Cycle life tests of High Power density cylindrical cells

[Pajda]

The only problem with the EVE 40P is that I forgot about it when I recently ordered P50B and 50S from Vapcell, also Nkon still doesn't have it in stock. In any case, it's next in the queue.

 

[riba2233]

great to hear, thank you so much you are truly a legend

 

[thermal_runaway]

What do you think about the EVE 40P, it looks like they claim a bit higher current for the 4Ah size? They are not expensive, they could interesting if they have a good cycle life.

I can comment a bit based on my testing, although I'm testing for performance applications rather than cycle life.

Thermals are slightly better than the P42A samples I have, about 45deg temp rise from ambient (25) for 5C. ~3.966Ah on 5C discharge which is quite impressive, my equipment isn't the most accurate but for comparison P42A 5C ~4.032Ah. DCIR 17.67 mOhm (3.6V/3C/10s).

 

[riba2233]

great to hear, thanks!

 

[Pajda]

Thermals are slightly better than the P42A samples I have, about 45deg temp rise from ambient (25) for 5C. ~3.966Ah on 5C discharge.

If I understand well the end temperature on cell body was 70 °C (25+45)? What kind of cell fixture/power connection you have used for the test? I must say that this is similar value what I recently got with Tenpower 40TG in a BF-2A fixture with ambient cooling only, but with welded Cu strips, the end temp goes down to ca 60 °C.

 

[thermal_runaway]

If I understand well the end temperature on cell body was 70 °C (25+45)? What kind of cell fixture/power connection you have used for the test? I must say that this is similar value what I recently got with Tenpower 40TG in a BF-2A fixture with ambient cooling only, but with welded Cu strips, the end temp goes down to ca 60 °C.

Currently using BF-2A for these tests - more direct contact would definitely be better, will probably use welded strips after filtering through our current options.

 

[Pajda]

Molicel P50B and Samsung 50S finally arrived, Cu strips for HP tests already welded, tests started today.

 

[riba2233]

yaaaay, can't wait!

 

[harrisonpatm]

How did you get the copper strips welded to the cells? Did you do that yourself, or did they come that way?

 

[Pajda]

How did you get the copper strips welded to the cells? Did you do that yourself, or did they come that way?

I have unlimited access to a micro-tig technology specifically developed for battery welding, which is very expensive by the way. However, a thicker Ni strip welded using kWeld with a pre-soldered wire would also do the job well.

 

[Pajda]

I relied on the method of frustration composition, i.e. alternating a phase of expectation with a phase of disappointment , and so I started with high power discharge tests. Table data will be available tomorrow.






As for the Samsung 50S, there are no surprises for me. However, since it is not a true HP cell by my standards (it cannot handle 100 % DoD @ 5C discharging with 25 °C ambient cooling up to 80 °C) I will now let it run cycle life test only at 4C.

As for the Molicel P50B, I was little confused for a while, but then I took a look if there is available datasheet. I only found some printsreen version on Aliexpress, where one graph actually confirms my results. There is a claim that without active cooling at 23°C ambient temperature and 100% DoD discharge, this cell can handle only about 30A @ 6C within the 80°C cut-off limit.


If I were to add a conclusion, it would be the idea that it seems that the tab-design limits small cylindrical formats (18650 and 21700) to about 30 A continuous. If we want to go further, it will be very difficult to do it without using tabless design.

 

[Souvlucky]

@Pajda here is the P50B datasheet (source: Queenbattery)

 

[Souvlucky]

Here is also some data from Batemo's test of the P50B:

 

[Souvlucky]

And - sorry for the triple post - a comparison of Samsung 50S, Molicel P45B and Molicel P50B:

 

[riba2233]

awesome stuff, expected a bit more from P50B but still not bad for a 5Ah cell.

also iirc 30T and 45B can do 40A cont below 80C but in any case tabless is huge

 

[harrisonpatm]

I have unlimited access to a micro-tig technology specifically developed for battery welding, which is very expensive by the way. However, a thicker Ni strip welded using kWeld with a pre-soldered wire would also do the job well.

For those of us like me who are curious about the tech/machine, even if we can never afford it: are you able to share more info about it, for those of us who would like to learn more? Datasheet or product description, maybe?

 

[Pajda]

added Table data and update 10C discharge graph with 50S here: Cycle life tests of High Power density cylindrical cells

 

[Pajda]

awesome stuff, expected a bit more from P50B but still not bad for a 5Ah cell.

also iirc 30T and 45B can do 40A cont below 80C but in any case tabless is huge

You are right, it should be that today it is up to 30A continuous discharge for 18650 format (P30B,...) and up to 40A for 21700 (P45B,...) without tabless. I wonder if more competitors in 21700 tabless design format will be available for testing this autumn.

 

[Pajda]

It will probably take me a while to organize the data in the thread into the first posts in a reasonable way.

As for the newly launched tests, they are already running:

P50B:
HE: 0.5C-1C @ 4.15-3.00V
HP: 0.5C-5C @ 4.20-2.50V
HP: 3C-3C @ 4.20-2.50V
calendar ageing

50S:
HE: 0.5C-1C @ 4.15-3.00V
HP: 0.5C-4C @ 4.20-2.50V
calendar ageing

 

[riba2233]

You are right, it should be that today it is up to 30A continuous discharge for 18650 format (P30B,...) and up to 40A for 21700 (P45B,...) without tabless. I wonder if more competitors in 21700 tabless design format will be available for testing this autumn.

I hope there will, we got batteries with Ampace JP40 cells now in new dewalt and milwaukee 8ah packs.

 

[Pajda]

I was wondering if I should get this 8Ah pack because of these JP40s, but I'm worried if these Ampace cells will be ever widely available, like the EVE or Lishen.

 

[riba2233]

Yeah, that is a good question and also for murata VX40 cells that are in similar makita packs. I really hope they will.

 

[thermal_runaway]

Here's something interesting that came up recently, there is supposedly a couple new cells from Samsung earlier this year including the 21700 45T. It seems to just be a juiced up 40T based on the specifications. There is also apparently a "40V" and "50V" out there but I can't find any information.

21700 4500mAh 50A Samsung INR21700-45T Lithium ion How Power Battery 20700/21700 EVVA-High End Lithium ion Battery Expert

EVVA is a professional developer and manufacturer dedicated to providing high end lithium ion power solutions for different applications. With experienced battery experience and advanced technology, it has achieved international high reputation for lithium ion cells supply and battery packs...

evva-tech.com

 

[riba2233]

Makes sense, molicel is so far ahead I was wondering what are the big three doing...

 

[Pajda]

Noticed that Vapcell finally stocked the mass produced EVE 40PL, so I would order samples along with the 40P for tests. I'm thinking about ordering Lishen LR2170LA as well?