Then I try to charge and discharge my cells, at first it work fine as state in their example curve, but at the end of discharge, it drop down faster than it should and record a >2260mAH for a cell discharge at 2A take approximately 80 minutes from 4.2V to 3.0V, Samsung suggest discharge to 2.75V. This mean if combining 2 pieces it still have at least 4500mAH suppose to work better than his original battery. Note that Samsung don't sell 2300mAH battery, if I discharge it to 2.75V there suppose have 23++mAH, so they label it 2400mAH, will be 4800mAH on most notebook battery pack.
There is however it isn't, I have come out with 2 assumption:
1. Sony rated 4400mAH work better than 4400mAH.
2. Samsung built in PTC (Positive Temperature Coefficient) thermistor have higher resistance than Sony, thus result in battery pack have higher voltage drop across PTC, this assumption was made base on I trust my supplier cells since they always do so. And the cells have thicker isolator among electrode, result in higher cells resistance than Sony but it is safer to practicing this.
Higher voltage drop across PTC result in faster false triggering of Near End (~7%) or end of discharge (0%) voltage reach (So battery board fell that cells is empty even there may be still around 10-20%) .
At different current flow, higher current will have more voltage drop across PTC, resulting in EDV shift to lower to allow correct power meter, EDV various base on the preset value defined by the specified setting in a particular pack.
Newest battery IC with built in impedance tracker will track the impedance of cells for different battery, reduce the need for technical people to set the value for fine tune according to different type of chemical. Example is bq20Z70/Z80/Z90 family, but it is still expansive so rarely a factory want it, only big company adapt it to reduce the complexity and time for implementation/production of a battery for a system.
So this few weeks I shall study how the manufacturer set EDV for Samsung Cells compare to Sony cells. I will do some experiments to prove this since hard to get all the spec for those industry cells.
Sorry for my incompatible for this issue since this is first time I use Samsung cells, along the years I seen minimum case of leakage ever occur on Samsung cells and Sony cells, but Sony have some no so good history record so I decided to go for Samsung which seen safer. No to look down on Sony cells, it is powerful and they perhaps have making their lesson over the years.
Learn a lesson here, sorry my customer. I believe this will not occur on notebook battery that originally using Samsung cells, which I will contact another customer who originally cell is Samsung to verify this.
P/S：Sony EDV0 is 3050mV, will track back Samsung from my old file. EDV1 and EDV2 is checking now hope will get conclusion soon. There are more than two version of bq2084, most commonly use is v133 and v143 which have different dataflash format. I am really sorry as I am not the best technical. I suggest those who want to do refill battery, learn properly, some battery is easy to refill but some make people headache.
Update(27June): Base on EDV Discharge Rate and Temperature Compensation Programming in manufacturer's manual, I found that EDV is calculate base on
EDV0,1,2 = n (EMF * FBL – |ILOAD| * R0 * FTZ)
Update(2July): Finally I get back the battery and I check what happening, strange enough, I didn't found any problem occur on the battery, it register a capacity of 4667mAH after a few cycle use, although it didn't reach 4800mAH, but at least it won't let you down. As I know, all brands of cells is sell in this way, they sell the cells base on closer capacity, example 2330 will be rate as 2400mAH but not 2200mAH. 2200mAH usually it will only have 2100+mAH nominal capacity. Even I discharge the battery, it will still do more that 4700mAH in 3Ampere discharge current. Now I am start to think, Sony label some very high capacity cells example 5200+mAH cells and sale it at spec 4400mAH to the manufacturer, to show that their battery is strong or because the market demand it but in their stock is all high capacity, so they remark it to lower capacity.
In fact, mAH is just a reference, many people don't know that high power cells that can continuously supply more current (a few time more) than normal cells, if discharged in low current, can supply more WHr even it discharged at same amount of mAH, that is why some people prefer using unit WHr than mAH. But high power cells is more dangerous in my point of view, some high power cells can supply more than 10A continuously, if short circuit occur inside the cells (dielectric is too thin, more tend to be punctured by crystal built up inside the cells), can result in explosion.
This is similar to processor manufacturer produce many low frequency processor because market demand on it is higher, it doesn't mean that the processor is slow. So it can be over clock to higher speed. Example some 1.6GHz can over clock to 2.0GHz without rising it voltage. When they speak about global huge market, they want cash flow rather that store the stock since electronic products going to become obsolete very fast.
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