New EVE LF280K 16S build from Exliporc

zolee

Solar Enthusiast
Joined
Jan 31, 2022
Messages
42
Some day in February I've ordered 16 cells from Alibaba/Exliporc @107 USD plus shipping from EU warehouse. I was promised brand new, grade A cells.
As I was away for work, I asked the seller to postpone the shipping as much as possible.

So, today I unpacked the cells and made a quick check on them. They where packed in the same heavy thick foam like other have already pictured. It came with just a little surface damage on one pack of four, others where pristine.
They have no bulging visible, on many the shorter side is visible concave, possible to see that on the group shot. If there is bulging, it disappears with a slightest pressure of my hand.

Cell #
Serial #
Date of mfgr
Voltage (V)
IR (mΩ)
C-001​
04QCB76717600JB4S0001234​
25/Apr/2021​
3,2939​
0,20​
C-002​
04QCB76716300JB5Y0004939​
30/May/2021​
3,2937​
0,20​
C-003​
04QCB76717600JB4S0003292​
25/Apr/2021​
3,2938​
0,20​
C-004​
04QCB76717600JB4S0001998​
25/Apr/2021​
3,2928​
0,22​
C-005​
04QCB76717100JB5H0005494​
17/May/2021​
3,2927​
0,22​
C-006​
04QCB76717100JB5H0005448​
17/May/2021​
3,2934​
0,20​
C-007​
04QCB76716000JB5V0005505​
27/May/2021​
3,2894​
0,22​
C-008​
04QCB76717900JB5S0004603​
25/May/2021​
3,2847​
0,19​
C-009​
04QCB76715000JB4N0002018​
22/Apr/2021​
3,2939​
0,21​
C-010​
04QCB76715000JB4N0001276​
22/Apr/2021​
3,2938​
0,21​
C-011​
04QCB76716000JB5V0004986
27/May/2021
3,2078​
0,21​
C-012​
04QCB76716100JB5V0000444​
27/May/2021​
3,2917​
0,21​
C-013​
04QCB76715000JB4N0001086​
22/Apr/2021​
3,2939​
0,21​
C-014​
04QCB76717900JB5S0004050​
25/May/2021​
3,2920​
0,20​
C-015​
04QCB76717500JB4R0001867​
24/Apr/2021​
3,2939​
0,20​
C-016​
04QCB76717500JB4S0005394​
25/Apr/2021​
3,2940​
0,19​

For each cell I've checked the voltages/IR and wrote down the serial numbers, then decoded the manufacture date.

cells.jpg
Here's the group shot.
Behind them are two Kunkin KP184 electronic loads, together with the third one I have in the lab they'll provide 120A (0.43C) discharge current (almost the rated 0.5). Unfortunately, my high power supply is not yet delivered (3.3V 150A) so no charging for me :( I won't even try to charge with 5/10A lab supplies I have. It will take forever, and I have no time for that. I have a 48V/50A PSU, but I don't want to charge them in group, I want to see each one's capacity.

On the right, the pink stuff is silicone baking mat, will use it as cell separator. It's soft, flexible, electrically insulating, rated up to 200°C and it's food grade :)

You may noticed that cell C-011 is bolded in the table above. It's because I found something strange on the venting valve, and I'm not sure how to react. It's probably the reason for "reject" and it's probably only cosmetic, but I'm not sure yet.
c011.jpg
If you zoom in, in the right top corner of the valve is a hole that is not supposed to be there. Tomorrow I'll may try to make a better image and check again.

Coming next: Custom frame for the cells, with spring preload.
 
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LithiumSolar

Solar Addict
Joined
Nov 19, 2019
Messages
119
If you zoom in, in the right top corner of the valve is a hole that is not supposed to be there. Tomorrow I'll may try to make a better image and check again.

It almost looks like something hot touched it and melted a pinhole. Is it just the valve cover or does the actual valve itself have any marks?
 

zolee

Solar Enthusiast
Joined
Jan 31, 2022
Messages
42
It almost looks like something hot touched it and melted a pinhole. Is it just the valve cover or does the actual valve itself have any marks?
I have no idea. Tomorrow I'll take better pictures, and maybe bring it in the lab to inspect it under the microscope.
 

zolee

Solar Enthusiast
Joined
Jan 31, 2022
Messages
42
Possibly a welding Bebe from the welded studs. If so probably not through the foil but just the plastic covering?
That might be. If I take the original phone shot and magnify it, it resembles damage from hot particles. The white around the circle looks like a gas condensate - not dissimilar to the solder blob on cold plastic or metal.

Screenshot_20220409_025011.png
 

zolee

Solar Enthusiast
Joined
Jan 31, 2022
Messages
42
The pack is finally taking some form. In the last few day I worked on/off on the pack construction. Here is the welded frame:
IMG_20220424_154524.jpg
With 3 mm FR4:
IMG_20220424_154819.jpg
I've also ordered some springs that should excert 50 kg each when compressed additional 8 mm from theyre pre-preg state. That would be a maximum 300 kg when cells are full.
IMG_20220424_174753.jpg
Populated the frame with cells. Silicone insulation and FR4 in place.

The wooden end plates are just a place holders. They'll be replaced with something similar to FR-4, but it was a weekend and I needed to check the dimensions. (I had already mistakenly ordered the FR4 bigger than needed).

The damn FedEx still has my charger. It is sitting 100 km from me for almost a week. The FedEx/TNT mess in EU on top of everything going on at the moment is crazy.

In the meantime I've temporarily installed my solar panels on wooden contruction, 12x 385 Wp. Temporarily as the roof needs to be repaired somewhere next year, then I'll install a permanent solution.

IMG_20220421_160602.jpg
4096-1842-max.jpg


My Deye SUN-8K-SG04LP3-EU is also on the way. Maybe it'll arrive in the beginning of may.
 

zolee

Solar Enthusiast
Joined
Jan 31, 2022
Messages
42
Finally got my charger, after a long wait to FedEx to deliver. It's a TDK RKW03-150 3.3V (150A, can be set over 4V if needed).
s-l1600.jpg
This is a photo from ebay, but it is how it looks, except I got all the screws. It definitely needs the sense wires connected and the 5k potentiometer on RV terminal to set the voltage, otherwise it will kick 160A (absolute maximum current) then go to protection after 10 sec.
I fabricated a small adapter board that houses a switch and the potentiometer.

I tried to recreate the conditions in the data sheet as close as possible, so my charging is set to 140A @3.65V and discharge at 120A (3x KP184). I could not justify buying one more KP184 for additional 40A load and I think it was close enough. The result would probably be even worse with 140A discharge.

The procedure was the following:
1. Charge 140A to 3.65V, cut charge at 14A. Wait 60 minutes.
2. Discharge 120A until 2.500V Stop, record results.
3. Immediately recharge the empty cell with 75-100Ah

The discharge results are little bit of a cheating (still disapointing), as each DC load read a little bit different voltages (around 3mV) and that's enough to stop one of them, but other two keep working (@80A) - then the voltage suddenly rise a few 100 mV. This keeps going until the last one sees 2.500V @40A.
I've tried to catch the exact moment the first stop and then stop the rest of them manually - the difference if I let them finish is 2-3 Ah, not more.

Here are the results:

Cell #
Serial #
1st charge (Ah)​
Discharge (Ah)​
C-001​
04QCB76717600JB4S0001234​
179​
278​
C-002​
04QCB76716300JB5Y0004939​
177​
275​
C-003​
04QCB76717600JB4S0003292​
179​
273​
C-004​
04QCB76717600JB4S0001998​
183​
279​
C-005​
04QCB76717100JB5H0005494​
183​
277​
C-006​
04QCB76717100JB5H0005448​
179​
276​
C-007​
04QCB76716000JB5V0005505​
184​
275​
C-008​
04QCB76717900JB5S0004603​
191​
277​
C-009​
04QCB76715000JB4N0002018​
180​
279​
C-010​
04QCB76715000JB4N0001276​
179​
273​
C-011​
04QCB76716000JB5V0004986
237​
275​
C-012​
04QCB76716100JB5V0000444​
181​
273​
C-013​
04QCB76715000JB4N0001086​
179​
276​
C-014​
04QCB76717900JB5S0004050​
176​
273​
C-015​
04QCB76717500JB4R0001867​
179​
277​
C-016​
04QCB76717500JB4S0005394​
181​
281​

Unfortunately the charger arrived a few days after the alibaba protection expired (it should have arrived before the cells if not FedEx), there is no point in complaining that they are not as described. Only one of the cells was able to deliver 280+ Ah.

Top balanced them with a franken-adapter (4x 16 mm2 into one lug) then 35 mm2 to the TDK. The poor PSU needed on average 7.5 hours to charge them to 3.65V. Each set of 4 pulled around 750 Ah until zero current.
2277-1024.jpg

While I was finishing the pack, I hoped that the inverter will also arrive, but it didn't, and I am writing this from the airport.
So, after I top balanced them and fully connected the pack, I had to reconnect the KP184 DC loads, in order to remove some charge. Ended draining 75 Ah in total from the pack.
For some reason the left one is showing much higher voltage, I need to investigate this when I return home. But it did not affect the Ah calculation, in the end all three of them showed the same 25 Ah, 75 Ah in total.
1024-2277.jpg


The cell difference after draining that charge is 39 mV, the culprit is Cell07 (C-010 in my list) which sits at 3.296V, otherwise it would be 1 mV difference. Maybe it had bad contact when top balancing and didn't got as much charge as others, I'll try it again when I'm back home. Otherwise it performed similar to the others, there was no big difference in internal resitstance or charge/discharge performance with others.

Screenshot_20220515_190325.png

BTW, Seplos balance wire for the fartherst cells is a bit short. Watch out when placing the board.
 
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