Search found 333 matches

by docware
Jan 15 2021 5:18pm
Forum: Battery Technology
Topic: Battery Voltage
Replies: 3
Views: 104

Re: 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 always v...
by docware
Jan 04 2021 4:47am
Forum: Battery Technology
Topic: C rating for low power 18650s
Replies: 43
Views: 794

Re: C rating for low power 18650s

I finally found the Lygt test for the ncr18650, 3100mAh cell.. A little different to the “Official” trace.. ( but at 0.5 and 5.0A discharges ) 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 ha...
by docware
Jan 04 2021 4:45am
Forum: Battery Technology
Topic: C rating for low power 18650s
Replies: 43
Views: 794

Re: C rating for low power 18650s

.. on the 5A discharge temperature trace,..... ..is the 38min peak at the 2.5v cut off ? ....or is that cell still discharging after the 38 min peak temp point..? Ditto for the 0.62A temp trace at 300 mins ? In fact 2,5 V cut-off happened between 37 and 38 min. However temperature logging time was ...
by docware
Jan 03 2021 6:16am
Forum: Battery Technology
Topic: C rating for low power 18650s
Replies: 43
Views: 794

Re: C rating for low power 18650s

I was curious what is Panasonic 18650B real discharge characteristic. Panasonic official data list : Discharge Rate Characteristic for NCR18650B.jpg My results - I used 5A because of specification 4,9 A max continuous discharging current : Panasonic 18650B No2 0,2C - 1A - 5A.jpg Panasonic 18650B No2...
by docware
Jan 01 2021 10:59am
Forum: Battery Technology
Topic: C rating for low power 18650s
Replies: 43
Views: 794

Re: 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. Panasonic 18650A spec 2012 version.jpg We can see similar t...
by docware
Dec 30 2020 9:30am
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 433
Views: 69720

Re: Spot Welding Copper Strips to 18650 Battery Cells

Now just need to attach some balance leads (no BMS in this pack). Any recommendations on compact connectors I can mount on the packs for the occasional balancing exercise (99% of the time these packs will just be bulk charged). Was thinking of either sub-d or pcb headers. You need reliable bullet-p...
by docware
Dec 30 2020 5:06am
Forum: Battery Technology
Topic: C rating for low power 18650s
Replies: 43
Views: 794

Re: 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.
Panasonic 18650B.jpg
Panasonic 18650B.jpg (225.28 KiB) Viewed 300 times
by docware
Dec 27 2020 3:29pm
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: 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%. Samsung 30Q initial capacity drop.jpg SONY VTC6 initial capacity drop.jpg However these are high power cells. For high capac...
by docware
Dec 27 2020 3:28am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

Pajda wrote:
Dec 25 2020 7:57am
.... also there is a huge influence of cycle life (inserted capacity and DCIR tests) for some cells which has yet to be removed from the data.
You probably want to clean aging data with help of data collected from cycling ?
by docware
Dec 25 2020 5:58am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

I think that most significant issue with this particular test is a ZKETECH EBC-X0510 accuracy (stability). Second issue is temperature stability. 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 measu...
by docware
Dec 24 2020 4:39am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

Excellent news, can we expect your "first impressions" soon? :D 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 a...
by docware
Dec 23 2020 1:21pm
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: 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 for ca...
by docware
Dec 23 2020 6:12am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: 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
by docware
Dec 21 2020 5:02pm
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

any purchase sources more reasonable than direct? 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. 4,3072 V.jpg 8 V.jpg
by docware
Dec 21 2020 7:47am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: 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 the range ...
by docware
Aug 23 2020 1:54pm
Forum: Battery Technology
Topic: 40T Cells Voltage Drops While Not In Use
Replies: 7
Views: 251

Re: 40T Cells Voltage Drops While Not In Use

So I charged row 9 to level with the rest and disconnected the bms to see if row 9 drops without the bms and it did. It dropped 0.03V within 48 hours while the rest were perfectly balanced and dropped only 0.002V in those 48 hours. It´s common that cells have little bit higher voltage drop after ch...
by docware
Jun 28 2020 5:46am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

This test show comparison between three particular cells, so the only one conlucison is valid for direct comparison of this three cells. 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, mor...
by docware
Jun 25 2020 3:09pm
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: 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, measure...
by docware
Jun 23 2020 1:48am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

If there's one thing I learned in the barrage of data I've seen over the past year or so here, it's what NOT to buy. That alone has saved me a lot of time and money. Well, just be aware that cycle aging is only part of the whole picture. It doesn´t include calendar aging. Interesting fact : capacit...
by docware
Jun 21 2020 10:21am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

I'm sure he's going to continue testing cells in the future anyway. Very probably not, cells testing became boring. Vegetable growing is much more interesting and enjoyable. :) 1.jpg 3.jpg Comparing cells tested at different times, by different people with different equipment is impossible. Wrong, ...
by docware
May 25 2020 3:15pm
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

Samsung 35E has 87,4 % of initial capacity in the cycling interval 4,1 - 3,4 V / 2,5 A discharge. In standard range 4,2 - 2,5 V at 1 A discharge has 93,6 % of initial capacity and 93,6 % of initial energy. Samsung 35E No2 after 700 cycles 4,2 - 2,5 V 1 A disch comparison.jpg Samsung 35E DCIR after 7...
by docware
May 24 2020 2:13pm
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

Currently preparing charts for all three cells.
by docware
May 24 2020 9:19am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

Sunday afternoon, no brain capacity for such work :)
But have something better, source Excel file :
DCIR rise Excel file.xlsx
(16.15 KiB) Downloaded 58 times
Edit - DCIR without zoom :
DCIR without zoom.jpg
DCIR without zoom.jpg (178.36 KiB) Viewed 221 times
by docware
May 24 2020 6:20am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

The final batch of data - Samsung 35E, 50E and LG HG2 finished 700 cycles. Samsung 35E 700 cycles.jpg Samsung 50E 700 cycles.jpg LG HG2 700 cycles.jpg Capacity decay comparison zoom offset 24.5.2020.jpg DCIR comparison 24.5.2020.jpg Just as a matter of interest, here is capacity decay comparison wit...
by docware
May 15 2020 8:42am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 507
Views: 56241

Re: Li-ion cells cycle ageing

If someone start building his own bike with tuneable controller, or when i think about E-mopeds like Surron, the peak C-rate usually is much higher there. Surron as example has 6kW peak power and around 1900Wh battery (Panasonic PF) so already above 3C or 9A per cell. Still not true continuous in m...