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100kwh-hunter

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Mar 2, 2019
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I ordered a lot of cells, so far one seller delivered. (16 cells out of 96 cells from ali)
Those 16 are all within 20 to 22 M ohm, all are 3.290V ish, with mu yr1035 4 point meter.
I think they are good?(280 Ah 1C)
I will check for weight tomorrow? it seems to be important?

It was stated those where EVE cells, wrappings are good, no visible damage to the connectors, could be even new?

Anyway before i go charging them, "lock" them up to prevent "bulging"? or is this just a myth?
It is pretty easy for me to put a cast/lock around them to disable any movement. But is it necessary?
Just wooden sheets cut up, Or even a c clamp......nothing fancy.

Tahnks in advance for your answers, with best regards Igor
 

Korishan

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Just taking a strap and wrapping around the bank of cells would be fine.

Generally speaking, the expansion happens from charge/discharge cycles more than anything. So just sitting idle for a few months probably won't cause anything. Plus I think the increase in chance of expansion happens at high SoC (maybe >98%?).

But I've seen various different methods of strapping. And it doesn't have to be "tight", just really snug
 

Redpacket

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If you charge over approx 3.45 or 3.5 V it may cause bulging IMHO.
At 3.45V you still get to full 100% charge, no lost capacity. Just hold there for current to tail off = 100%.
3.65V is going "up the J curve" & not good for LiFePo4 & likely cause of bulging.
Any clamp system should allow for normal cell expansion/contraction & maintain a constant pressure eg have a spring on threaded rod.
 

fannel

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Jan 4, 2019
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Short question, Hunter:
"Those 16 are all within 20 to 22 M ohm, all are 3.290V ish, with mu yr1035 4 point meter"

On EVE website IR is listed as 0.20 to 0.30 m ohm. I bought me some 16 modules from aliexpress recently and IR was between 1.4 and 2.6 m ohm (using YR1030) and I'm worried that IR is too high and the modules may be too old. Yours are really 20 t0 22 mili ohms?
 

100kwh-hunter

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Mar 2, 2019
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yes mine are really around 20-22.
most 12 of them are 21 ohm
I think it is time to call the @Wolf on this one, but does he know about lifepo4 prismatic? that is the second question, but he know all about the IR
Probably i was lucky?
Second batch i will order next month.....you know that bullshit putlir is doing, i need to hurry up.
I dont care if a ali seller does not deliver..i will get my money back, the same goes as not as advertised....
From the 96 i orders i got some refund and one delivers those 16 with a IR of around 21....for two i am still waiting......
 

Dr. Dickie

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Sep 23, 2020
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341
yes mine are really around 20-22.
most 12 of them are 21 ohm
I think it is time to call the @Wolf on this one, but does he know about lifepo4 prismatic? that is the second question, but he know all about the IR
Probably i was lucky?
Second batch i will order next month.....you know that bullshit putlir is doing, i need to hurry up.
I dont care if a ali seller does not deliver..i will get my money back, the same goes as not as advertised....
From the 96 i orders i got some refund and one delivers those 16 with a IR of around 21....for two i am still waiting......
21 Ohms, or 0.21 mOhms? I got EVE cells, and mine were all below 0.20 mOhms. I actually could not get a reliable reading with 1060s (I think the problem was it wanted to show down the microOhms level), I had to use the YR-1030.
 

fannel

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"yes mine are really around 20-22.
most 12 of them are 21 ohm"

Hunter, I was worried that mine are probably too old because they have average IR of 1.4 milli ohms. They were advertised as 105 Ah but measured an average of 93 Ah (discharged at 30A using EBC-A40L). Now you are saying yours are averaging 21 milli Ohms and you are happy with them. In that case I shouldn't worry about mine being too high. One more question: the ali you ordered from, was it express or baba? Mine are from express, and I didn't have any high expectations, that's why I only ordered 105 Ah and not 280 Ah cells. I'm not sure what brand they are, so I'm not even sure if it is ok to use the EVE values as a reference. The cells have clearly been rewrapped, and wrinkles can be seen on the shrink wrap. Right now I don't know how to determine the original brand. I haven't unwrapped any yet.
 

fannel

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21 Ohms, or 0.21 mOhms? I got EVE cells, and mine were all below 0.20 mOhms. I actually could not get a reliable reading with 1060s (I think the problem was it wanted to show down the microOhms level), I had to use the YR-1030.
0.21 milli Ohms is in line with the specs on EVE website. Looks like you definitely got some good Grade A cells.
 

Redpacket

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You might want to check the meter is reading properly. Eg if you put both probes onto the one terminal, do you get very close to zero ohms?
I hope you are measuring directly on the actual battery posts, not on eg connecting link strips, etc?
 

100kwh-hunter

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🤒 hmmm yes 0.21 milli ohms.....:eek::eek: .....and 21 ohm, sorry ,my mistake.
There are NO damages on the poles and on the warping.

Atm they are now setlling to see if there is a self discharger, this weekend i will start to discharge them.
Charging was done per cell 5A on 3.45v.
I had to do, i think up to 3.6v for faster charging?
Up to 3.45v toke way to long and the chargers went down to 1.5 a.....so i just cut them off.
 

Dr. Dickie

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Sep 23, 2020
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To capacity test, you go from 3.65 V and discharge to 2.5 V. That will stress the cells a bit, but only need to do it once. 3.45 V top and 3.1 V bottom is just before the top end cliff and bottom knee of the curve so won't stress the cells and give longer life. LiFePO4 voltage curve is flat as heck. Impossible to get a reliable SOC from voltage. Also, can't really top balance before 3.5 or so, as one cell might be 70% SOC at 3.45V and another might be 90% SOC, only by getting up into the cliff area can you be sure.
Now all of this is my understanding, and I am just getting into LiFePO4, Andy of the Off Grid Garage in Australia has done a ton of testing and I think is just getting ready to do some more tests to determine optimum set-up for LiFePO4 cells:
Off Grid Garage
 

fannel

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Jan 4, 2019
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You might want to check the meter is reading properly. Eg if you put both probes onto the one terminal, do you get very close to zero ohms?
I hope you are measuring directly on the actual battery posts, not on eg connecting link strips, etc?
I think something may be wrong with the way the terminals were laser-welded. When I place both probes of the meter on the same terminal, I get a reading above 1 milli Ohm, but I think the meter is fine because when I place the probes on a copper bus bar from a Toyota Prius Hybrid battery, the reading is zero ohm. I may be doing something wrong
 

fannel

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Aluminum has higher resistance than copper .001Ω is close to zero Ω
Later floyd
Lol. Thanks for pointing out. The word mili can be misleading. Honestly, when it read 1.26 mOhm, I didn't realize this simply means 0.00126 Ohm. I guess I was trying to use the IR reading to gauge if my cells were too old or not. Looks like I'm beginning to hijack this thread
 
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