SamTexas said:
Huh? So you have been selling this battery for some time, yet you have never done any official test. So how did you come up with capacity and discharge rate?
Every single pack we supply has been tested and it delivers what I suggest it should. I haven't felt the need to post up data so far, we are kind of busy. When things quieten down in October, November, a report including tests on the different cells and also motors we offer is on my list of things to do.
The official battery voltage for the 22P Cell is 3.62V (at 1C discharge), the typical capacity is stated as 2150mAh at 0.2C, 2.75V discharge, minimum 2050mAh under the same conditions. Where does it state anywhere this is a 3.7V cell? My own tests indicate that at typical ebike discharge rates, 2.05Ah plus is to be expected, I have not been disappointed, that is what the measured pack capacity test we do on every single completed pack deliver. I do not hear complaints from my customers that these 22P packs do not deliver, nor do I hear complaints about packs made from these same cells, built by others. I have come up with some figures, 3.6V nominal and approx 2.05Ah per cell. I know these cells have a sloping discharge curve, just like every other cell of this type, that is why I use 14S instead of 13S. They are not meant to be a power cell, they have higher capacity than power type cells, they are cheaper than power type cells. It may surprise you, but we have been very busy this year and in 2 weeks our Annual Audit is due. When I have the new cells I am expecting and I have a little time, i will do some comparison tests on my capacity testing equipment, which can work at up to 6A.
SamTexas said:
Before you question the legitimacy of that independent test, you need to take a second look at the ACTUAL data presented. Where did it say 60% capacity at 3A? It clearly said 2048mAh at 3A discharge. That's 93%.
I'd love to see your test data and how you can justify even 2C continuous discharge, much less 4.5C.
Take a closer look at the 5A (2.27C) graph. The mean working voltage at that rate is only around 3.4V. This is supposed to be a 3.7V cell. And at 5A it only delivers 1927mAh (88%).
This ICR18650-22p cell is at best a 1C continuous cell, regardless of how you or Justin or anyone else claims.
I personally have not tested this cell, but I don't have any reason to doubt this independent test. But if your test shows otherwise, I will personally buy a few cells and verify the results myself.
Looking forward to see your test data.
Ok some figures from here on the 22P:
http://www.dampfakkus.de/akkutest.php?id=73
2A discharge to 3V = 2057mAh (100%) 7.311Wh (95.7% of the nominal rated capacity at 0.2C discharge, 2.75V cutoff)
3A to 3V = 2048mAh (99.6% of 2A Capacity) 7.16Wh
5A to 3V = 1927mAh (93.6% of 2A capacity) 6.475Wh
Firstly these figures are not to the stated cutoff point of 2.75V. If you refer to the data sheet posted up earlier by Neptronix, you will see on Page 5 the relative capacities at various discharge rates. It can be inferred from the stated capacity at 3C, that you should expect 95% of 2050mAh, 1947.5mAh. So actually, if you consider that the LVC is higher in the above test than the official 2.75V cutoff, the test actually correlates quite well.
The figures on the 22P cell are no more more overstated than any other cell type. Manufacturers will always try to put their products in the best light. I also think, that you do not really understand what the ratings mean in general. The max discharge rate does not mean that you should use it at that figure, it just means the cells can deliver that figure. Any cell operating at it's max C rate is at the limit. I believe Samsung come to that figure by determining the max current discharged whilst keeping the cell under a critical temperature. The 22P cell are not claimed to be a power cell, they are somewhere in the middle, with good power and reasonable energy density. There are more expensive cells available with better performance, but they are more expensive. If you want to attack the 22P cells, then attack just about every other cell out there, because they are all rated along similar lines. If you have such an issue with how batteries are tested/rated complain about that, not singling out companies and manufacturers.
My comment about 60% capacity refers to the graphs that are shown in the above site. Can someone please explain to me what exactly the graphs (not the figures) are supposed to be showing, because they make no sense to me. Why can't the graphs just show what the numbers indicate, that would make a bit more sense.
As you pointed out the figures give a working voltage of approx 3.4V at 5A, so for a 14S pack operating at a continuous discharge rate over what I recommend, the mid point is 14*3.4V = 47.6V. I would never recommend anyone uses the packs at that continuous discharge rate all of the time. If you refer to my site, you will see the Samsung are now listed as 3C, my recommendations for their usage is unchanged. You can see the SDI data sheet earlier that states 4.6C, I was calling them 4.5C until I changed it.
I also posted up Justin's data earlier on a finished pack which will not be as good as a single cell, due to losses in cabling, terminations and BMS. If you want to question Justin's data, please start a thread calling out his products and his credential, honesty etc. His Ezee packs use the same 22P cell that we use.
Here is the data for the Panasonic NCR18650PD (2900mAh claimed capacity, 10A Rated, so 3C plus rated, 2.5V cutoff), a very well thought of cell, an expensive cell, that I don't hear complaints about:
http://www.dampfakkus.de/akkutest.php?id=99
From the data:
2A (0.69C) discharge = 2695mAh (100%)
3A (1.03C) = 2703mAh (100.2% of 2A rate) (93.2% of the stated nominal capacity, 2.5V cutoff)
5A (1.72C)= 2544mAh (94% of 2A rate)
Personally, I don't understand what the big problem is. There are pros and cons to every battery. Your statements are singling out individual companies and products, when your dissatisfaction with batteries and their ratings apply to the whole industry. You don't qualify you nasty comments towards myself or others providing the products that are putting people on ebikes, by saying, just like everybody else, these batteries don't deliver the Max discharge rate whilst also maintaining a voltage that I am happy to see. FYI, I have changed the listing for the 22P cell, it now states 3C, my recommended usage is unchanged, I recommend a controller with max current approx 2C or a little over with the 22P cells. Anybody that has aspirations of big power, I suggest they use a different cell type. When I have the 20R and 29E cells SDI cells (both more expensive than the 22P), I will give my honest recommendation for those as well and give provide realistic pack capacity values after running my own tests.
Good Day
Paul
