Are we all getting GRADE B cells??

[flemmingdjensen]

I have a facebook group in Danish where we build LFP batteries for our boats and since I opened the group I have recommended Basen Tech as being a reliabel supplier of GRADE A cells...

Now my frinds have bought 16 x 304AH CATL and they do not seem to be GRADE A. QR code seems to be scratched away and a few cells has minor dents in the casing.

I looked at this video yesterday saying that if we do not get certificates and Excel spreadsheets with test results for each cell then we are dealing with GRADE B...

Is this correct? Are we all getting rejected cells that cannot be used for fx Automotive purposes?

 

[houseofancients]

with basen sometimes you get lucky, sometimes you don't, which is why here most people dont order cells from them

 

[flemmingdjensen]

with basen sometimes you get lucky, sometimes you don't, which is why here most people dont order cells from them

At some point in time I considered Basen Tech to be a reliable supplier - but maybe not these days!

With supplier would be a better one?

 

[houseofancients]

At some point in time I considered Basen Tech to be a reliable supplier - but maybe not these days!

With supplier would be a better one?

lyuan - amy wan -
docan tech - jenny wu (jennywu896@gmail.com)
Qishou - https://m.alibaba.com/product/1600441382274/Shenzen-Qishou-Prismatic-Phosphate-Battery-Grade.html

 

[Rossman]

With supplier would be a better one?

The supplier with the least complaints here that I've seen is Shenzhen Luyuan

 

[LithiumSolar]

A big part of the problem is the industry does not define the terms "Grade A" and "Grade B". Either the cell meets the tolerances outlined in the standard testing/specifications or it doesn't. If that's what they're using to determine A vs B (and I'm not sure they are), then the B-category needs expanded (C, D, E, turd) in my opinion as there's a big difference between a cell that may be 0.01% off spec and one that's balloon-bloated.

 

[RCinFLA]

There are some new cells out there being sold. Alibaba is potluck on what you get.

304 AH cells have not been in existence that long (about same date as welded terminal studs appeared), so there is some use case out there really stressful on cell to get 304 AH cells already into the used cell aftermarket.

Don't have any definitive proof but most likely candidate is China EV market, likely metro EV buses. Los Angles bought some Chinese EV metro buses, and you can find a lot of horror stories about them online.

These thick electrode (>120 um) prismatic LFP batteries are not well suited for high discharge current rate applications like EV. The thick electrode causes lithium-ion migration out the electrode to get choked up when large flow rate due to high cell current demand happens. This is called electrode starvation and for these thick electrode cells starts to happen when cell current rate is greater than about 0.5 C(A). It causes increase in terminal voltage slump at high current and increased internal self-heating of cell. Prismatic cells do not dissipate internal heating well.

Best way to check if you got a used cell is doing a load test of between 0.2 and 0.4 C(A) load current. The amount of voltage slump from OCV rested voltage after about 90 seconds of load will tell condition of cell. The more used the cell, the more voltage slump for given demand current. Over useable life of cell this voltage slump can increase 3x to 5x from its original new cell amount.

It is also a good way to match cells. Matched cells will have same voltage slump after about 90 seconds with moderate load current.

Doing low discharge current capacity test does not represent the condition of cell well. High impedance cells will show respectable capacity at low discharge current rate. It is not until moderate load current is demanded that cell condition shows up.

 

[Rossman]

There are some new cells out there being sold. Alibaba is potluck on what you get.

I feel like there's a chance we are buying new, unused cells (from some of the vendors reviewed here) - but new cells which have been rejected by EVE for their automotive customers who demand a higher standard.

Like just because they are new, doesn't mean they are "Grade A" cells...it's really a minefield of risk, lol.

 

[Don B. Cilly]

The Standard Amy Wan (Shenzhen Luyuan) Spiel on cell grades goes like:

About the 280AH, we have two grades to choose from (both are the new version LF280K, brand new):
Grade A: fully matched, with the test data from the original factory. Its price has risen a lot, the newest price is $190/pcs.
Grade A- : Its internal resistance and voltage are matched, the capacity is not. We tested the real capacity of some cells,at 275-284AH. $111/pcs.

When EVE tests grade A cells, if some ones do not meet the specification (for example, the capacity is insufficient or there are some tiny defects in appearance), they will pick them out. These cells are A- I mentioned.
Many other sellers claim that it's grade A, but in fact, it's not.

I suggest grade A and full matched more, but its price is already very high, if you plan to use them in a solar system, grade A- is also an option.

I ordered A- (minus), I really don't care if I lose a small percentage of capacity.
I mean, almost half price, for the difference, I can assemble another battery, I'm almost certain to gain in capacity, am I not?
It's not as if I'm making it for someone else, and I never discharge past 50% with the much smaller ones I have anyway.
-

 

[John Frum]

The following is my guess on how battery production in China works.
The battery manufacturers don't have 6 sigma level quality control because they can't get super tight consistency from their supply chains.
So they just make more batteries in order to meet or exceed the required yield for the premium distribution channel.

Top quality batteries are thoroughly tested.
They do the quick/cheap tests first so they can skip the slow/expensive tests for cells that fail the quick/cheap tests.
The last 2 tests are likely the capacity test and the self discharge test.

Most of the cells that we get won't be fully tested because they failed a test somewhere along the way.
I would guess we also get fully tested and compliant cells that are production overage.
For the premium channel customers its not just about meeting or exceeding the spec but also about consistency.

 

[RV10flyer]

I have a 132kWh battery bank.

Three out of four of Amy's - Schenzen Luyuan "Grade A" 280aH 16S batteries do not have runners when I charge above 55.7V.

One out of four of Hayley's - Dongguan Lightning do not have runners above 55.7V.

Sanben's 320aH (really 304aH) and Trophy 220 aH both have runners above 55.7V.

FOUR out of ten batteries, I can take all the way to 57.6V or 3.6V per cell without having extra cell balancers installed. Just 10 individual BMS's with 0.15-2.0A balance current.

That is some poor manufacturing and QC. Sad. I stay just under 55.7V when charging and don't lose that much capacity. It's not a huge problem, just buy one more battery than you have planned. Along with 25% more pv? and you'll be fine.

 

[houseofancients]

The supplier with the least complaints here that I've seen is Shenzhen Luyuan

this is true, but 125 vs 169 luyuan both unshipped is quite the difference

 

[Rossman]

this is true, but 125 vs 169 luyuan both unshipped is quite the difference

I mean, in general, you get what you pay for, right?

Luyuan is providing a value-added service with their "expensive" ("grade A") cells that other vendors do not (matching per batch), and can provide EVE test reports, which others do not.

Obviously it's up to every individual whether the price premium and nearly universal favourable reviews are worth the additional cost for their use case.

 

[Don B. Cilly]

One wonders though... say you make XAh cells. Statistically, σ% of your cells turn out to have σ% less capacity. You could make them X+σ (+Y% for safety) and sell them for X. The result would be... all your cells meet or exceed capacity expectations.

Marketing-wise, it would well pay for the added expense, wouldn't it?
But then, manufacturers do (or tend to) not think that way. Marketing people do.
Maybe if manufacturers listened a bit more to marketing people, instead of always having to be the other way around... :·)
-

 

[Rossman]

One wonders though... say you make XAh cells. Statistically, σ% of your cells turn out to have σ% less capacity. You could make them X+σ (+Y% for safety) and sell them for X. The result would be... all your cells meet or exceed capacity expectations.

Marketing-wise, it would well pay for the added expense, wouldn't it?
But then, manufacturers do (or tend to) not think that way. Marketing people do.
Maybe if manufacturers listened a bit more to marketing people, instead of always having to be the other way around... :·)
-

Isn't this essentially what Intel does with CPU cores? They get a silicon disc with a bunch of cpu's printed on it, some of those will be great and get binned as a high clock speed part, others may have internal defects, so they will disable portions of that chip and sell it as a cheaper part.

 

[LithiumSolar]

Isn't this essentially what Intel does with CPU cores? They get a silicon disc with a bunch of cpu's printed on it, some of those will be great and get binned as a high clock speed part, others may have internal defects, so they will disable portions of that chip and sell it as a cheaper part.

The difference though is those are all sold with specific clock speeds. In the case of these cells, they're all LF280. We don't see them being engraved with LF275 or LF285.

 

[Don B. Cilly]

Well, no. They do just as EVE or other cells manufacturers do. Produce to specs, downgrade the not-to-specs.
I was suggesting producing over specs.

Now, in the case of CPUs, I guess that would be incredibly complicated to do. In the case of LFP cells... probably not :·)
-

 

[Rossman]

The difference though is those are all sold with specific clock speeds. In the case of these cells, they're all LF280. We don't see them being engraved with LF275 or LF285.

Yeah right now this is true, I was talking about this guys hypothetical scenario

 

[joanna_lannie]

Hey, do you know? In fact, all the prismatic LiFePO4 batteries, most of the so-called Grade A batteries are used to supply automobile companies. In fact, most of the batteries that we can get are between Grade A and B, that is, batteries that do not meet the requirements of automobile companies. Moreover, the battery grades are divided by each different battery factory, and there is no uniform standard at all. So, to put it nasty, the so-called Grade A batteries in our hands are actually the second-rank batteries in the battery factory.

 

[RobertGreen]

The entire Grade A, Grade B etc nomenclature is imprecise and not very useful IMO.
We just kind of wind up with a situation where any cell that doesn't fail basic tests or display visual imperfections gets marketed and traded as "Grade A."

I just want to buy cells which are newly manufactured, unused, and which meet the manufacturers specifications in every way, while lacking any type of defect.