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Docan 8x EVE 280ah slightly swollen

jay_jay

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Joined
Mar 22, 2022
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Hello everyone,

I just received 8x EVE lf280k from Docan Power. The buying process was pleasant and professional. Had contact with Amy Zheng and Beki and both were really helpful and answered all my questions. Shipping was 6 weeks.
Opened up the packages today and all cells seem to be in good shape. Voltages range between 3.302 and 3.303 between all 8 cells. Manufacturing dates are all December 2021. Visually the cells look brand-new, except they are slightly swollen. I'm not sure whether this level of bloating is acceptable for (assumingly) grade A EVE cells. I also noticed that the swelling is visible in the picture I was sent pre shipment (see first photo). Since I was in the middle of preparing to move I didn't take a closer look at the provided picture.
The other photos are cells 5-8 but 1-4 look the same.
I wanted to start compressing and top balancing today. However, since I just noticed the bulging I would appreciate some feedback from the community. Does it seem like an acceptable degree of swelling or does it mean trouble in the future.
Thought about discharging a bit more before compressing. What do you think?
Best regards
 

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Any chance the cells were exposed to excessive heat during transport?

I would be a bit disappointed however I would move forward to assemble the battery. Since compression is an issue consider assembling them in series under mild compression and restraint. Use wire to connect in parallel if doing the parallel top balance. I would not want to disassemble and reconfigure after the top balance.

Possibly just connect the BMS and put in service and see how it goes. May need to limit charging voltage initially to avoid a cell overvolt. Post the results.

I would still assume the cells are fine and will perform to specification.
 
I just assembled my first battery and none of my cells (purchased from same) looked like that. They all sit next to each other perfectly square.

I'm interested to see how many other opinions come in on this thread as I want to build a few more batteries. The swelling would concern me too.
 
Any chance the cells were exposed to excessive heat during transport?
Not really, temps on delivery day didn't exceed 33°C so probably not an issue.

What do you think about discharging to roughly 30% before fixating?
 
I doubt the cells will suck back in even if discharged to 3.0 volts. I would still be inclined to get them under some compression and put them in service. Yes in service could include a discharge to 30% or even lower while checking if the compression can be snugged up a bit.
 
A slight bulge of the battery is allowed. Because this will not affect normal use, in addition, you need to test the battery: including voltage and capacity. If there is no problem with the detection, you can perform battery compression to reduce the impact of battery bulging in the future. Of course, if you really care about the appearance of the battery, you may need to have a long battle with your battery supplier.
 
in addition, you need to test the battery: including voltage and capacity.
Hi Joanna,
Thanks for the advice. I wanted to start testing but didn't want to build the box and compression before clarifying whether this level of bulging is normal or an indication of something being off. I guess the answer to my case is that it's still acceptable.
Not interested in lengthy disputes with the seller, especially if the cells perform as advertised.
I am going to proceed to build the battery and do some performance testing.
Thanks to everyone
 
One more question:
Since I will build the battery in series (to avoid removing them after top balancing) I'm looking for a solution to connect them in parallel. I have some #2 gauge (35mm2) cable lying around. Thought about buying some sc35-6 terminal connectors and crimping myself some connectors. During top balancing the max current shouldn't exceed 10a (max of my bench power supply). Should be working fine or am I missing something?
 
#12 or #10 wire is plenty for the parallel connections on the 10 amp top balance.
Found some #10 wire that should be sufficient. Just need to get some terminal connectors.
That brought me to another idea, I've got some #2 wire (35mm2) lying around. If I get some terminal connectors couldn't I use it as interconnectors instead of the stiff busbars?
At first glance it should be sufficient. The max amps the inverter (3kw) will draw is roughly 125A (24v system). The #2 wire should be able to withstand 181A when using chassis wiring (source: https://www.powerstream.com/Wire_Size.htm). Since I will secure the inverter with a 150A ANL fuse it should give plenty room for error shouldn't it?
 
Why 150A? IMO #2 can work with 200A.
Don’t forget for inverter losses. A 3k inverter is the output, best to plan for 85% efficiency, that brings you up to 143A, that’s too close to 150 for my liking.

Also many here will say buy a class T fuse.
 
Why 150A? IMO #2 can work with 200A.
Don’t forget for inverter losses. A 3k inverter is the output, best to plan for 85% efficiency, that brings you up to 143A, that’s too close to 150 for my liking.

Also many here will say buy a class T fuse.
You're absolutely right. Haven't thought about losses.
I read somewhere that anl fuses are recommended for lifepo4. After some more digging this seems to be absolutely wrong.
Now I am trying to source a class t 200A fuse in Spain. Someone having a good seller in EU?
 
#2 is good for about 100 amps. Don’t use chassis ground for that kind of current. 2/0 is good for 25 feet round trip at 150 amps with 3% voltage drop and 90 deg C. I would consider Glowing bolts on the chassis a nogo.
 
#2 is good for about 100 amps. Don’t use chassis ground for that kind of current. 2/0 is good for 25 feet round trip at 150 amps with 3% voltage drop and 90 deg C. I would consider Glowing bolts on the chassis a nogo.
Well you lost me there. I wasn't going to ground the chassis of the battery (will be a standard plywood box anyway). The raceway will be max 3 feet. And different sources say #2 gauge will be good up to 180A. E.g. https://www.powerstream.com/Wire_Size.htm
Could you clarify why you think #2 won't be sufficient?
 
This is from your reference page.
“In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account.”

I would discount any wire size chart that doesn’t take all of those parameters into consideration.
Also I challenge you to find a chart that gives you resistance of “chassis” per foot or some kind of calculation that says you can run 150 amps through it and get a specific voltage at the other end.

What you will end up with if you construct as you have planned.
The battery voltage at the battery won’t match the battery voltage at the inverter. The inverter will shut down prematurely on low voltage. The battery won’t fully charge to the set parameters.
 
If you're in the US, shunts.com had good prices last I checked. That's where I got mine.
 
Hello everyone,

I just received 8x EVE lf280k from Docan Power. The buying process was pleasant and professional. Had contact with Amy Zheng and Beki and both were really helpful and answered all my questions. Shipping was 6 weeks.
Opened up the packages today and all cells seem to be in good shape. Voltages range between 3.302 and 3.303 between all 8 cells. Manufacturing dates are all December 2021. Visually the cells look brand-new, except they are slightly swollen. I'm not sure whether this level of bloating is acceptable for (assumingly) grade A EVE cells. I also noticed that the swelling is visible in the picture I was sent pre shipment (see first photo). Since I was in the middle of preparing to move I didn't take a closer look at the provided picture.
The other photos are cells 5-8 but 1-4 look the same.
I wanted to start compressing and top balancing today. However, since I just noticed the bulging I would appreciate some feedback from the community. Does it seem like an acceptable degree of swelling or does it mean trouble in the future.
Thought about discharging a bit more before compressing. What do you think?
Best regards

Yeah those look deformed, but this is typical basen, docan, qso random quality, but on the same token they are cheaper than grade A cells. Perform a test and just hope for the best.
 
Hello everyone,

I just received 8x EVE lf280k from Docan Power. The buying process was pleasant and professional. Had contact with Amy Zheng and Beki and both were really helpful and answered all my questions. Shipping was 6 weeks.
Opened up the packages today and all cells seem to be in good shape. Voltages range between 3.302 and 3.303 between all 8 cells. Manufacturing dates are all December 2021. Visually the cells look brand-new, except they are slightly swollen. I'm not sure whether this level of bloating is acceptable for (assumingly) grade A EVE cells. I also noticed that the swelling is visible in the picture I was sent pre shipment (see first photo). Since I was in the middle of preparing to move I didn't take a closer look at the provided picture.
The other photos are cells 5-8 but 1-4 look the same.
I wanted to start compressing and top balancing today. However, since I just noticed the bulging I would appreciate some feedback from the community. Does it seem like an acceptable degree of swelling or does it mean trouble in the future.
Thought about discharging a bit more before compressing. What do you think?
Best regards

Odd, this is the first time I've heard anyone report a problem like this from Docan. The bulge you are seeing is from someone not paying attention when charging or discharging the cells. If you stick between the recommended voltages (2.5v to 3.65v) you will never get this problem. It doesn't appear too bad, but it certainly indicates someone over charged or over discharged these 4 cells. Probably not by a significant amount, and likely the cells are just fine. Probably best to test them and see if they are able to give full capacity, and then decide if it is worth the effort to send them back. These were probably returned to Docan.
 
Still unable to find a good source for class t fuses. However, I read in a German diy solar forum that a lot of people over there use NH type fuses. AIC 120kA. Are those also suitable or are they all on the wrong track?
Example: https://datasheet.eaton.com/datasheet.php?model=200NHG1B&locale=en_GB

The AIC is indeed what you are looking for, provided all the other parameters are within range. Anything above 25 to 50k amps is what you want. This chemistry can produce some really massive currents if shorted and the resistance is low enough.
 
Well you lost me there. I wasn't going to ground the chassis of the battery (will be a standard plywood box anyway). The raceway will be max 3 feet. And different sources say #2 gauge will be good up to 180A. E.g. https://www.powerstream.com/Wire_Size.htm
Could you clarify why you think #2 won't be sufficient?
I've been using the Blue Sea circuit calculator, it seems pretty accurate and the company has a good reputation. So far, not problems.


I've been using 2 gauge for 150 amps with no problems, although except for surges mine stay under 70-80 amps.
If you have an infrared camera, you will find any problems with ease.
 
Just weighing in to say, got 64 cells from Docan and some of them have a slight budge like the OP.

If I pick four batteries at random and stack them together, they measure exactly 290mm. Which is 72.5mm / cell - at the top end of what the EVE battery specification says they should be 72.0mm +/- 0.5mm.

I'm choosing not to worry about it (what other option is there :LOL: )
 
Probably best to test them and see if they are able to give full capacity, and then decide if it is worth the effort to send them back.
I just finished the 2nd capacity test. Wasn't sure the first time if I got it right but the results were consistent:
- Top balanced to 3.6v
- during discharge the cells stay in between 20mv so well balanced I'd say (BMS balancing disabled for the test)
- discharge until 2.5v disconnect from BMS
Both tries were around 265Ah. Measured with a known and tried battery monitor.
One cell starts running noticeably below 3v. It starts at roughly 2.9v, the cells are +/- 20mv apart. At the point of disconnect, cell #2 reaches 2.5v, the other ones sit comfortably at roughly 2.8v.
That's a rather large deviation at the bottom right?
The AIC is indeed what you are looking for, provided all the other parameters are within range. Anything above 25 to 50k amps is what you want. This chemistry can produce some really massive currents if shorted and the resistance is low enough.
I've been using the Blue Sea circuit calculator, it seems pretty accurate and the company has a good reputation. So far, not problems.


I've been using 2 gauge for 150 amps with no problems, although except for surges mine stay under 70-80 amps.
If you have an infrared camera, you will find any problems with ease.
Thanks for your insights!
Just weighing in to say, got 64 cells from Docan and some of them have a slight budge like the OP.

If I pick four batteries at random and stack them together, they measure exactly 290mm. Which is 72.5mm / cell - at the top end of what the EVE battery specification says they should be 72.0mm +/- 0.5mm.

I'm choosing not to worry about it (what other option is there :LOL: )
Good decision! However, roughly 15Ah missing because one cell drifts heavily annoys me.
However, I'm in contact with Amy from Docan and she seems motivated to find a solution.
I'm really impressed with Docan, great communication, fast replies to my questions and overall very professional. So I would recommend them since I got the impression my case is rather the exception.
But let's see what happens.
 

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