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Another Recommendation for Docan / Amy Zheng - EVE LF280K

Seriously everyone: keep it civil. I've made similar posts like OP in the past on equipment I bought. Don't assume someone posting something like this is an agent from a vendor. Making these kinds of posts allowed us to find good/bad vendors in the first place when people started buying these kinds of cells.
 
I must say, the posts have been much more humane and reasonable since the initial wave, mostly. For that I thank you all. Perhaps my responses were a notch too caffeine infused, as well, lol.

I don't agree with the idea that I or anyone new should refrain from posting here if they lack the specialized tools to test internal resistance and capacity, but I can understand that those parameters are quite important in any review of a vendor.

As far as the black covering, I'm kind of confounded as to what to do. These batteries will be going in a friend's system that I'm building for them, and while appearance isn't the focus, I don't want it to look like actual garbage either. The adhesive holding it on is indeed rather strong, and it will leave a thick, unsightly residue when it is peeled.

What will peeling it off prove? As I understand it, all this will tell me is whether this battery is "EV grade" or not "EV grade". Am I missing anything? Genuinely all I care about is 1) whether the initial capacity is within 5% of rated capacity, and 2) whether it will last 15-20 years with 75-80% of that capacity still usable, with light use and when properly cared for. My assumption was that most people on this thread are in a similar boat, but I've discovered that may be far from the case.
 
Just wanted to encourage anyone on the fence about ordering from Docan / Amy Zheng to go ahead and take the plunge. My experience was perfect. Amy (amy@docanpower.com) was very helpful and responsive. I was a little sketched out about the prospect of initiating a PayPal payment to "energy2021@yeah.net", but after seeing that address mentioned in another thread, I went for it.

I ordered four EVE LF280K cells from the Houston warehouse (total cost: $567.00), and received them in central Ohio only 3 days later. The cells were packaged extremely well and arrived without a scratch. The codes indicate all cells are genuine and were manufactured on the same day, a little over half a year ago. And what really topped it off is that all four cells measured the exact same voltage, to the THOUSANDTH: 3.298V.

Overall I'm very impressed, and just wanted to encourage anyone that was in my position about a week ago. The price was better than anywhere else I could find, and the product literally could not be of higher quality. I hope to order many more cells for friends and clients in the future.
thanks for the input!
 
I thought Docan sells “Top Grade” these days. Or did they change their marketing again?

For the OP, I’d say assemble your battery and use it. Unless you are trying to obtain 99% functionality out of the battery in a mission critical system, they will be fine.

One great test is to try and pull .5c for 30 min then check the cell voltages.

For me I’d much rather design a system that max pulls .1c and baby the cells.

I say this as a former Docan customer (4/22) if I’m in the market for cells again, I’d look at them.
 
The issue with Docan (and I warned them against doing it) is that they believe the 'B' that EVE engraves over the QR code these days is going to cost them business so they 'recreate' the QR code. There is another thread on this - here is a link to a picture in that thread. So they sand off the original QR code with the 'B' and replace it with the same QR code without the 'B'.
Thing is, if they would just have been honest about the 'B' cells and sell them as such, people wouldn't have had an issue. Doing this however...

And this is also why OP had that backlash - just wrong timing.
 
Thanks guys.

One great test is to try and pull .5c for 30 min then check the cell voltages.

I would need to figure out how to consistently pull a set amount like .5c, and how to even measure that in the first place. That is interesting though. How accurate are the results from a test like that? Do you just compare energy used to the percentage change?
 
I would need to figure out how to consistently pull a set amount like .5c, and how to even measure that in the first place. That is interesting though. How accurate are the results from a test like that? Do you just compare energy used to the percentage change?

You need a battery tester specifically to do this, like a ZKE. I wouldn't. Put it in a battery, charge it, balance it, and put a load on it and use the BMS read-out as an estimate.
 
You need a battery tester specifically to do this, like a ZKE. I wouldn't. Put it in a battery, charge it, balance it, and put a load on it and use the BMS read-out as an estimate.
That's a good point, I had forgotten my BMS would be capable of such things. How accurate do BMS readouts tend to be?

So they sand off the original QR code with the 'B' and replace it with the same QR code without the 'B'.
Thing is, if they would just have been honest about the 'B' cells and sell them as such, people wouldn't have had an issue. Doing this however...

And this is also why OP had that backlash - just wrong timing.

This explains a tremendous amount. Thank you
 
That's a good point, I had forgotten my BMS would be capable of such things. How accurate do BMS readouts tend to be?



This explains a tremendous amount. Thank you
A good tool would be a shunt more accurate than the bms and probably the best way overall to monitor the battery think of it as your gas gage I put them on all my systems
 
I would need to figure out how to consistently pull a set amount like .5c, and how to even measure that in the first place.

What I typically see people doing to do this kind of test is to hook the battery up to a load and measure the amount of current passing through one of the battery cables with a clamp meter that is rated for more than the number of amps you'd expect to test. Or you could use a shunt battery monitor instead of a clamp meter.

Often the "load" is an inverter with enough devices (such as a series of incandescent/halogen lights until the clamp meter reaches the draw you're looking for. If you're building a 12.8V 104Ah battery, your 0.5C rate would be 52 Amps, so hook enough devices up to the inverter until your clamp meter reads at or close to 52A.
 
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Could something like this double as a capacity tester if set up correctly? I was thinking it might be quite useful to monitor the DC outflow of a system.
That would work the only limitation is the fact that it only has a hundred amp capacity there are larger ones like the victron that'll go 500 or 1000 if you're going to leave it in the system as a constant monitoring I would go with a higher amperage capacity there's also some other brands on Amazon in the $70 range that are decent and I believe they're 350 amp you might check them out but yes that will work well for you just for your test
 
You need a battery tester specifically to do this, like a ZKE. I wouldn't. Put it in a battery, charge it, balance it, and put a load on it and use the BMS read-out as an estimate.
This is how I’d test it, fire up the heat gun, coffee maker, toaster oven and such. Toss the “kitchen sink” at the battery and see how it behaves.

I’d then judge if I’m happy with it or change my design parameters of how they system should be built out.
 
What I typically see people doing to do this kind of test is to hook the battery up to a load and measure the amount of current passing through one of the battery cables with a clamp meter that is rated for more than the number of amps you'd expect to test. Or you could use a shunt battery monitor instead of a clamp meter.

Often the "load" is an inverter with enough devices (such as a series of incandescent/halogen lights until the clamp meter reaches the draw you're looking for. If you're building a 12.8V 104Ah battery, your 0.5C rate would be 52 Amps, so hook enough devices up to the inverter until your clamp meter reads at or close to 52A.
Any BMS worth buying will be able to tell you the current demand of the load, no clamp meter needed.

Again I’m not concerned about getting every Ah advertised but more of having “adequate” capacity with good cell balancing in every day use.

I don’t understand why people get so bent out of shape if the Ah is off by .2-1%.
 
Any BMS worth buying will be able to tell you the current demand of the load, no clamp meter needed.

Again I’m not concerned about getting every Ah advertised but more of having “adequate” capacity with good cell balancing in every day use.

I don’t understand why people get so bent out of shape if the Ah is off by .2-1%.
I am the same way. Crazy how people will buy 280ah cells and have a cow over it pulling 278ah.
 
I am the same way. Crazy how people will buy 280ah cells and have a cow over it pulling 278ah.
False advertising!!! I demand my money back!!! Sham!!!

I think it goes back to the days of buying 280 cells and being able to pull 285-290ah from them.

IMO running load tests on the same bank 4 different ways with 4 different load testers /procedures will get you 4 different results.
 
think it goes back to the days of buying 280 cells and being able to pull 285-290ah from them.
No it's not that, they are over-advertising and under delivering with their cells and being devious or outright deceitful about it.
 
I have purchased 64 cells in Feb 2023, 32 cells in Apr 2022, and 16 cells in Feb 2022. All of the cells came from Docan. The cells were all pristine with no bloating. One of the cells most recent purchased had a voltage variance it was 3.256 volts. The other 63 cells were between 3.304 and 3.306. I do not have a cell tester and do not intend on purchasing one. The amount of work to test 128 cells is more than I would care to do.

I put the cells directly into service. The cells did have issues once the cells reached 3.4 volts. Some of the cells had a higher state of charge and needed to be balanced. I balanced the pack by watching the cells and discharging the cells before they reached the BMS cutoff voltage.

I would have to say that I would purchase from them again even knowing that the cells are probably B grade whatever that means. To me it means nothing at all. The fact that the cells work and work well together and I don't have to mess with them anymore means everything to me. If I kept having runners then I would not be happy. I run the pack between 55.6 volts and 50 volts for the lower cutoff.

I am not going to tear the tops off my cells just to verify that they sanded the QR codes. I really don't care either way what I am concerned with is whether for my application the cells perform up to my standards. My cells are not in EV's so why do I care? If down the road I have issues then I will change my tune, but so far they have exceeded my expectations.
 
I purchased batteries quite a while back from a group buy that later went an undesirable route. Will not explain further. There are many who remember.

Long story short first two batches of cells have done very nicely. Third batch is behaving under the leadership of an active balancer.

There has been a history of bait and switch in this business. Once bitten twice shy comes to mind from a song.

In the end if the buyer is happy that is what counts.
 
So you both are perfectly happy pumping 10 gallons but only getting 9.5 gallons of gas?
You going to buy a racecar and then complain to the manufacture that it wont do the 9 second 1/4 mile they advertise? No, because its still fast as sh*t and they're just going to tell you there is too many variables.
 
Just remember its proven time and time again grade A 280K, BARELY pulls rated 280AH capacity so to think your grade B's will... good luck, and if they do then I suspect they are 304 -re-lasered to appear as 280K.

Plenty of online vendors clearly state grade B if its grade B, they still sell out routinely. No shame in it any more. But actively trying to cover it up, no justification at all.
 

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