EVE 304 Cells from 18650batterystore & zke-40 testing.

[RCinFLA]

I need some education.

Does the factory load-test the battery and then put a stamp or code on there telling what the battery pulled during that qc test?

No, they don't have to, unless a large customer requires it, which the customer will pay extra for. There are other processes they have to do, like charge forming, and impedance measurements that predicts the capacity without investing all the time to do a full capacity test run.

Time is money. Pre-lithiating anode graphite to aid solid electrolyte growth is a big time saver and manufacturing cost reduction. It also yields a bit greater cell capacity by not consuming as much cathode lithium during charge forming process.

 

[Alkaline]

0.2 to 0.4 C(A) is a good range with reasonable load test on cell.

I wish I could convince folks with zke-40A tester to program in some 5 minute rest periods sequences during the discharge cycle. Observing the cell voltage slump from rested no-load voltage to loaded voltage after about 3 minutes into load gives info on cell impedance.

You can try, but their wallets will cry

On a side note RcinFLA I used to think you were a know-it-all stealth troll, but you called it fair and square. I will now head your advice with sincerity going forward.

 

[Bud Martin]

So I hope we will hear what 18650 has to say to OP. Replacement cell offered?

 

[Sam Cho TX]

I am concerned my testing equipment may be the problem, but going by numbers the 303 did in fact pass capacity on the ZKE so I'm not entirely sure what to think.

I really thought either the cell testing to 297 (label 302) or 292 (label 292) were going to be the issue, but they did fine. I mean this is very strange how a cell can pass capacity on .1c but then do really bad when on a .2c load.

So I will have someone else test my cells see what they think I reached out to them and he is well known and see what he has to say (and no its not sun fun kits they refused to test, already asked and was rejected). I just want to make sure my victron, or zke and bms is ok.

 

[sunshine_eggo]

I am concerned my testing equipment may be the problem, but going by numbers the 303 did in fact pass capacity on the ZKE so I'm not entirely sure what to think.

I really thought either the cell testing to 297 (label 302) or 292 (label 292) were going to be the issue, but they did fine. I mean this is very strange how a cell can pass capacity on .1c but then do really bad when on a .2c load.

So I will have someone else test my cells see what they think I reached out to them and he is well known and see what he has to say (and no its not sun fun kits they refused to test, already asked and was rejected). I just want to make sure my victron, or zke and bms is ok.

Another option is to confirm current values with a clamp DC ammeter. Correlation of a 30A current on the ZKE with a 30A current on the shunt with a separate meter gives you confidence that they should report comparable values.

 

[No.15]

0.2 to 0.4 C(A) is a good range with reasonable load test on cell.

I wish I could convince folks with zke-40A tester to program in some 5 minute rest periods sequences during the discharge cycle. Observing the cell voltage slump from rested no-load voltage to loaded voltage after about 3 minutes into load gives info on cell impedance.

So I have a question. I'm going to pull out my big dc load I have pretty soon (its in storage because I recently moved). It's full programmable scpi and I can write scripts for it. Could you let me know what you consider a good test set? What load, I assume .5c, but I am wondering when I should program in the rests. After a certain load amount or after a certain time amount? Etc.

 

[rcr1978]

Make sure your testing temperature is similar. I did mine in my shop during the winter and had some temp swings between battery tests and could tell the difference after testing some batteries twice. Example: My shop is heated and never goes below 48F, I would go out to work and crank the heat to 70F and when done for the day turn the heater down when not out working. The early tests the batteries were starting at 50 and the later ones were 65+ and performed better. I should have done all mine in the house were there were no temp swings.

 

[RCinFLA]

So I have a question. I'm going to pull out my big dc load I have pretty soon (its in storage because I recently moved). It's full programmable scpi and I can write scripts for it. Could you let me know what you consider a good test set? What load, I assume .5c, but I am wondering when I should program in the rests. After a certain load amount or after a certain time amount? Etc.

For these thick electrode cells, electrode starvation begins to occur above about 0.5 C(A) cell current. This increases the cell overpotential voltage necessary for given demand current.

0.2 to 0.4 C(A) is a good test current range. High enough to show excessive overpotential and low enough to avoid thick electrode lithium-ion starvation.

Stopping discharge periodically and allowing cell to recover to rested unloaded open circuit voltage allows to measure overpotential at various points on discharge current. It normally takes about 5 minutes to fully reach unloaded open circuit voltage equilibrium. After the rest period when load is picked up again, the voltage slump from OCV after about 3 minutes of load is the overpotential.

Normally, overpotential is fairly constant for given cell current from 90% to 20% state of charge. Keep cells in 20-30 degs C range during tests as overpotential voltage increases below +15 degs C.

The more I look at cell 303 discharge graph, I think it was a screw up where the copper/graphite negative electrode thickness was too thin. The anode capacity is too small in comparison to cathode LFP capacity. Possibly mixed up 280AH cell anode print copper foil with 304AH cathode print aluminum foil thickness. I think 304 AH cathodes may have a small amount of graphene powder mixed in, so cathode print is not really thicker for the higher 304AH capacity. Graphene is expensive so it is used sparingly to improve LFP cathode efficiency.

 

[Alkaline]

For these thick electrode cells, electrode starvation begins to occur above about 0.5 C(A) cell current. This increases the cell overpotential voltage necessary for given demand current.

0.2 to 0.4 C(A) is a good test current range. High enough to show excessive overpotential and low enough to avoid thick electrode lithium-ion starvation.

Stopping discharge periodically and allowing cell to recover to rested unloaded open circuit voltage allows to measure overpotential at various points on discharge current. It normally takes about 5 minutes to fully reach unloaded open circuit voltage equilibrium. After the rest period when load is picked up again, the voltage slump from OCV after about 3 minutes of load is the overpotential.

Normally, overpotential is fairly constant for given cell current from 90% to 20% state of charge. Keep cells in 20-30 degs C range during tests as overpotential voltage increases below +15 degs C.

The more I look at cell 303 discharge graph, I think it was a screw up where the copper/graphite negative electrode thickness was too thin. The anode capacity is too small in comparison to cathode LFP capacity. Possibly mixed up 280AH cell anode print copper foil with 304AH cathode print aluminum foil thickness. I think 304 AH cathodes may have a small amount of graphene powder mixed in, so cathode print is not really thicker for the higher 304AH capacity. Graphene is expensive so it is used sparingly to improve LFP cathode efficiency.

Hey I have some test results for 280K, what do you think? https://diysolarforum.com/threads/what-is-going-on-here-just-got-zke-40.49076/

 

[Capt Bill]

Well after seeing a slew of videos it seems to me that there is not much difference between grade A and B, so why not try some from 18650batterystore. Anyway I previously tested some of the EV grade from Sunfunktis and was pretty happy with the results, but they have raised the price a bit since then, here is that thread: https://diysolarforum.com/threads/new-toys-arrived-zke-40-tester-sun-fun-kits-eve-lf304-cells.56015/

I could use a few batts so when the 304 came back in stock I ordered 4.

Well... they are packaged Ok I would say, not as nice as Sun Fun Kits but no damage, however, I can already see some issues. I see 2 of my cells are 302AH and 303AH so this is already below the 304 18650store claims on there page... guaranteeing to pull 304 AH.

Also the welds on the terminals look pretty bad looks like they even burned the terminal plastic a bit.

Anyway my total cost was $149.33/cell shipped so lets see how they test. The Sun Fun Kits cells where $202/cell shipped so we are about $53.33 more per cell.

Nice to see the pictures and get your details. Thanks

 

[Nonlin]

Well after seeing a slew of videos it seems to me that there is not much difference between grade A and B, so why not try some from 18650batterystore. Anyway I previously tested some of the EV grade from Sunfunktis and was pretty happy with the results, but they have raised the price a bit since then, here is that thread: https://diysolarforum.com/threads/new-toys-arrived-zke-40-tester-sun-fun-kits-eve-lf304-cells.56015/

I could use a few batts so when the 304 came back in stock I ordered 4.

Well... they are packaged Ok I would say, not as nice as Sun Fun Kits but no damage, however, I can already see some issues. I see 2 of my cells are 302AH and 303AH so this is already below the 304 18650store claims on there page... guaranteeing to pull 304 AH.

Also the welds on the terminals look pretty bad looks like they even burned the terminal plastic a bit.

Anyway my total cost was $149.33/cell shipped so lets see how they test. The Sun Fun Kits cells where $202/cell shipped so we are about $53.33 more per cell.

Were the labled as Grade A on the site? Just ordered some 304ah labeled as new Grade A from 18650 store but worried they are cons too.

 

[Sam Cho TX]

No they were grade B, but 18650batterstore said they are supposed to pull full capacity. They did not honor this, I ended up not even using these 4 cells and in the long run I probably saved a headache and now just get grade A cells.

 

[hardtop]

I bought 4 cells and a BMS from 18650batterstore. The BMS was DOA and I passed the 7 day return period. That was an expense for me and a JK 200A is what it was. It was an open box. Selling defective open box products is bad practice, they could have tested it before shipping it or gave me a new one like everyone expects.

Then the black matt top material on the cells are coming up. They are grade A and I'm unsure of the exact capacity but I can get 3kWh @ 120V AC at the Victron 12/1200 inverter from full to empty. I'm happy with that.

I didn't need to wait the 3 months from China to receive them so there is that, but the whole point from buying from an American company was to avoid feeling like I got ripped and I lost on that. It may have been better for me to order from China and wait because the Winston rep was incredibly communicative and professional. Those are good batteries, I'd go with that brand. The EVE's seem incredibly fragile. Just having threaded rod close can be a risk. That isn't the case with the Winstons, those cells are tough. They are a little more but they are automotive grade and they take a charge at colder temperatures than normal.

 

[Sam Cho TX]

You only have 7 days to return a DOA product?

 

[hardtop]

Yep! Daylight robbery.

 

[Sam Cho TX]

Well they have good prices but they are cutting corners everywhere, I guess if you wanted the cheapest possible go with them but expect same level of service as an aliexpress seller.

From what I understand they are no longer sending test reports even with grade A cells.

BTW you have some; looks to be like little craters in your cells did you see that?

 

[740GLE]

Not to mention he has exposed conductor that’s unfused and close to making contact at the inverter.

I’d tighten that up ASAP.