Question regarding capacity testing of LTO cells

Claudi

New Member
Dear all,
thanks to Will Prose's great videos regarding LTO cells, I decided to run my photovoltaik plant on 40Ah LTO cells !

So far so good - I have ordered 10 Sets of 24 = 240 cells and now I want to test them before installing them, so that I do not get a buggy cell in my setup.
So I have ordered the cheap (40 US$) aliexpress capacity tester from Wills Video video to chek them one by one.

To be on the safe side I would like to operate them in production between 2.7 and 2.1 volt.
And here my trouble starts: I load one cell up to 2.7 Volt, connect it to the capacity tester and set the low voltage cut off limit to 2.1.

As soon as I turn the discharge amp on (not more than 5 A), the voltage drops down to 2.2 or lower and the test stops immediately. Thats a bit ... annoying

Could you perhaps give me a hint what values make sense for such a cell by cell validation and what limits I should use for test and operation ?

BR
Claudi
 

JimJr

Solar Enthusiast
Check your connections, Those cells (if good) can give a 400a draw at that voltage drop. On a CCA test with copper buss bars (1/8 x 1-1/2 ) can test out at 1600 cca at 2.4v at start per cell .
I have taken my tests 0 v many time and not hurt them . Go use 1.8 v as a end voltage to test the capacity.
 

Claudi

New Member
You were right .... after stabilizing the connection I was able to discharge with 15A ... in less than 2.5 hours per cell !

Is it dangerous (for the cell lifetime) to go down to 1.6 volt instead of 1.8 ?
If I disconnect the cell at 1.6 (15A) and measure the voltage afterwards (without load) it shows 2.0 .. thats ok, isn't it ?
 

JimJr

Solar Enthusiast
I have used lto's for about 5-6 years , I have 18650 lto's that I have purposely shorted out to 0 volts for months at a time. they test to capacity.

I have had the 18650's for 2 years abusing them with over charge to 3v to zero and 0F to 140F and 25C discharge with a cool down period.
The only way I have hurt one lto is to go past 3v with a 65a pouch cell, I accidentally took it 5v . It looked like a balloon , let cool down, deflated it,and discharged tested it. Normally got 125-135 watts but got 450 watts out of it. I notice it had two power areas , one at 1.9v to 2.4 and one at 3.8v to 4.3v . If it wasn't for the electrolyte loss and expansion with the heat, it would have been going farther with it. Since I thought it was toast,
I recharged it to 3v and took it outside and took a 22 rifle and put a few holes in it. Definitely no fun, a got a half inch flame for about a second.
Nothing else but a little smoke-mist .

Going to 1.8v doubt that will hurt them at all
 

Bob B

Photon Sorcerer
I have used lto's for about 5-6 years , I have 18650 lto's that I have purposely shorted out to 0 volts for months at a time. they test to capacity.

I have had the 18650's for 2 years abusing them with over charge to 3v to zero and 0F to 140F and 25C discharge with a cool down period.
The only way I have hurt one lto is to go past 3v with a 65a pouch cell, I accidentally took it 5v . It looked like a balloon , let cool down, deflated it,and discharged tested it. Normally got 125-135 watts but got 450 watts out of it. I notice it had two power areas , one at 1.9v to 2.4 and one at 3.8v to 4.3v . If it wasn't for the electrolyte loss and expansion with the heat, it would have been going farther with it. Since I thought it was toast,
I recharged it to 3v and took it outside and took a 22 rifle and put a few holes in it. Definitely no fun, a got a half inch flame for about a second.
Nothing else but a little smoke-mist .

Going to 1.8v doubt that will hurt them at all
Are the 18650's the only type LTO's you use? What is your application?
 

JimJr

Solar Enthusiast
Most I have are 45 ah Yinlong Cells and other 6ah t0 30 ah cells are being made up for semi truck starting to motor cycle to riding tractor.
The 18650's are cheaper if your are purposely trying to torture them for info first hand . Pouch cells are mainly for stationary - lower C-rates apps , Round cells can handle stationary and vehicle uses at a higher C-rate 10c and higher
 

Bob B

Photon Sorcerer
Most I have are 45 ah Yinlong Cells and other 6ah t0 30 ah cells are being made up for semi truck starting to motor cycle to riding tractor.
The 18650's are cheaper if your are purposely trying to torture them for info first hand . Pouch cells are mainly for stationary - lower C-rates apps , Round cells can handle stationary and vehicle uses at a higher C-rate 10c and higher
Do you have a reliable source to get good ones? ..... most seem to be selling cells that don't meet capacity tests.
 
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