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  1. D

    Paralleling packs with a protection diode?

    Battery fire is a nice vivid consequence of idiotic effort of Louis Rossman. rg12, what difference do you expect between the two batteries ? There is a safe voltage difference range for connecting the batteries. Just don´t understand why you are still active on such trials...
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    Li-ion cells cycle ageing

    Calendar aging test update. Seven cells passed 200 days milestone.
  3. D

    Li-ion cells cycle ageing

    Selfdischarge update. Another two cells from cycle aging test checked (Samsung 29E7, Sanyo GA), both seems to be OK. Then new cells Samsung 30Q No4 and Samsung 40T No3 checked, both have only a few full charge/discharge cycles. It is obvious that even new 30Q No4 (orange chart curve) has...
  4. D

    Li-ion cells cycle ageing

    Here is selfdischarge comparison of 30Q and VTC6. I made some selfdischarge voltage drop measurements on the cells in calendar aging. Obviously at 100% SOC new 30Q has markedly higher selfdischarge than others.
  5. D

    Li-ion cells cycle ageing

    30Q selfdischarge has been mentioned several times in this threat as well as in others. After cycle testing, it was obvious that remaining aprox 90 % capacity of 30Q cell could be used in some not demanding application. So flashlight was my choice. Charging the cell to 3,8 - 3,9 V only...
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    Li-ion cells cycle ageing

    New update, Samsung 29E7 and LG M50T added.
  7. D

    Battery Voltage

    Assuming the voltage is reading from Daly app. I am not sure if you have chance to recognize possible balancing from voltage reading on the cells, probably not. Even if your charger has really 58,8 V at the output, 58,1 V reading on battery at the end of charging is normal because there are...
  8. D

    C rating for low power 18650s

    Not sure how did you achieve to find this test. :) It is protected cell with protection circuit installed. Moreover the test is from the time, when lygte had non true 4 wire measurement. Those are reasons for the different discharge characteristics, mainly at 5A.
  9. D

    C rating for low power 18650s

    In fact 2,5 V cut-off happened between 37 and 38 min. However temperature logging time was set to 1 minute, the graph didn´t catch the temperature peak. Temperature was already going down at 38 min. For 0,625A peak temp corresponds to 2,5 V cut-off.
  10. D

    C rating for low power 18650s

    I was curious what is Panasonic 18650B real discharge characteristic. Panasonic official data list : My results - I used 5A because of specification 4,9 A max continuous discharging current :
  11. D

    C rating for low power 18650s

    Hillhater, Panasonic 18650A is old cell, old technology. Maybe it is only cell with such pronounced divergence. Moreover, 18650A graph doesn´t look like real measurement. Capacity at 2C isn´t so much higher in newer specification from 2012. We can see similar tendency at some cells. Compare...
  12. D

    Spot Welding Copper Strips to 18650 Battery Cells

    You need reliable bullet-proof solution, I can reccomend Higo connectors. https://www.higoconnector.com
  13. D

    C rating for low power 18650s

    I can confirm the probable temperature effect on the capacity, see real measurement on Panasonic 18650B. However, the energy at 3A discharge is lower thanks to the higher voltage drop.
  14. D

    Li-ion cells cycle ageing

    What I found out from 30Q and VTC6 cycling data is that the quick capacity loss at the beginning happened mainly during the first 8 cycles. DOD for both are slightly over 70%. However these are high power cells. For high capacity cells like M36 or 35E I see different picture, where initial...
  15. D

    Li-ion cells cycle ageing

    You probably want to clean aging data with help of data collected from cycling ?
  16. D

    Li-ion cells cycle ageing

    Percentage values used only to help differ the lines at 100% SOC. Yes, I know that temperature variations and ZKETECH are two obstacles to accurate measurement. I declare 25 ± 1°C but trying to have better range, something like 25,3 ± 0,5°C. Of course, your 0,1°C range is ideal. Because...
  17. D

    Li-ion cells cycle ageing

    You know, 100 days is too short time for relevant results IMO. Trend of degradation will be different at 300 – 400 or even more days. Moreover, my calendar aging study is again little bit problematic because of unsufficient amount of samples (only one for each case). However, I can show the...
  18. D

    Li-ion cells cycle ageing

    Inspired by your testing I also started calendar aging during summer this year. Twelve pairs of the cells are relaxing at room temperature, always one at 100% and one at 50 % SOC : LG M36, M29, HG2, MJ1, M50T Samsung 35E, 29E6, 30Q, 50E, 29E7 Sanyo GA SONY VTC6 Each 100 days are cells checked...
  19. D

    Li-ion cells cycle ageing

    Manufacturer´s Ali-shop (RD tech, or also Hangzhou Ruideng Technology Co., Ltd) : https://rdtech.aliexpress.com/store/923042 Go to Products/DC Digital/DC Voltmeter 5 Digit
  20. D

    Li-ion cells cycle ageing

    Second round of testing : in the range 0 – 4,3 V is accuracy ± 0,1 mV, range 4,3 – 10 V again stable offset -1 mV. In my opinion 6,- USD for voltmeter which has accuracy 0,004 % at 2,5 V (0,0024 % at 4,2 V) is very reasonable.
  21. D

    Li-ion cells cycle ageing

    I checked precise 4 wire voltmeter (see page 13) on PDVS2mini precision digital voltage source. To my surprise accuracy and linearity of this cheap chinese voltmeter is unbelievable. In the range 0,5 - 4,3 V absolutely accurate without any deviation. Bellow 0,5 V stable offset -0,1 mV. In...
  22. D

    40T Cells Voltage Drops While Not In Use

    It´s common that cells have little bit higher voltage drop after charging, depending on charging parameters. Lets sit the pack few days without BMS and measure voltage of all groups. BMS is still the first suspicious. However, your effort to kill the cells by high load inevitably will bring...
  23. D

    Li-ion cells cycle ageing

    No, it is not comparison of three different cells, it is measurement on the same cell (LG HG2 No2). Frankly, I am surprised by such enormous capacity decline, moreover, the cell was stored at proper SOC and temperature. Maybe it was cell from lower quality batch, who knows.
  24. D

    Li-ion cells cycle ageing

    Let me remind LG HG2 No2 : LG HG2 No2, production date November 2017. Purchased fom nkon in September 2018. Cell stored at aprox 25 – 40 % SOC, 15° - 20°C. In December 2018 capacity 2 909 mAh at 3 A discharge, measured at ZKETECH EBC-A10H. In September 2019 : 2836 mAh at 1A, 2804 mAh at 3 A...
  25. D

    Li-ion cells cycle ageing

    Well, just be aware that cycle aging is only part of the whole picture. It doesn´t include calendar aging. Interesting fact : capacity of SONY VTC6 after 700 cycles is the same as initial capacity of LG HG2 before cycling. LG HG2 initial capacity 2792 mAh 4,2 – 2,5 V / 1 A SONY capacity...
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