15AH LiitoKala 33140 LFP review and test results

Maast

Maast

Compulsive Tinkerer
Joined
Oct 31, 2019
Messages
769
Location
Washington State
Received 36 cells and 5 cells were either bad or marginal: 3 were completely bad with .021V 1.8V and 2.1V, the marginals had 2.77 and 2.8V - since all the others were 3.0-3.11v (almost all 3.05-3.08V with a few outliers) the marginals had obviously self-discharged and are not something I want to use. A 14% failure rate. The copper tabs were oxidized so these werent new cells right off the assembly line.

I did a capacity test on two cells of 3.65V down to 2.5V at 7A (approx .5C) and one came at at 13.4AH and the other 13.5AH. The battery got warmer than ambient but not by much, I could barely detect a difference by feel.

The copper tabs are the best feature, I found I could solder them with my Weller D550 260W soldering gun with no problem - sand the tabs to bright copper, add a little dab of flux and a drop of solder held on the gun for 30 seconds and then touched to the tabs and it adhered and spread out immediately. I was then able to tin and solder a 12 gauge wire onto the cell. My 100W soldering gun was NOT enough to solder these with.

At $8 bucks they're still a hell of a buy, but just know you're not really buying 15AH cells and they've got a 14% failure rate right out of the box.

Presented below beside a Headway 8AH as a comparison. Positive and Negative aren't marked so I put a black line around one end for the negative.
P1030982.JPG

P1030983.JPG
 
snoobler said:
IR?
Click to expand...
Sorry, not measured and I didnt take down the data to calculate it.

Something I didnt mention in the above: when it took it off the charger it was exactly 3.6v and in two hours when I did the discharge test it'd only dropped to 3.55v which reassured me a lot as to the quality of the cells as charge voltage holding is one of the best ways as a first-pass judge of the quality of a cell.
 
Did another test on a different cell, this time using a shunt based meter. Came out to 14.8 so maybe they actually are 15AH if you do a smaller C rate than the .5C I was doing. Going to call it good enough. Going to test it at a 2C rate next.

By the way, I never mentioned it but they were exceedingly well packed and arrived in only 22 days after ordering.

P1030985.JPG
 
Accomplished another test, this time at almost 2C (28 amps, which drooped to 24a by 2.9v) capacity was exactly 15.0AH and the cell temperature got up to 116F (46.6C).

I've gone from "these are just okay" to "hell, these are pretty good cells!" I owe LiitoKala an apology because I griped at them about the capacity. Still had 5 dud cells though.
 
Last edited:
Did you try to charge the "bad" cells at all? Curious if they took a charge?

Where did you buy them? Link?
 
Finally got the second batch of 41 cells (36 for order and 5 replacements) and every single one was good and tested at 3.185V -+ .01V with one exception that tested at 3.145V. Exceptionally well packed. Did a capacity test and they tested out again at exactly 15AH even at a 2C rate.

Gotta say I'm really liking the copper ends, dead easy to solder as long as you have a soldering gun big enough.

Very happy with the cells, never ordering slowboat again for small orders like this though. 2 months pretty much to the day to arrive.

I think they're a good buy if small cells is what you want.

So far LiitoKala has proven to be a good vendor, wouldn't hesitate to order from them again. Not sure what was up with the duds on my original order but they replaced them at no cost so no-harm-no-foul.
 
Hello Maast,

I am new on this forum, and I am trying to find some information that Liitokala or GuoXuan are not giving for the 33140 LFP cell.
Reading your rewiew, I see that I could use them but, still, some informations are missing for my application.
Could you please tell me if you did it, or could try the following tests?

- 1C Charge,time needed for it,and see if the cell does not warm up too much, 2.5C continuous discharge to 2.5V, average voltage during discharge, final Temp if the cell is not to stressed.
- 1.5C Charge, same discharge test at 2.5C.

it is difficult to buy only one and if I receive a bad cell, it will be a lot of wasted time to get a new one.

I know that you are not here to make everyone's tests, but as you like to share your results, I think these cells are really promising at 187Wh/kg for eV's and RC models...

Best regards,

Vincent
 
Brushman said:
Hello Maast,

I am new on this forum, and I am trying to find some information that Liitokala or GuoXuan are not giving for the 33140 LFP cell.
Reading your rewiew, I see that I could use them but, still, some informations are missing for my application.
Could you please tell me if you did it, or could try the following tests?

- 1C Charge,time needed for it,and see if the cell does not warm up too much, 2.5C continuous discharge to 2.5V, average voltage during discharge, final Temp if the cell is not to stressed.
- 1.5C Charge, same discharge test at 2.5C.

it is difficult to buy only one and if I receive a bad cell, it will be a lot of wasted time to get a new one.

I know that you are not here to make everyone's tests, but as you like to share your results, I think these cells are really promising at 187Wh/kg for eV's and RC models...

Best regards,

Vincent
Click to expand...
Well, 1C by definition is 1 hour, in this case a 15AH cell would require 15A for 1 hour.

As noted above I did a 2C discharge and the cell reached 116F (46.6C) with a ambient temp of 65F. Which is pretty good and they're rated for a 2C discharge. I imagine a 2C charge would result in a near-identical temperature rise.
 
Hello,

thanks for the comments, yes I know that 1c/15A takes one hour, but sometime the charger (Icharger X8 for me) can"decide" to lower the charge current for any reason. I already tested a 32700/6500 Vapcell and it took 1 hour at 1C.
Do you have a PDF showing the 2C discharge capability? They say 75A for 5s , I was expecting 35A continuous because the cell IR at 2-3 mOhms is quite low, if they end at less than 60°c after discharge, I could use them...

Vincent
 
Brushman said:
Hello,

thanks for the comments, yes I know that 1c/15A takes one hour, but sometime the charger (Icharger X8 for me) can"decide" to lower the charge current for any reason. I already tested a 32700/6500 Vapcell and it took 1 hour at 1C.
Do you have a PDF showing the 2C discharge capability? They say 75A for 5s , I was expecting 35A continuous because the cell IR at 2-3 mOhms is quite low, if they end at less than 60°c after discharge, I could use them...

Vincent
Click to expand...
Here's a PDF on the cells, it actually says 5C discharge max but I dont know if I believe that. You're also not supposed to solder it with anything but a laser welder but I did it anyway. Just use a 300 watt + iron and get the drop of solder very hot before touching it so it adheres and spreads before it heats up the innards of the battery.

Edit: just noticed it says 5A as a charge, that can't be right either. For a 15AH cell it should be around 7-10A.
 

Attachments

  • LiitoKala 33140 3.pdf
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Maast said:
You're also not supposed to solder it with anything but a laser welder but I did it anyway. Just use a 300 watt + iron and get the drop of solder very hot before touching it so it adheres and spreads before it heats up the innards of the battery.
Click to expand...
I hear ya. I soldered wires to regular AA Eneloops to make a battery pack for my scanner and you're not supposed to do that either. It does help to sand or file the surface so the solder will adhere quicker like you said. Back in the day I used acid core solder and that would stick to almost anything but it was nasty stuff. And further back in the day when I was a kid my first soldering kit was a Weller gun like yours. But I think it was a 60/100 or close.

Maast said:
Edit: just noticed it says 5A as a charge, that can't be right either. For a 15AH cell it should be around 7-10A.
Click to expand...
If they would be willing to provide the spec sheet from the manufacturer that would be helpful. There might be markings under the PVC wrap that would help identify them. I am curious how close the capacity matches up between the batteries.

I did notice one reviewer mentioned one of his cells leaked so that's something to be aware of.
 
Hello,

yes, I spent hours to find usefull datas on there 15Ah cell, and the ones from Liitokala are not accurate at all, this link shows more realistic numbers

https://www.alibaba.com/product-det...spm=a2700.galleryofferlist.0.0.29ec2d16NmiMr5

If the can be charged at over 1C, and discharged at 3C , it can replace Li-Poly for not to power hungry flying machine, the big drawback is the format and size, but in a Rc Boat, it will be fine.

Reading some short reports: I will have to check if they can be stored for months with no too much self discharge, electrolyte leaks, close capacity and IR. I will order 60, to make 8+7s/1P 15Ah packs, test each cell before making them. as usual , I will not have a BMS, but a balancer cable.
I hope I can get them within 2 months. I will give the test results from dicharge test.

Thanks for your help!(y)
 
Brushman said:
Hello,

yes, I spent hours to find usefull datas on there 15Ah cell, and the ones from Liitokala are not accurate at all, this link shows more realistic numbers

https://www.alibaba.com/product-det...spm=a2700.galleryofferlist.0.0.29ec2d16NmiMr5

If the can be charged at over 1C, and discharged at 3C , it can replace Li-Poly for not to power hungry flying machine, the big drawback is the format and size, but in a Rc Boat, it will be fine.

Reading some short reports: I will have to check if they can be stored for months with no too much self discharge, electrolyte leaks, close capacity and IR. I will order 60, to make 8+7s/1P 15Ah packs, test each cell before making them. as usual , I will not have a BMS, but a balancer cable.
I hope I can get them within 2 months. I will give the test results from dicharge test.

Thanks for your help!(y)
Click to expand...
Good find, I'd go with those. I could tell the ones I got had been sitting on the shelf for a really long time as the copper was quite dark - the same copper color as the pipes in my 21 year old house. But they were cheap so....
 
one more question: what is the exact diameter of these cells? I would like to use plastic holder brackets, but only found 32mm
 
Maast said:
Received 36 cells and 5 cells were either bad or marginal: 3 were completely bad with .021V 1.8V and 2.1V, the marginals had 2.77 and 2.8V - since all the others were 3.0-3.11v (almost all 3.05-3.08V with a few outliers) the marginals had obviously self-discharged and are not something I want to use. A 14% failure rate. The copper tabs were oxidized so these werent new cells right off the assembly line.

I did a capacity test on two cells of 3.65V down to 2.5V at 7A (approx .5C) and one came at at 13.4AH and the other 13.5AH. The battery got warmer than ambient but not by much, I could barely detect a difference by feel.

The copper tabs are the best feature, I found I could solder them with my Weller D550 260W soldering gun with no problem - sand the tabs to bright copper, add a little dab of flux and a drop of solder held on the gun for 30 seconds and then touched to the tabs and it adhered and spread out immediately. I was then able to tin and solder a 12 gauge wire onto the cell. My 100W soldering gun was NOT enough to solder these with.

At $8 bucks they're still a hell of a buy, but just know you're not really buying 15AH cells and they've got a 14% failure rate right out of the box.

Presented below beside a Headway 8AH as a comparison. Positive and Negative aren't marked so I put a black line around one end for the negative.
View attachment 28082

View attachment 28083
Click to expand...
What's the max charge current on these batteries so I no what charger to get. I am look around 4 hours max charge time.

Thanks
 
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