CATL 280Ah LiFePo4 Cells -- is this a good deal?

[TheHappyNomads]

I've been wavering between purchasing server rack batteries or going the DIY route. Yesterday I was casually searching up cells on CL in my area and came across what seems to be a stellar deal on (44) CATL 280Ah LiFePo4 Cells manufactured in Fall of 2022. The seller has these leftover from an electric vehicle project and want to get them out of his garage. They come in original packaging and with bus bars. He's willing to sell them all to me for $5400. Seems like a killer deal but after doing some research it also sounds like EVE cells are more reliable/safer in terms of quality??? Is this right or should I snatch these up this weekend? Thanks in advance!

 

[Dzl]

Seems like a killer deal but after doing some research it also sounds like EVE cells are more reliable/safer in terms of quality???

Not exactly. EVE cells are more popular because they are more available to DIY'ers not because they are safer or more reliable. CATL is one of the largest LiFePO4 cell manufacturers in the world, but their market is mainly EV's and other large business customers, they don't officially sell to consumers or small resellers that sell to consumers. So finding good (not grade B or C, not used) CATL cells is harder. Many, probably most cells being purchased by DIYers are not grade A cells. This is true of EVE and even more true of CATL, so what it really comes down to is what is the cell quality, where did the seller source the cells from? Have they tested the cells? and if so, how?

 

[brum]

The price is close to what you can get from China including shipping. Octomber last year I got exactly CATL 280Ah cells with busbars for 135USD/pcs. Prices are lower now. And mine were "grade A" according to the seller, but we all know that this is likely incorrect.

Think about what you'll be doing with 44 cells. You need 48 for 3 16S batteries.

 

[TheHappyNomads]

The price is close to what you can get from China including shipping. Octomber last year I got exactly CATL 280Ah cells with busbars for 135USD/pcs. Prices are lower now. And mine were "grade A" according to the seller, but we all know that this is likely incorrect.

Think about what you'll be doing with 44 cells. You need 48 for 3 16S batteries.

Thanks. I can take a look around. So when you received them how did they test out?

 

[Dzl]

Before you make a decision on your craigslist cells, you should know that Battery Hookup has a deal on CATL cells right now, they are from EV packs, apparently new/unused, and EV grade. Its worth looking into. You can either buy a whole pack (of 20 cells I believe) or in sets of 2 cells.

 

[TheHappyNomads]

Before you make a decision on your craigslist cells, you should know that Battery Hookup has a deal on CATL cells right now, they are from EV packs, apparently new/unused, and EV grade. Its worth looking into. You can either buy a whole pack (of 20 cells I believe) or in sets of 2 cells.

Wow, that looks like a remarkable find. They're recommending leaving them in their module (which I am inclined to agree with) so would these work to use them in a 48v setting without removing a few cells?

EDIT: I'm watching a video from David Poz breaking down this unit to work within a 48v system

 

[brum]

Thanks. I can take a look around. So when you received them how did they test out?

I never tested them out. But other folks ordered from the same seller and at the same time tested them to ~295Ah. Not grade A definitely. But they look to be in perfect condition - totally flat against each other, very close IR. Working for over 7 months now and no complains so far.

 

[MarcoWasRight]

Wow, that looks like a remarkable find. They're recommending leaving them in their module (which I am inclined to agree with) so would these work to use them in a 48v setting without removing a few cells?

EDIT: I'm watching a video from David Poz breaking down this unit to work within a 48v system

If you have the money for 4 modules you can leave all the cells in the module and just cut the bus bars to electrically isolate the last 4. Then put them in a rack. The last 4 cells x 4 rack spaces means you have an extra 16 cells. Bam you got another 48V battery, its just split up into 4 different rack spots. A guy on YouTube has done exactly this and its genius. Makes BMS wiring a little more tedious because you'll have to extend the balance leads and have jumpers connecting cell 4 to cell 5, cell 8 to cell 9, and cell 12 to 13. Either do this with VERY large welding cable (I'm talking 1/0 minimum, might as well go 4/0 to reduce resistance as much as possible) OR you could fabricate copper bus bars using copper bar stock. Then insulate most of the bar stock with shrink wrap (double up if your shelf corners/edges are at all sharp) and your pack will be no different than the other 4 minus maybe a slightly higher IR....you could do the math to figure out how thick your copper bus bars would have to be to equate to a normal aluminum bus bar but I'm guessing it would be pretty thick/wide and probably $50+ per bus bar...no that important to make sure they are 0.1mΩ or whatever...just as long as they are triple or quadruple a normal aluminum bus bar used on the pack. If you aren't pushing the packs very hard (under 0.5C) its not a huge deal anyways....if you have 5 51.2V 280Ah packs I don't know how. you could be drawing more than 0.5C out of them anyways because thats 700A or 35kw of power....that's a lot.

David Poz also did a YouTube video on these modules. You can see how well they are put together. He had to chop out his 4S section. I think he had to cut the bottom metal frame of the module which is hella sketchy but can be done safely....its not NMC so its not going to blow up....just vent some really bad noxious gases and probably catch on fire because you are introducing sparks but it won't be a full on NMC explosion....hopefully.....yeah don't do this one near your house. 16 minute mark

Here's our 4 rack 5 battery genius. The video was posted on another thread here, not sure if the guy in the video is a member here. He made custom shelves but I'm sure you could find something off the shelf (pun not intended)...at 5.5kg a cell you probably need a shelf that can handle the 120kg of the cells plus another 100kg....and then a bit more for safety...so I'd want shelves that can handle at least 300 pounds but preferably 500 pounds.