EVE280 high C rates anyone?

[Bob142]

I'm not sure if this forum inspired unrealistic expectations or if the cells have changed recently.
From all the reading I did around here, I expected to get 280Ah too.

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.

 

[Sverige]

Well if a supplier has 1,000 or so B grade cells to shift and a potentially big buyer comes knocking, but is clearly going to carefully test the first few shipments, then it makes sense to send out some A grade cells first before swapping to B grade once the orders are coming thick and fast.

 

[cinergi]

I just want to thank everyone for the recent influx of testing and investigative work. I hope it's clear that I'm not particularly upset about these cells; as others have said, they provide a good value. All I want to accomplish here is to establish what's reality for these cells for everyone reading and researching these cells so they are better informed.

 

[Pyrofx]

Here is my take on it.
I ordered 280 amp hours. I don't care if they were used new gold plated or made of dung. I ordered 280 amp hours as advertised. If they do not meet that spec they are wrong. End of story.
Change the description to the capacity of the exact product it's not rocket science.

 

[Gazoo]

But even EVE has failed to give support to buyers that have purchased these in the grey market. I knew that going in so I never expected these grey market cells to perform up to that standard. I did expect the size and the screw thread size to meet the spec. I have not been disappointed.

I also don't feel I am leaving anything on the table. I paid $120 per kWh for a pack that had 80 percent usable capacity. That means per usable capacity I paid $150 per kWh.

Hello Ampster, I agree with you and I feel I got a great value as well. But there are several of us posting in this thread that bought from Michael in the group buy thread. Michael was told by Basen the cells were all capacity tested. I am not sure anyone expected the cells to be capacity matched even though Michael was told by Basen they would be.

When I received my cells I was really happy there was not any damage. That was the first thing I looked for. Then I noticed deformities with two of my cells. Aussiesim best describes it here and he received his cells from Xuba:

(1) EVE LF280 arrived damaged. | DIY Solar Power Forum (diysolarforum.com)

After I top balanced I tested the pack. 272ah's was a bitter sweet moment for me. I was hoping to get 280ah's based on what Michael was told by Basen, but knew I would be satisfied with better than 270ah's. Some people have cells that test at only 265ah's or less so I feel fortunate. But I feel bad for them. This was no fault of Michaels. Basen is totally to blame. Basen lied.

I think the point some of us are making is to not expect the full capacity from these cells. Suppliers are advertising them as Grade A 280ah cells. They clearly are not and while we know they are grey market cells, I am not so sure beginners would understand that unless they research the threads, and hopefully they will as EVE cells might be available again soon. It will be interesting to see capacity tests with the newer batches.

I am hoping the Lishen's will fair better. They are advertised as 272ah cells. The suppliers that have tested them, if you can believe them, claim they test better than 280ah's. And one forum member tested a cell and it exceeded 285ah's. Of course more testing needs to be done before we really know what the deal is with those cells.

 

[Gazoo]

What is more likely to happen is we will get similar results to Cinergi when we start using higher C rates

Probably but I will never be able to test at the high C rates he has.

 

[Gazoo]

One thing I've been thinking about lately--and I'm not 100% sure i've got it right but I'm going to throw it out there and see what the consensus is--is that one issue with mismatched (capacity) cells is that the cell that is already the lowest capacity is going to be cycled marginally harder than the rest, meaning more wear, meaning slightly accelerated degradation/capacity loss, sortof a slow gradual vicious cycle.

Of course if the difference in capacity is small, or the use case is very gentle/low intensity, or the pack is seldomly cycled all the way to near zero, its maybe not a big enough deal to even care about. And that describes the situation for most of us.

But I am curious, in theory does my thinking hold up?

It's logical that could be the case if doing full cycles on the pack. But if staying in the sweet spot between the knees I think the weakest cell would age the same as the rest. I could be wrong.

 

[cinergi]

Probably but I will never be able to test at the high C rates he has.

(not directed at you). My C rates appear to have no impact now that I'm further along in my testing. Cells that I've not used in a battery and/or put under high C rates are testing the same. Here's my results so far (11 cells):

268
269
270 x 3
271
273 x 2
278
280
281

 

[mmdb]

I have 20 280eve cells on the way ..And personally I don't care if cells are 262;267 or 280ah ..I still think they are great value compared to AGM s In my country

 

[Gazoo]

I have 20 280eve cells on the way ..And personally I don't care if cells are 262;267 or 280ah ..I still think they are great value compared to AGM s In my country

If that's acceptable to you then fine. It's not acceptable to me for a supplier to make false claims. And we need to start calling them out. It's bad enough to order directly from a supplier and receive lower than advertised capacity. It's even worse when we are told our cells have been capacity tested and they come up short.

 

[cinergi]

Now that I've tested 11 and have a statistically relevant sample, I'm exploring my options with Michael (and Basen through Michael). We'll see what Basen says, where we draw the line with respect to calling it a "bad" cell, etc ...

and to that end, I decided to buy 4 Lishen cells and put them through my same tests ... both so you can see apples-to-apples comparison with them and to see whether they would be a compatible drop-in replacement for EVE cells (assuming similar capacity, what does the IR look like).

Michael and I will determine what "right" is and make it so.

 

[Gazoo]

Now that I've tested 11 and have a statistically relevant sample, I'm exploring my options with Michael (and Basen through Michael). We'll see what Basen says, where we draw the line with respect to calling it a "bad" cell, etc ...

and to that end, I decided to buy 4 Lishen cells and put them through my same tests ... both so you can see apples-to-apples comparison with them and to see whether they would be a compatible drop-in replacement for EVE cells (assuming similar capacity, what does the IR look like).

Michael and I will determine what "right" is and make it so.

That sounds great. You are one of the few people capable of testing at high C rates and taking the time to share your results is appreciated.

I will be very interested to know what Basen has to say as well. I am sure Michael will take care of it one way or the other. Make it so....

 

[Gazoo]

(not directed at you). My C rates appear to have no impact now that I'm further along in my testing. Cells that I've not used in a battery and/or put under high C rates are testing the same. Here's my results so far (11 cells):

268
269
270 x 3
271
273 x 2
278
280
281

That is good to know. My two Valence RT batteries test a little higher capacity at higher C rates. But my testing with those has been at low C rates and they use cylindrical cells.

 

[Honuz]

I think you are most likely right.

But the issue is that the resellers (most of them at least) represent them as meeting manufacturer specifications (and some of them outright represent them as grade A, or claim to capacity test all cells individually). A few folks on the forum have really latched on to the (in my opinion unsupported and unlikely) claim that these are grade A cells, I think this is misleading to new members and newbies and leads to unrealistic expectations about cell quality and about the level of opacity and integrity of the market.

Almost weekly there are questions in the beginner section along the lines of "I bought matched grade A EVE cells from a trusted seller, do I still need a BMS or can I just use a charge controller" or "I bought well matched grade A EVE cells, do I still need to balance?"

If a cell does not meet its capacity specification (or any other specification), it is not a grade A cell, that doesn't necessarily make it a bad cell or a bad value (it could still be a great value), but it should be accurately and honestly represented by the seller (and if a seller misrepresents a cell, we should acknowledge that, not amplify the misrepresentation).

The funny thing about the grey market for raw cells is we know there are tons of B grade cells that get offloaded to the grey market to be sold at a discount, and most grey market cells are selling at deeply discounted prices, yet somehow nobody is selling or buying B grade cells..

Yea...but where are all those grade B cells going...! I bought Grade A myself...so...they are not here...?.
I plan to use between 10 and 90% dod max, and this 90% will most likely never be reached, cause I will adapt my way of life to protect the cells. I'm building my house at present and living in a tent, it's 5°C outside (well...inside too...?) and I got 2x20000 mah power bank to charge my phone and 2x 24watts PV.....lol. And some people in the world even got less then that.
You are perfectly right, let's be happy with our Grade B... I know I will.

 

[ArthurEld]

I am anxious to see what solution you guys come up with. I didn't buy my cells from Michael but I assume my cells are very similar to yours.

 

[Dzl]

Yea...but where are all those grade B cells going...! I bought Grade A myself...so...they are not here...?.

I'm building my house at present and living in a tent, it's 5°C outside (well...inside too...?) and I got 2x20000 mah power bank to charge my phone and 2x 24watts PV.....lol. And some people in the world even got less then that.

I lived for 6 months in similar conditions except you have me beat on the frigid temperature (I was towards the other extreme 25*C to 40*C in a tent but just feet from the sea) and I had you beat on the count of austere power (21W PV panel and 14,000mAh power bank). Longterm living in a tent in 5*C sounds rough!

 

[Hedges]

How do I get 10% more capacity in a 2p16s 48v configuration buy using a few more cells?

You could buy 2 more cells for 7% more capacity and wire them 2p17s for 51V (assuming your BMS could deal with it.)
Lead-acid is so much easier ...

 

[cinergi]

You could buy 2 more cells for 7% more capacity and wire them 2p17s for 51V (assuming your BMS could deal with it.)
Lead-acid is so much easier ...

hehe yeah I've been wondering if I could do a 17s configuration (BMS won't do it though); the working voltages go over 60, however.

 

[Marinepower]

I am watching this space with interest as I have 4 EVE 280 cells ordered the end of October en route from Basen.

My expectations are now tempered.

Personally, I am less concerned about not reaching full capacity than having cells with high self discharge or significantly mismatched cells. I fully understand those expecting full capacity. I was also represented that these cells were 'Grade A'.

Self discharge is (apparently) caused by less than perfect / ragged factory cutting of the foils that make up the cells, which can cause small internal voltage leakage / shorts btw anode and cathode. Or at least, this is what one resource has claimed. Potential safety concern.

Any observations on these cells self discharge? I recognize that proper testing of self discharge takes a least month to complete....

MP

 

[snoobler]

Given that the as-received cells have been sitting for 30+ days while in transit, consistent voltages in the high 3.2X range is a good sign that self-discharge isn't a concern.

 

[Marinepower]

Given that the as-received cells have been sitting for 30+ days while in transit, consistent voltages in the high 3.2X range is a good sign that self-discharge isn't a concern.

Thxs for your reply. I was thinking something similar but the cells are shipped at 50% discharged so the voltages will all be very close and their start voltage / capacity unknown.

 

[JoeHam]

Self discharge described here:

 

[Sverige]

Self discharge described here:

That’s a fantastic video from someone who seems to know what he’s talking about.

I noticed this in the comments. Didn’t someone post to this thread, or one of the other 280Ah threads recently that one of the cells they’d received had a damaged QR code?

 

[cinergi]

That’s a fantastic video from someone who seems to know what he’s talking about.

I noticed this in the comments. Didn’t someone post to this thread, or one of the other 280Ah threads recently that one of the cells they’d received had a damaged QR code?

This one (mine)?

 

[Sverige]

This one (mine)?

Yes, I probably saw that in your other thread. Does that cell show any signs of reduced performance compared to the others?