lead to the 1500mAh claim. What's the CC (0.2C?), what's the coV (can't be 2.50V because it's a lithium, not li-ion cell!), what's the T (prolly 25°C)?
With my equipment, i chose the following discharge parameters:
CC = 0.2C = -300mA
coV = 0.8V (that's the lowest possible on my device!)
T = ~25°C
and i got the following result:
[email protected]: 1400mAh
[email protected]: 1511mAh
Once the cell hit the 0.80V, i let it rest for some time and re-run the -300mA load to see if i could squeeze a few more mAh's from the "recovered" cell. Interestingly, CR123A cells don't recover like Alkaline cells do. Once it is fully discharged, it is dead and stays dead. The accumulated capacities are:
1511mAh
1537mAh (1st rerun)
1546mAh (2nd rerun)
1553mAh (3rd rerun)
My point is, with measured 1511mAh i did hit the nominal capacity of "1500mAh". However, i had to discharge the cell down to inhumane 0.80V cutoff voltage. If i had stopped the test run at 1.50V cutoff voltage, i would have measured 1400mAh only!
So back to the Keeppower 16340 cell example:
If the Keeppower discharge parameters for the so-called
standard test were <
25°C, 0.2C, 2.50V > but the battery reviewer used <
20°C, 0.2A, 2.80V >, then you cannot compare the spec'ed 700mAh with the reviewer's measured 615mAh. But you could ask the reviewer (sorry HKJ hehe
) to try to reproduce the 700mAh typical capacity by running tests at <
25°C, 0.13A, 2.50V, unprotected cell >.
Why 0.13A? Because 0.2 * 650mA = 130mA = 0.13A. As in Panasonic's PDF datasheet we take C as the
minimum capacity, not the typical capacity.
Wtf am i? i am kreisl. When
i publish battery tests, i always include the standard test from the PDF datasheet so that the reader can directly compare my measurements with official specs (here: min/typ 650/700mAh for the Keeppower) of the product. Problem with the Eagletac CR123A cell is: there is no PDF datasheet available, so at least the cutoff voltage is unclear. Did they use 1.50V or 0.80V as cutoff or anything else??
Nuff now. It's Saturday night and time for
dsds show bye.:drunk:
