Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
High and low drain cells mixed
#21
OK for a reference I discharged these 4 cells

Cell#1  7130 UR18650FM 42.0 4.1766 2573
Cell#2  7131 UR18650FM 41.6 4.1716 2555
Cell#3  7132 UR18650FM 41.5 4.1791 2562
Cell#4  7133 UR18650FM 41.6 4.1725 2529

Discharge 1 Amp for the Pack

Here is the chart Nice and smooth.

Wolf
jdeadman and completelycharged like this post
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply
#22
(08-21-2019, 09:22 PM)OffGridInTheCity Wrote: Very interesting topic.  I'm currently building an additional 'battery' of 14s120p.  I have mostly 1,500 Panasonic NCR18650As with average IR (according to my OPUSs) in 60mOhm range.  I have another 180 MOLI ICR-18650M(s) that have much higher IR (120mOhms) and dramatically different knee on discharge curve.
Both cells are in the 2900mah range.
OffGridInTheCity,

I happened to get some NCR18650As and some ICR18650-28As in my last batch. I don't have any MoliEnergy cells in the 2900mAh range unfortunately. So for a test I was thinking of putting 3 NCRs and 1 ICR into my tester and see what happens.
It would sort of simulate your potential environment as the IR on the Opus is within your range. Repeatable IR on the Opus of course is not an option.
Proper measured IR on the NCR is ~35mΩ and the ICR ~50mΩ. I will charge these cells on my SKYRC and then run them through a complete discharge/charge cycle on my analysis board.
Would 500mA per cell be about what you would want? So 2A for the pack of 4.

Wolf
jdeadman likes this post
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply
#23
(08-23-2019, 12:58 PM)Wolf Wrote: Would 500mA per cell be about what you would want? So 2A for the pack of 4.
 Yes sir.
Reply
#24
(08-23-2019, 02:33 PM)OffGridInTheCity Wrote:  Yes sir.

Then so it shall be. 3 NCR and 1 ICR should have the results by Saturday evening.
Wolf

Addendum:
What should I use for voltage ranges to simulate your charge and discharge environment?
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply
#25
Currently I'm doing 4.0 to 3.5 but as the battery ages/degrades and I need to increase DOD to get same kwh/day out of the battery, I plan to expand to range out to 4.15 to 3.3 before I start thinking of replacing the battery.
So let's say 4.1 to 3.4? as aged but not yet at the limit. (i.e. don't want you to have to run multiple tests etc - appreciate the effort here Smile )
Reply
#26
(08-23-2019, 03:33 PM)OffGridInTheCity Wrote: So let's say 4.1 to 3.4?  as aged but not yet at the limit.    (i.e. don't want you to have to run multiple tests etc - appreciate the effort here Smile )

No problem I think its educational and informative for the whole board to see what goes on in the unseen electron world.
Plus I am as curious as you are Big Grin

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply
#27
In terms of working voltage ragne, Wolf's test data, when looked at a little differently seems to show a good voltage range and it's below 4V....

If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
Reply
#28
(08-23-2019, 04:44 PM)completelycharged Wrote: In terms of working voltage ragne, Wolf's test data, when looked at a little differently seems to show a good voltage range and it's below 4V....


Interesting. A while back I started to track ah/v (discharge) on daily basis after the PV array stops providing input.  My though was that this metric would show (over years) a degradation as the battery ages it its ability to delivery ah per battery (48v) voltage drop.     

Initially, I tracked it down to 48.5v (3.46v/cell) and the average has been 79ah per battery volt drop.    (my battery is 780ah @ 48v).  In Aug (thanks to @Sean and other discussions like this) I raised the cut-off to 49.5v (3.53v/cell) to get ahead of discharge knee and I see the ah/v has increased to 101ah per battery volt drop.    

Until this graph/discussion - I was thinking of DOD as 'pretty linear' but this graph highlights that it may not be a linear as I was thinking.
Reply
#29
Without the brilliant data from Wolf this would not be possible to work out :-)


As different chemistries "age" the peak of the chart will move higher or lower in voltage, typically lower.

The chart is Wh discharge per 50mV drop in cell voltage (20 data points) - I missed this detail out the chart.

While raising th elower cut-off may well give more Ah per V it is not really giving you anything and may be a worse situation to be in.

The point is related to cell calendar life degredation and charge voltage, higher the charge voltage level (and temperature) over time the quicker the cells deteriorate. So, if you operate the pack constantly at a higher charge state this aging process comes into play, along with higher self discharge losses.

Raising the lower discharge cut-off in my view is actually detrimental compared to reducing the maximum charge voltage. If you mix high and low discharge cells in a pack (big IR differences) then probably stay in the middle of the voltage range.

In one perspective draw a horizontal line on the chart at your desired DoD (are above the line relative to the area below) and this will give you your most consistent operating voltage range (leas change in V for the energy discharged).


If we take cell 1 for example, which for the data points adds up to 4.15Wh discharged energy.

For 91% DoD (energy) the voltage range is actually 3.95V to 3.35V

If we only want 50% DoD the voltagre range is 3.7V to 3.5V (2.19Wh / 53%)

Also not that these area all voltages under load and not resting cell voltages..... so the lower voltage should be exact for cut-off purposes but the higher voltage depends on your cell recovery/IR. The 3 minute on-off discharge type test would help show the relative recovery voltages through the discharge process.

This is maybe the non-linear type of discharge chart you may be reffering to.
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
Reply
#30
(08-23-2019, 05:56 PM)completelycharged Wrote:  The 3 minute on-off discharge type test would help show the relative recovery voltages through the discharge process.

Give me a little time on that. 
I will write it into my sketch 3 min on 3 min off.  Obviously got to do it with a relay or Mosfet with a resistor bank and a cutoff voltage to leave the relay off at the end.

Anyone want to share some code that I can add to the loop they have already written to turn a relay on and off with certain time parameters and include a cutoff voltage?

If not this ameature scketch writer will bumble throug it. LOL

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply


Who read this thread?
72 User(s) read this thread:
EnergyOasis (09-10-2019, 12:29 AM), stok (09-12-2019, 12:30 PM), piglet (Yesterday, 11:44 AM), smileypete (09-03-2019, 10:07 AM), mackoffgrid (09-13-2019, 03:56 AM), Emiel (09-13-2019, 10:09 AM), foamovercast (08-30-2019, 01:49 PM), drbacke (09-11-2019, 08:49 PM), juanjo57 (09-13-2019, 02:19 PM), Doin it (Yesterday, 11:54 PM), 100kwh-hunter (09-03-2019, 01:28 PM), winny (09-13-2019, 08:51 AM), intra (09-10-2019, 12:26 AM), OffGridInTheCity (09-13-2019, 04:01 PM), kevinjaye (09-11-2019, 09:07 PM), ajw22 (09-03-2019, 10:10 PM), madmike (08-27-2019, 09:48 AM), metalorn (08-29-2019, 12:31 PM), 7h0r (09-01-2019, 05:15 AM), Whiteraven1386 (09-09-2019, 07:10 AM), Eduardo Kang (09-12-2019, 05:59 PM), donnib (09-05-2019, 01:18 PM), James-w (09-12-2019, 08:29 PM), hschlech (09-08-2019, 07:03 AM), chad (09-06-2019, 02:27 AM), diib (08-23-2019, 04:03 AM), MBard (08-27-2019, 06:30 AM), Cobra_Phil (09-02-2019, 03:07 AM), berthfield (08-22-2019, 03:17 AM), dragonfly (08-25-2019, 05:36 AM), LPG (09-06-2019, 01:40 AM), drnickriviera (Today, 12:27 PM), 3xtr3m3 (09-03-2019, 01:20 PM), Otakar (08-25-2019, 08:23 AM), Jonisingt35r (09-02-2019, 11:11 PM), stevelectric (08-29-2019, 12:00 PM), Generic (09-11-2019, 04:11 AM), Oz18650 (Yesterday, 09:10 PM), ChrisD5710 (09-12-2019, 04:41 PM), Grumplestiltskin (08-29-2019, 03:34 AM), Jon (08-26-2019, 06:41 PM), SWEwall (09-11-2019, 07:44 PM), Geek (09-13-2019, 12:15 AM), Hanssing (09-12-2019, 11:39 PM), jesusangel (09-11-2019, 06:13 PM), watts-on (09-06-2019, 03:50 PM), jdeadman (09-13-2019, 12:53 PM), Franky Beuselinck (09-09-2019, 01:59 PM), PAF (09-13-2019, 06:13 AM), A + A (09-11-2019, 09:40 AM), Korishan (09-12-2019, 12:21 PM), mike (09-03-2019, 10:32 PM), Sean (09-03-2019, 12:16 PM), djuro (09-04-2019, 05:50 AM), jm1 (09-09-2019, 12:50 AM), Freedom3737 (08-30-2019, 03:29 PM), Wolf (09-13-2019, 07:07 PM), OhmGrown (08-23-2019, 07:15 AM), clupton (09-01-2019, 03:36 PM), jaeger-audiodesign (09-11-2019, 02:17 PM), emuland-metroman (09-06-2019, 05:09 PM), chuckp (09-13-2019, 12:37 PM), Jim Jr. (08-31-2019, 02:33 PM), Riplash (09-11-2019, 03:01 AM), Bubba (09-13-2019, 10:49 PM), avm131 (08-23-2019, 05:52 PM), Zvonko000 (09-13-2019, 07:04 PM), Ibiza (09-13-2019, 05:34 PM), completelycharged (09-13-2019, 02:47 PM), Crimp Daddy (09-11-2019, 01:13 AM), Chablis_m (08-24-2019, 01:15 AM), daromer (09-11-2019, 06:24 PM)

Forum Jump:


Users browsing this thread: 1 Guest(s)