Just bought a stack of these Liitokala 15AH, guess I'll see how good they are

[Maast]

Bought a stack of these on Aliexpress to even up the mismatched capacity of my BYD packs. According to online reviews their smaller ones are testing out close to capacity so I thought I'd take a gamble - that and how inexpensive they were seem worth it. When you buy 8 it works out to something like $8 a cell.

Guess I'll see how it goes. The solderable copper connecting ends are what caught my eye

 

[Supervstech]

I guess from the number scale these are FAT short cylinders, 33mm wide, and 140mm tall... odd size, compared to an 18650 that would be about 3Ah, not sure how that size could be 15Ah...

 

[Supervstech]

Ok, so a little taller than 2 18650’s and a little less than twice as thick, so big cells. I see now.

 

[Jan Broz]

Did the cells already come? How are they?

 

[Maast]

Not yet. They state 20-38 days to deliver. You can get anything cheap on Aliexpress, but the tradeoff is how bloody long it takes to get here - unless you pay for express shipping and then it's not cheap anymore.

 

[ericgrand]

I will follow your thread as this format together with the high C rate is exciting.
I was considering 32700 format to rebuild a electrical vehicle battery pack, especially the ones with threaded connection, but this format seems to be more efficient.
What kind of busbar do you anticipate, and how do you plan to get it soldered?
Large LFP cells does not seems to be compatible with high C discharge rate (above 1C), while the smaller cells seems Ok.
And if one 1 fail, it is cheaper to replace just one small instead of a large one!

 

[Maast]

I will follow your thread as this format together with the high C rate is exciting.
I was considering 32700 format to rebuild a electrical vehicle battery pack, especially the ones with threaded connection, but this format seems to be more efficient.
What kind of busbar do you anticipate, and how do you plan to get it soldered?
Large LFP cells does not seems to be compatible with high C discharge rate (above 1C), while the smaller cells seems Ok.
And if one 1 fail, it is cheaper to replace just one small instead of a large one!

I can't speak to a EV battery pack - never considered it, but my thought on using a hundred smaller cells paralleled together is a hundred points of failure. I'm sure you can achieve the necessary C rates using larger cells. Four 100AH cells with a .5C spec still gives you 200A, etc. My other thought would be that these round cells arent very volumetrically efficient because of all the airspace they leave between them. But that may be a good thing for cooling the cells under high C rates. Like I said I've never really given it much thought. I can see the round cells being useful in making a electric bike pack since they have to be odd shapes to fit inside the frame.

As far as soldering goes I'm not using bus bars, I'll be attaching 12 gauge leads using a micro torch.

With that much of a heatsink I'll need a lot of concentrated heat to get it hot enough to melt the solder fast so I can remove the heat before it spreads and cooks the cell. A smaller source of heat will take longer heating up the spot giving the heat time to spread out and damage the cell.

 

[Maast]

Received and reviewed the cells, mildly dissapointed but it's not a disaster. Still a good value.
https://diysolarforum.com/threads/15ah-liitokala-33140-lfp-review-and-test-results.14922/

 

[Maast]

Did further testing using a better AH meter, they're a full 15AH even at a 2C rate. Rather like them and am ordering another 36.

 

[upnorthandpersonal]

Funny, the name 'Liitokala' means 'Flying fish' in Finnish. Wonder where they got that from.