EVE280 high C rates anyone?

[Dzl]

Statements that I've missed out on the nuances of what nominal means in this context are beside the point entirely and another discussion altogether.

Please review the above screenshot, in this case this has nothing to do with the term nominal. Minimum capacity is defined in the datasheet

I fully share your feelings that resellers should be held to a higher standard than they currently are, and when they misrepresent things it should not be accepted or excused. At the same time, if you are unwilling to review a datasheet, and do some limited amount of due diligence and research, I feel that buying from the grey market and building your own battery may not be the best path for you. Its a fraught market, and there is a lot of minor and sometimes major misrepresentation and lack of transparency. It definitely requires doing research and reading datasheets and doing your own due diligence. And even at the end of that process, there is still uncertainty, risk, and you only have maybe half the info you need to make an informed purchase. Its a very different experience than even buying from some other large marketplace like Amazon.

The information on the datasheet comes from the manufacturer, it can be trusted to a much higher degree than anything the reseller claims. Though a datasheet represents what a product should be not necessarily what it is, and that is especially true of grey market cells.

Another thing to be aware of is a raw cell is not a retail product, and these resellers are not exactly 'consumer facing' businesses. Cells are a component, you will find that when you buy high or low quality components, from eastern or western sellers, its a normal part of the buying/selling process to review the datasheet. This is normal, not an exception to the rule. Datasheets are very very valuable in making informed purchases and design decisions. Not something to be avoided.

it's about arriving at an agreed upon definition that meets the requirements of what is specifically being discussed: minimum rated capacity.

280AH

Reaching agreement with fellow humans on just about anything can be frustrating as hell! Humor helps!

 

[ArthurEld]

Looks like most of cinergi's cells are out of spec.
I suspect at least a few of mine are too.
What I don't know is if that is typical.
And I don't know if the low capacity or other issues will effect reliability or # of cycles.

I assume the cells I got are the same as everybody has been getting. But I have no way of being sure.

I guess part of the reason the cells are so cheap is because we are taking a risk when we buy them.

 

[Dzl]

Looks like most of cinergi's cells are out of spec.
I suspect at least a few of mine are too.
What I don't know is if that is typical
I assume the cells I got are the same as everybody has been getting. But I have no way of being sure.

I think this is a good and unanswered question, it wasn't until pretty recently that very many people started rigorously testing the cells and documenting their findings in detail.

So it could be that recent examples are outliers, or it could be that this was fairly common all along but the issues didn't become clear until more people began to approach verification of capacity more rigorously.

I guess part of the reason the cells are so cheap is because we are taking a risk when we buy them.

Definitely. This is what everyone buying and cells on the grey market need to understand I think. Not all cells or sellers are equal, but as a general rule, buying grey market cells exposes you to more risk and more uncertainty, and the possibly of greater variance between cells or between batches of cells. And I think those factors are very much baked into the great prices.

 

[Sverige]

Is anyone charging or discharging their 280Ah EVE cells at or above 0.5C and observing 280Ah? I'm having a bear of a problem getting more than 250-260 out of some of them and I'm wondering if it's because I've been pushing 120 amps in and 220 amps out on occasion. Out of 36 cells, I've tested 22 and at least 6 of them are pulling my battery bank down well under 280Ah. I've individually tested 2 of those 6 with a tester at 10 amps and only got 250-260Ah out of them. One of them even intermittently stopped discharging at least twice during the test due to very high internal resistance.
TIA!

As far as I can see the OP’s question remains unanswered, and it’s an interesting one. Out of all the folks who’ve bought these 280Ah cells, there must be a few who are pushing them hard in terms of current during charge and discharge, and who might be in a position to comment whether they’re seeing the full 280Ah?

 

[cinergi]

As far as I can see the OP’s question remains unanswered, and it’s an interesting one. Out of all the folks who’ve bought these 280Ah cells, there must be a few who are pushing them hard in terms of current during charge and discharge, and who might be in a position to comment whether they’re seeing the full 280Ah?

As the OP I don’t need an answer. I am getting 270 and less on cells I had never stressed so my high C rate concerns are unwarranted.

 

[ArthurEld]

As the OP I don’t need an answer. I am getting 270 and less on cells I had never stressed so my high C rate concerns are unwarranted.

That is too bad. You also got a messed up QR code.
My testing hasn't been progressing lately. I need to get back to it.

 

[Bob142]

I am working on that right now. I have 4 EVE 280s sitting unused on a shelf that I received from Craig 6 months ago that he tested out to 280Ahs per cell. Not quite a time machine, and statistically insignificant, but it's the best direct comparison I can make.

To recap for those unfamiliar, I've been balancing and testing my recently acquired Basen cells in 4S packs:

• Top balancing to cell voltage of 3.65V.
• Constructing packs managed by an Overkill Solar 4S 120A BMS
• Charge current of 30A, discharge current of ~60A.
• Using a TF03K battery monitor for pack capacity measurements.
• The room has been at a consistent 68F (20C) during all charging and discharging.
• I haven't done any cell-level capacity tests as I don't think those are useful data points for me in practice.
• The three Basen packs have yielded 265Ah, 274Ah, and 274Ah in the first round of tests. (More details: balancing setup, 1st pack, 2nd pack, 3rd pack.)
• In the case of the 274Ah pack tests, my inverter shut down when it hit 11V. Only the 265Ah result was due to BMS cell level low voltage protection (2.5V).

I'm top balancing the Craig cells now and will perform the same pack-level capacity test using the same procedures and equipment.

I'm back from my trip in the TARDIS.

First balance and discharge with the Craig cells yielded 276Ah at the 4S pack level before the inverter shut down at 11V (capacity meter and BMS screenshots below). It's the best pack result I've had after one cycle through the four packs. However, given the single test per pack and the imprecision of my equipment I see the differences as noise.

On my bench, the score after the first round is:

• Basen 1: 265Ah (94.6% of rated capacity of each cell) [This one had a runner. Looking forward to another test.]
• Basen 2: 274Ah (97.9% rated capacity)
• Basen 3: 274Ah
• Craig 1: 276Ah (98.6% rated capacity)

Looking at % of rated capacity I was able to get out of 4S packs it's all good to me. Basen 2 & 3 along with Craig 1 had more to give beyond what my inverter would take. The same is true for 3 out of 4 cells in Basen 1. So the vast majority of the cells themselves have slightly more capacity than what's stated in these results. Did they have 4-6 more Ahs? Maybe not, but since my use case is AC, if the inverter can't use it, it's not there. So far I have no issues or concerns with the recent cells.

 

[Dzl]

Reaching agreement with fellow humans on just about anything can be frustrating as hell! Humor helps!

I agree. Effective communication is hard sometimes, especially when we get frustrated or feel our point is not being understood or being misrepresented. I know I could be communicating better and more constructively here--probably we both could--but I apologize for my part in that.

One thing I can say is that speaking broadly you and I share the same goals (1) clear, agreed upon, well understood info, and (2) holding resellers to a higher standard (or at the least not just accepting their BS), (3) accurate data.

And another place we can agree is that the current level of reseller marketing integrity and transparency is subpar to say the least and is not acceptable.

Stepping away from the specific points that we don't see eye to eye on, I think mostly we share the same broad goals and should not lose sight of that.

Now back to your regularly scheduled programming..

 

[Dzl]

Bob 3 questions:

WTF is a TARDIS...?
Do you plan to swap out the low cell and retest that pack?
Is the ~900W shown in the screenshot representative of the average discharge rate more or less?

 

[Bob142]

WTF is a TARDIS...?

Short version: it's at least a time machine.
Long version: https://thedoctorwhosite.co.uk/tardis/

Do you plan to swap out the low cell and retest that pack?

No, I plan on retesting Basen 1 intact. I'd like to see how it does a second time. Making sure I didn't botch anything in the top balance or connections etc. With three other packs so consistent after the first round I'd like another data point at the pack level to see if maybe I'm the reason it didn't perform as the others did.

Is the ~900W shown in the screenshot representative of the average discharge rate more or less?

No. The BMS is recording the max when I first turn on the little space heater before it levels out after a couple seconds. It sits at just about 765W for 5 hours, so it's been about a 60A load +/- a little depending on the pack voltage during the discharge test. Here's another BMS screenshot from the tail end of the test as an example. The BMS and TF03K battery monitor have been in agreement on the current measurements.

 

[Dzl]

No, I plan on retesting Basen 1 intact. I'd like to see how it does a second time. Making sure I didn't botch anything in the top balance or connections etc. With three other packs so consistent after the first round I'd like another data point at the pack level to see if maybe I'm the reason it didn't perform as the others did.

Good plan, if you have the means and the time, you could also do a single cell test on the low cell, see how it does on its own. Though this is of limited practical value since it won't be used on its own.

I do agree your other 3 tests are pretty consistent (and anecdotally seem to be right in the center of mass of the capacity tests for these cells that people on the forum have been reporting)

 

[Honuz]

@Sillyputty Sorry if it seemed I was poking fun at you or anyone else in the thread. I've just found the communication issues a little entertaining as a casual observer.

I think it is a wise policy to never buy batteries from a vendor until they provide a datasheet for what they are selling. Everything else is just words. The datasheet should also state the test conditions that result in the battery meeting specifications. If the vendor says they are selling batteries that meet the spec, it is proper to hold them to it. If the seller tries to avoid being specific about the minimum capacity of the battery they are selling, then it is buyer beware.

Yeah... But now you got to put the price in the mix, some default are acceptable in regards of the price.

 

[Bob142]

I do agree your other 3 tests are pretty consistent (and anecdotally seem to be right in the center of mass of the capacity tests for these cells that people on the forum have been reporting)

It depends on whether you're referring to individual test results or battery pack results. I believe there are small single digit Ahs being left on the table in my pack-level tests. I can't quantify them yet as I have no good DC loads to try and draw the final bit of juice out of the packs. Based on voltage alone I suspect there's 2+ Ahs left. But until I can measure it, it's just conjecture.

 

[Dzl]

It depends on whether you're referring to individual test results or battery pack results. I believe there are small single digit Ahs being left on the table in my pack-level tests. I can't quantify them yet as I have no good DC loads to try and draw the final bit of juice out of the packs. Based on voltage alone I suspect there's 2+ Ahs left. But until I can measure it, it's just conjecture.

Apologies if it was stated previously but what voltage is your inverter cutting off at?

 

[Bob142]

Apologies if it was stated previously but what voltage is your inverter cutting off at?

11V. Follow the breadcrumbs in this post and this one. You can see the cell voltages in the screenshots for the three packs that the inverter cut out on and the approximate cell voltages after a short rest when the BMS tripped for a low cell voltage in the first test.

 

[Bob142]

No, I plan on retesting Basen 1 intact. I'd like to see how it does a second time. Making sure I didn't botch anything in the top balance or connections etc. With three other packs so consistent after the first round I'd like another data point at the pack level to see if maybe I'm the reason it didn't perform as the others did.

Basen 1 retest complete. Virtually identical results. Cell #2 was a runner and I got a little over 265Ah from the pack. I even redid the top balance to make sure I didn't dream that I completed it correctly the first time. Screen shots of the BMS a moment before it cut off discharge due to low voltage on cell #2, and the remaining pack capacity according to the battery monitor.

So I've only got one runner out of 16 cells across two different purchases. Seems like I beat the odds.

 

[Sillyputty]

I got a little over 165Ah from the pack

265, I hope?

 

[Bob142]

265, I hope?

Yes! Edited, thanks.