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Beware of Docan Technologies (Issue Resolved)

Unfortunately with all stuff from china. Not just batteries. You get what you get. Although their products are a million times better that what they use to be. If it wasn’t we wouldn’t even be having this conversation.
Don’t like it ? Buy American or European and pay 10 times more. Sad to say. We are at their mercy if we want good and cheap.

When you buy these cells, they are testing failures. It actually says a lot about the quality of the vast majority of cells that pass. If you buy them, buy extra. If you buy the real cells, just order what you need.

The vendors should just stop lying. That really is what it boils down to. It is not hard or expensive to test a cell and give real specs. Then you just group them by capacity and send the test results. $150 for a tester and a dollar for electricity.
 
I raised the issue with Docan and after some back and forth they are willing to send me a replacement cell, but I need to pay for the shipping. (~$46). I can keep the damaged cell. I suppose I'll need to dispose of it responsibly which means a trip to the recycle park but that's a weekly trip anyway.
 
I just started testing 35 from Docan, but it will take me over a month to complete!
Yes, it is time consuming. Each cell takes about 18 hours. In total I have purchased 16 "grade B" cells and 32 "grade A" cells. I have tested them all multiple times, using multiple testers. The factory rejects averaging 273ah, with the two lowest being 264ah, and 2 reaching the 280ah capacity. Every one of the grade A cells were 290ah or above. With my admittedly small sample size, I recommend buying extra cells to prevent the lowest cells from limiting the capacity of your battery bank. You still get more bang for your buck than the grade A cells.
 
Yes, it is time consuming. Each cell takes about 18 hours. In total I have purchased 16 "grade B" cells and 32 "grade A" cells. I have tested them all multiple times, using multiple testers. The factory rejects averaging 273ah, with the two lowest being 264ah, and 2 reaching the 280ah capacity. Every one of the grade A cells were 290ah or above. With my admittedly small sample size, I recommend buying extra cells to prevent the lowest cells from limiting the capacity of your battery bank. You still get more bang for your buck than the grade A cells.
Are you really ahead though if you have lower capacity, have to buy a tester, test each cell, buy extra cells, and possibly shorter battery lifetime?
 
Are you really ahead though if you have lower capacity, have to buy a tester, test each cell, buy extra cells, and possibly shorter battery lifetime?

I'd argue absolutely! Eliminating a runner especially in a 1S configuration will allow you to get the most of the pack. Docan advertises grade A, but I am already seeing a 10AH delta on cells, though I'm only 3 tests in so far. I will post the entire lot once complete.

I'm not sure I understand what you mean with potential shorter lifetime?
 
Are you really ahead though if you have lower capacity, have to buy a tester, test each cell, buy extra cells, and possibly shorter battery lifetime?
Depends on your use case. If you test those 264ah cells at 0.5C, you will find they are more like 250ah. Most people don't use solar storage at this rate (who wants a 2 hour battery). Generally speaking, 80 to 40 amp draw is what you should shoot for. If you cycle the cells every single day from 100% to zero, that capacity difference can really add up over 2000 cycles. Most people should not have a need to run this way, so the answer is much more difficult to figure out. I started this process to basically figure out if the claims of 98% efficiency were true, that is a very impressive figure. It boils down to 99% from my testing, provided you keep the cells in a temperature controlled environment. So I started with the intent of testing every cell, and thus others can benefit from my experience. I purchased multiple testers, and compared calibrated instruments to the more reasonably priced alternatives. It boils down to.... "the EBC-A40L is the best bang for the buck, but only tests at 40 amps". You can even buy much cheaper testers that will give you good results, but at less than half the draw rate. You really don't see a significant difference in cells until you get above 60 amps, but that is significantly more costly to achieve. So for solar storage, testing capacity at 40 amps seems to work well.
 
How many Docan purchasers felt they were getting Grade A cells? Shenzhen Luyuan pricing was always higher than Docan, Basen, and all the other sellers. Why did anyone think they would be getting Grade A premium cells? It wouldn't surprise me if Amy Wan saw sales fall off a cliff as the Grade B peddlers flooded the market. In the cutthroat Chinese marketplace, I imagine getting less than you paid for is far more likely than getting more than you paid. All speculation on my part. I have no lifepo4 cells nor any relationship with resellers.

Sunfunkits has a youtube video from some time ago. They demonstrate the difference between Grade A and non-Grade A cells. The Grade A cell voltage sag is much less than non-Grade A. As I recall, even a 30A load on lower grade cells would shows significant voltage sag.
Umm because they lie and can get away with it?

What are you going to do? Return it? They know its not possible...

In the end they know you will still buy because most are not going to pay the 40-50% higher price of grade A... But maybe they will pay more in the long term, time will tell.
 
I’m top balancing/testing cells 20-24 from Docan from two different orders, they never told me they were grade A or not just said new, voltage and IR matched. I am noticing a difference in staying balanced depending upon how I top balance them.

My first two 12v 280ah batteries I used the cheep 10 amp power and it took between 74-76 hours for the parallel top balance, these cells stay within .007 and don’t need balancing so far

Then on the next one I assembled it with BMS charged until almost full and then set up the parallel top balance to finish. This one stays about .010 difference and depending on charge/discharge amperage can go as high as .025 triggering balancing.

It seems like balancing them slower has better results, and having a little patience can get you better performing cells even from the same cells.

These are from the first batch, I am starting on the second batch now.
 

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Yes, it is time consuming. Each cell takes about 18 hours. In total I have purchased 16 "grade B" cells and 32 "grade A" cells. I have tested them all multiple times, using multiple testers. The factory rejects averaging 273ah, with the two lowest being 264ah, and 2 reaching the 280ah capacity. Every one of the grade A cells were 290ah or above. With my admittedly small sample size, I recommend buying extra cells to prevent the lowest cells from limiting the capacity of your battery bank. You still get more bang for your buck than the grade A cells.

I think there are other things like an X-ray test to show manufacturing faults, people put too much sway on the capacity.

Btw the tests should be a watt hour test not just capacity so it takes voltage into account because watts = volts * amps.

So if you have a cell that is weak its volts will be low, it may have the same capacity but if it basically was "meh" the whole time did you really get a good cell.

so maybe a cell that averages 2.98 volts during a test vs a cell that is 3.2 volts; if both provide 280AH then cell 2 clearly provided more watts as cell 1 would be 2.98 * 280 = 834 WH vs 3.2 * 280 = 896 WH

This is something many people are ignoring only looking at capacity and ignoring the voltage.
 
I think there are other things like an X-ray test to show manufacturing faults, people put too much sway on the capacity.

Btw the tests should be a watt hour test not just capacity so it takes voltage into account because watts = volts * amps.

So if you have a cell that is weak its volts will be low, it may have the same capacity but if it basically was "meh" the whole time did you really get a good cell.

so maybe a cell that averages 2.98 volts during a test vs a cell that is 3.2 volts; if both provide 280AH then cell 2 clearly provided more watts as cell 1 would be 2.98 * 280 = 834 WH vs 3.2 * 280 = 896 WH

This is something many people are ignoring only looking at capacity and ignoring the voltage.
I don't have an X-ray to test with.
I use amp hours because that is the unit that the spec sheet uses.
Having tested extensively, the voltage sag doesn't show up until 60 to 80 amps rate in the majority of cases. Not meeting the rated amp hours capacity always shows up even at 40 amps.

I am not ignoring, simply sharing my experience testing at rates up to 160 amps.
 
How many Docan purchasers felt they were getting Grade A cells? Shenzhen Luyuan pricing was always higher than Docan, Basen, and all the other sellers. Why did anyone think they would be getting Grade A premium cells? It wouldn't surprise me if Amy Wan saw sales fall off a cliff as the Grade B peddlers flooded the market. In the cutthroat Chinese marketplace, I imagine getting less than you paid for is far more likely than getting more than you paid. All speculation on my part. I have no lifepo4 cells nor any relationship with resellers.

Sunfunkits has a youtube video from some time ago. They demonstrate the difference between Grade A and non-Grade A cells. The Grade A cell voltage sag is much less than non-Grade A. As I recall, even a 30A load on lower grade cells would shows significant voltage sag.

I will just link this, it is interesting. Don't be surprised if it gets taken down since it is easy to be sued.

 
Another 16 cells delivered today...
 
Umm because they lie and can get away with it?

What are you going to do? Return it? They know its not possible...

In the end they know you will still buy because most are not going to pay the 40-50% higher price of grade A... But maybe they will pay more in the long term, time will tell.

Interesting, I was just curious and thus went to see price differences. Did I get the right site?



So, except for shipping and shipping time, virtually identical prices.
I would prefer the EVE terminals to be honest, since EVE rates them for the full 280 amps current. The LF280K version is supposed to be optimized for longevity.
 
I mistakenly had the wrong seller and my complain was NOT about Docan Power. With docan power everything is fine.

The complaint was about Shenzhen EEL Battery Co.,Ltd
 
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