CATL batteries

[Offgrid in Maine]

Does anyone have any experience with the 271ah CATL cells? Got a quote of $74/pc and $500 shipping to Maine. Seller is Senberry.

 

[sisenis]

Just got them - 16 pcs. 271Ah CATL cells from Exliporc. Arrived well packed in polyethylene foam 4 pcs. per box.
Promised to do capacity matching and charged 2$ per pcs. additionally. But didn't submit any capacity test information. Now I'm in dispute with seller.
All terminals scratched and dirty. They explain it by drilling holes, but somehow hard to believe.
Now step by step building the battery.

 

[technerd1988]

Just got them - 16 pcs. 271Ah CATL cells from Exliporc. Arrived well packed in polyethylene foam 4 pcs. per box.
Promised to do capacity matching and charged 2$ per pcs. additionally. But didn't submit any capacity test information. Now I'm in dispute with seller.
All terminals scratched and dirty. They explain it by drilling holes, but somehow hard to believe.
Now step by step building the battery.

Have you capacity tested these yet and IR? I'd like to know because I just ordered the same ones, 8 of them for another huge 12v pack so I'm above 1000 amp hours after these arrive

 

[Gazoo]

All terminals scratched and dirty. They explain it by drilling holes, but somehow hard to believe.

I hope you have informed yourself enough to know no one is getting Grade A cells. More like new old stock. And yes the suppliers do tap the cells terminals if they receive the cells untapped. Some do a better job than others and if your screws are perpendicular to the terminal then your supplier did an awesome job providing the screws go in and out easily.

Lightly sand the terminals using 1000 grit sandpaper. Then blow them out or use a vacuum cleaner to clean the dust created from sanding. Finally wipe the terminals off with rubbing alcohol or acetone. Everyone should do this and most of us have.

Are you planning on parallel top balancing your cells? I am sure you will capacity test them? I would be interested in your results.

I would not start disputing anything until after you have capacity tested your cells. Capacity is way more important than dirty terminals which are very easy to clean. If you expect perfection then you will need to order cells directly from the manufacturer and they will cost a great deal more.

 

[sisenis]

Have you capacity tested these yet and IR? I'd like to know because I just ordered the same ones, 8 of them for another huge 12v pack so I'm above 1000 amp hours after these arrive

I did IR tests only, they shows 0.16 to 0.19mOhms per cell, per specs must be 0.14±0.05mΩ（30~40%SOC) so it's within permitted range.
Not sure my RC3563 IR measurement tool is precise enough, and clamps I have are just simple "crocodiles", so it is quite difficult to get proper measurements with them.

 

[sisenis]

I hope you have informed yourself enough to know no one is getting Grade A cells. More like new old stock. And yes the suppliers do tap the cells terminals if they receive the cells untapped. Some do a better job than others and if your screws are perpendicular to the terminal then your supplier did an awesome job providing the screws go in and out easily.

Lightly sand the terminals using 1000 grit sandpaper. Then blow them out or use a vacuum cleaner to clean the dust created from sanding. Finally wipe the terminals off with rubbing alcohol or acetone. Everyone should do this and most of us have.

Are you planning on parallel top balancing your cells? I am sure you will capacity test them? I would be interested in your results.

I would not start disputing anything until after you have capacity tested your cells. Capacity is way more important than dirty terminals which are very easy to clean. If you expect perfection then you will need to order cells directly from the manufacturer and they will cost a great deal more.

Please see attached some macro photos of terminals. I would point on repeated small dots pattern on almost all terminals. What that could be ?
And viewing on from top, thread drill hole is not centred for some of terminals and after screw in 20mm long studs, some of them are loose even screwed in completely but not tightened.
I've used small drill wire brush to clean the terminals and immediately applied thin layer of Noalox to protect terminals from oxidising.
Honestly saying I'm very tired by doing this setup at my spare time, it took me now 1 month spending 2-3 hours per day. So not decided yet to do or not top and bottom balancing. As again it consumes several hours of setup to assemble then disassemble and days of waiting, more over I believe it's BMS job to do cell balancing. I think more important is cell compression to prolong cells life, and this is next I'm going to solve. Most probably @50% SOC will wrap each 4 cells with reinforced package tape and put between cells 0.5mm PP sheet (PRIPLAK CRISTALINE 000).
Also I'm waiting for REC BMS RS485-USB adapter-cable to arrive, as REC uses 56k baud rate for connection to the BMS microcontroller, and FTDI based RS485-USB adapters I have, doesn't have this baud rate in the driver, and changing baud rate by modifying driver also had no success. So if you are going with REC BMS, buy REC genuine RS485-USB cable.
Attached some photos of my ESS setup.
By the way, seller refund 32$ charged for cell capacity matching, which they didn't do for each of my cell, but for some random one they do.

 

[Gazoo]

Please see attached some macro photos of terminals. I would point on repeated small dots pattern on almost all terminals. What that could be ?

Small dots could be from capacity testing by the supplier. The last photo of the terminal looks nasty.

And viewing on from top, thread drill hole is not centred for some of terminals and after screw in 20mm long studs, some of them are loose even screwed in completely but not tightened.

Mine were loose too, some worse that others. I used a permanent thread locker but still had one strip. Are your studs perpendicular to the terminal?

Honestly saying I'm very tired by doing this setup at my spare time, it took me now 1 month spending 2-3 hours per day. So not decided yet to do or not top and bottom balancing. As again it consumes several hours of setup to assemble then disassemble and days of waiting, more over I believe it's BMS job to do cell balancing.

I am not familiar with the REC BMS. However according to the specs it has .9 amps passive balancing. If the cells are way out of balance you can charge the battery fully, then charge the weak cells up to 3.6 volts or so. You do not need to disassemble your pack to do this. Just be careful with the polarity.

I think more important is cell compression to prolong cells life, and this is next I'm going to solve. Most probably @50% SOC will wrap each 4 cells with reinforced package tape and put between cells 0.5mm PP sheet (PRIPLAK CRISTALINE 000).

Everyone has their own methods for compressing the cells. According to EVE, too much compression can reduce the life of the cell. Considering a 2000 cycle capacity to 80%, the cells will last around 5.5 years if run through a cycle every day. I don't need to be concerned about prolonging the life of my cells because they are used in the event of a power outage. My cells will age out before I can possibly run them through 2000 full cycles. Also keeping the cells between the knees will extend the life of the cells. Of course I will cycle them at least monthly to check them out.

My concern is terminal stress due to expansion and contraction of cells. I am working to resolve that. My fixture consists of .5 inch plywood and threaded rods. I hand tightened the nuts at a full SOC for now. I have some parts on order and will be rebuilding my pack, hopefully one last time.

So if you are going with REC BMS, buy REC genuine RS485-USB cable.

That's good to know.

By the way, seller refund 32$ charged for cell capacity matching, which they didn't do for each of my cell, but for some random one they do.

That's good in a way. But I am still suggesting capacity testing the battery as soon as you can. I don't know what kind of warranty the seller gave you but the sooner you can get this done the better. If your IR measurements are true then that's a good sign. I think I saw another supplier using that same meter. And I noticed in another forum it's as accurate at the more common YR1030 or YR1035+.

Please keep us updated. Thanks.