Samsung 40T and other cells like it?

[rg12]

I think the best rule of thumb for general applicability is to ignore the fictional advertised C-rate completely.

Rely on objective standardised testing only, if high C-rate is important to your use case.

Most people with high powered ebikes can use the 50% of advertised C rate rule and it will work just fine.
Sure it's better to go and dig doing tests and reading forums and articles but most don't have the time or are even interested in doing so, it's only us freaks who get excited by a temperature chart of a cell :lol:

I have peak load 0,9 C = 3A per cell on my ebike 8)

That is too healthy for me

 

[leffex]

Check out VTC5A if you haven't. I came across a graph showing it had higher voltage all the way until emptied @ 20A

Graph here 2,39 in the video:
https://www.youtube.com/watch?v=fZC_bWXrACo

 

[rg12]

Check out VTC5A if you haven't. I came across a graph showing it had higher voltage all the way until emptied @ 20A

Graph here 2,39 in the video:
https://www.youtube.com/watch?v=fZC_bWXrACo

It's a great cell but super expensive to make a profit with through a business so I stick with the 25R

 

[docware]

When you are looking at lygte otherwise excelent data, always also check if there is an asterix at the end of the cell name. If not, the cell was measured at the old clamp, which was not true 4 – wire measurement. Such measurement is always burdened by inaccuracy from the current voltage drop of the clamp transient resistance.



In 2016 Lygte upgraded clamps to true 4 – wire measurement.








Measurements at true 4 – wire clamp is marked by asterisk at the end.



SONY VTC5A is definitely excelent cell, IEC DCIR is 16,3 miliohm at 3,82 - 3,84 V, 25 ± 1°C. Samsung 25R IEC DCIR is 19,5 miliohm at the same conditions.
In the video is 25R without the asterisk, that means 25R is measured at the old clamp. So definitely there is some inaccuracy here. We are not comparing apples to apples.

 

[icherouveim]

Hello,

Some months ago I've read somewhere that the
Sanyo NCR2070C 20700 3500mAh - 30A is an excellent high power cell with a very good life.

Can someone test it to see if it's true?

Of course it has lower capacity but it has smaller size also. Maybe it's a good candidate.

 

[Pajda]

Hello,

Some months ago I've read somewhere that the
Sanyo NCR2070C 20700 3500mAh - 30A is an excellent high power cell with a very good life.

Can someone test it to see if it's true?

Of course it has lower capacity but it has smaller size also. Maybe it's a good candidate.

From my experience I do not see any reason why this particular cell should have very good life. But yes, it is possible. I did not test this particular test because its format, which is not, at least in my opinion, standardized.

 

[rg12]

When you are looking at lygte otherwise excelent data, always also check if there is an asterix at the end of the cell name. If not, the cell was measured at the old clamp, which was not true 4 – wire measurement. Such measurement is always burdened by inaccuracy from the current voltage drop of the clamp transient resistance.

DSC_0281.jpg

In 2016 Lygte upgraded clamps to true 4 – wire measurement.

DSC_2954.jpg

DSC_2955.jpg

DSC_2956.jpg


Measurements at true 4 – wire clamp is marked by asterisk at the end.

asterisk.jpg

SONY VTC5A is definitely excelent cell, IEC DCIR is 16,3 miliohm at 3,82 - 3,84 V, 25 ± 1°C. Samsung 25R IEC DCIR is 19,5 miliohm at the same conditions.
In the video is 25R without the asterisk, that means 25R is measured at the old clamp. So definitely there is some inaccuracy here. We are not comparing apples to apples.

Why do you need 4 wires for?
My DCIR tester has probes with dual spring needles on it and never understood it.
Thanks to you I ordered the aluminum cell holder for testing and it has 4 wires and now that I think about it comes the question for what to do with 4? do I just connect two positives together and two negatives together?
btw, my 25R's always measured between 11 to 13 milliohms at any voltage.
Even tested the IR of a 25R cell that has been working for a year and it still showed 13 milliohm

 

[john61ct]

2 wires carry the power, other two are just for sensing

 

[docware]

I recommend doing small homework and google something like „ four wire measurement , four terminal sensing, …….“ 8)

11 – 13 miliohm … you are measuring ACIR , not DCIR, also recommend some google searching. Your measuring one year running old cell confirms that ACIR is not useful as DCIR is.

I am little bit lazy to explain, so that maybe we can utilize recent discussion here :

http://budgetlightforum.com/node/68976

 

[rg12]

2 wires carry the power, other two are just for sensing

Where do I connect the sens wires and why do I need them if I'm doing a discharge test to see how much current is going through the discharger's current sensor?

I recommend doing small homework and google something like „ four wire measurement , four terminal sensing, …….“ 8)

11 – 13 miliohm … you are measuring ACIR , not DCIR, also recommend some google searching. Your measuring one year running old cell confirms that ACIR is not useful as DCIR is.

I am little bit lazy to explain, so that maybe we can utilize recent discussion here :

http://budgetlightforum.com/node/68976

I noticed by this chart that DCIR is consistently about %50 higher than ACIR so can't I just add %50 to my measurement?
I have this device for measuring:
https://www.aliexpress.com/item/33004789119.html
Any recommendation for an affordable DCIR measuring device?

 

[Hillhater]

You should search a little harder......
https://endless-sphere.com/forums/viewtopic.php?t=94329

 

[john61ct]

4-wire is for accurate sensing of voltage, not current level.

 

[rg12]

4-wire is for accurate sensing of voltage, not current level.

Why do I need separate wires for that if they go to the same place?
What is the difference in accuracy percentage wise?

 

[rg12]

You should search a little harder......
https://endless-sphere.com/forums/viewtopic.php?t=94329

Sorry, I don't understand what you just showed me here, it's the same one I have that turns out is measuring AC and the rest is a conversation about VTC4 cells.

I'm looking for a DCIR meter, something affordable but can't seem to find any dc ones or at least ones that mention that they are either AC or DC.

 

[Addy]

4-wire is for accurate sensing of voltage, not current level.

Why do I need separate wires for that if they go to the same place?
What is the difference in accuracy percentage wise?

Haven't you googled it yet?

https://en.wikipedia.org/wiki/Four-terminal_sensing

 

[john61ct]

4-wire is for accurate sensing of voltage, not current level.

Why do I need separate wires for that if they go to the same place?

Because accuracy of the voltage measurement is reduced by a high current rate.

Greater the rate, less accurate the measurement with 2-wire.

A separate pair for voltage sensing is (should be) standard with high-quality charge sources, much less test equipment.

 

[rg12]

4-wire is for accurate sensing of voltage, not current level.

Why do I need separate wires for that if they go to the same place?

Because accuracy of the voltage measurement is reduced by a high current rate.

Greater the rate, less accurate the measurement with 2-wire.

A separate pair for voltage sensing is (should be) standard with high-quality charge sources, much less test equipment.

Got it, thanks alot

 

[Hillhater]

You should search a little harder......
https://endless-sphere.com/forums/viewtopic.php?t=94329

Sorry, I don't understand what you just showed me here, it's the same one I have that turns out is measuring AC and the rest is a conversation about VTC4 cells.

I'm looking for a DCIR meter, something affordable but can't seem to find any dc ones or at least ones that mention that they are either AC or DC.

Read a little deeper.
Do you have the “mini” or the original version ?

 

[rg12]

You should search a little harder......
https://endless-sphere.com/forums/viewtopic.php?t=94329

Sorry, I don't understand what you just showed me here, it's the same one I have that turns out is measuring AC and the rest is a conversation about VTC4 cells.

I'm looking for a DCIR meter, something affordable but can't seem to find any dc ones or at least ones that mention that they are either AC or DC.

Read a little deeper.
Do you have the “mini” or the original version ?

None, I have the orange one that used to be in the link of the first post.
I rather have a dedicated tester than a charger that has the IR function

 

[Abhineil46]

[/quote]Yes great power discharge rates.

But not great lifespan. 30Q is worse though, per Pajda 40T gets 1000 cycles at 100% DoD with 63% of initial capacity left.

50E is **much** lower power discharge, maximum continuous discharge 2C (9800mA) and 3C (14700mA) not for continuous discharge,

but if that is not critical, can build higher Ah capacity, then with the same test 1000 cycles leaves 85% capacity, may last twice as long!

Note 2.5A charge rate per string is max for longevity.

Also check out LG INR21700H40 
http://queenbattery.com.cn/our-products/764-lg-21700-h40-inr21700h40-4000mah-30a-battery-cell-37v.html
[/quote]

What were the charge and discharge rates for the test for samsung 40t and even 50E for 1000 cycles for above mentioned retained capacity?

 

[HK12K]

Feeling a little A.D.D here, but have a few thoughts because I've been pondering these cells for a future pack build... Mostly just thinking out loud though...

The 80c max cell temperature noted in many spec sheets is the point where irreversible damage is sure to occur, not a recommendation for average use. Mooch, a well respected battery tester, seems to use this number a lot in his testing from what I can recall so i suspect it is based on the cell chemistry. If you're letting your cells get anywhere near this number during use you're pushing them way too hard imo.

These tests are done on a single cell, usually without any external cooling, so we can discern that the 40T will reach 80c with a 35 amp load applied in a free air environment under perfect conditions. That's absolute max before (presumably) immediate damage, so I'd think now would be a good time to apply the 80% rule and stay below 28 amps... in a perfect environment on the bench.

Cram them together in a pack, inside a box, under the sun and they're likely to hit that 80 celsius max at some point under 35 amps. But at what point? Is our self imposed limit of 28 amps low enough? Best bet, I would think, is to use enough of them in parallel where it almost becomes a moot point.

If you've got a 10p pack that's a 350 amp continuous discharge rating per the cell specs. 80% of that is 280 amps. Half that 350 and you've easily got 125 amps continuous on tap without the cells breaking a sweat. I would imagine cycle life would be just fine, but that's just my assumption. This thread has given me a bit of pause though because I would hate to buy 400 of them, ask 200 amps of the pack, only to find it's lost it's luster in only a couple of years. Very curious to learn the results of cycle life testing of gently used cells because I am NOT made of money.

Oh, and disregard "burst" ratings, full stop. There is no such standard and the numbers are very much arbitrary. How long is a burst? .05 seconds? 5 minutes? Without qualification it's just marketing hype. (Advice from the vape community, where thermal runaway can result in facial reconstruction or worse.)

 

[goatman]

Feeling a little A.D.D here, but have a few thoughts because I've been pondering these cells for a future pack build... Mostly just thinking out loud though...

The 80c max cell temperature noted in many spec sheets is the point where irreversible damage is sure to occur, not a recommendation for average use. Mooch, a well respected battery tester, seems to use this number a lot in his testing from what I can recall so i suspect it is based on the cell chemistry. If you're letting your cells get anywhere near this number during use you're pushing them way too hard imo.

These tests are done on a single cell, usually without any external cooling, so we can discern that the 40T will reach 80c with a 35 amp load applied in a free air environment under perfect conditions. That's absolute max before (presumably) immediate damage, so I'd think now would be a good time to apply the 80% rule and stay below 28 amps... in a perfect environment on the bench.

Cram them together in a pack, inside a box, under the sun and they're likely to hit that 80 celsius max at some point under 35 amps. But at what point? Is our self imposed limit of 28 amps low enough? Best bet, I would think, is to use enough of them in parallel where it almost becomes a moot point.

If you've got a 10p pack that's a 350 amp continuous discharge rating per the cell specs. 80% of that is 280 amps. Half that 350 and you've easily got 125 amps continuous on tap without the cells breaking a sweat. I would imagine cycle life would be just fine, but that's just my assumption. This thread has given me a bit of pause though because I would hate to buy 400 of them, ask 200 amps of the pack, only to find it's lost it's luster in only a couple of years. Very curious to learn the results of cycle life testing of gently used cells because I am NOT made of money.

Oh, and disregard "burst" ratings, full stop. There is no such standard and the numbers are very much arbitrary. How long is a burst? .05 seconds? 5 minutes? Without qualification it's just marketing hype. (Advice from the vape community, where thermal runaway can result in facial reconstruction or worse.)

im with you on the A.D.D. and C isn't A. im the same on considering the 40T.

17s4p, is 112 amps. half that is 56 amps half that is 28 amps.

my blue moon max amp is 50 amps but regular use is 30 amps or 7.5 continuous amps per cell of pgroup.

as long as I don't overheat the battery why cant I run upto 12.5 amps through this cell without damaging it.

has anyone done a 10 amp discharge with a fan blowing on the cell?

 

[goatman]

I went to re read to figure out c and a. a 25r 20 amp battery is 8c. so 1c is 2.5amp

if that's the formula and 3c is max discharge for longevity of a cell. 3c is 7.5amps

so 4p of 40T at 3c is 30amps and 16ah and I should get a 1000 cycles if I keep the batteries below 50 but I could rig a fan or divert air to keep the core-temp of battery at 40.

 

[goatman]

this is my thread with my specific question about the 40T
…
the 40T seem awesome as they have great energy density while being rated for high discharge although that I'm not really sure about since I heard they have a short life span so this is the reason of this thread, to find out if there is any truth in that or maybe it was just someone who beat it to max C all the time while that would kill any brand cell.

This was answered in the first three replies.

They may be fine for low discharge usage, but their high C-rate performance only lasts for a short time.

Ughh again...
Nobody but yourself complains here about what has been answer and what's not.

For the third time:

If you want high power density (high C-rate performance) you must accept lower energy density.

A battery that gives better than usual combination of these two opposing factors, will have lower cycle lifespan.

So pick **the one** factor that is most important to you and make a short list

then choose your second more important factor and look for a cell where that factor is "not too bad", do not expect much for that aspect

And accept that the third performance factor will be bad, only able to choose the "least worst".

Rather than asking for good ratings in all three factors, when they each oppose each other.

And of course then a fourth factor, e.g. cost, comes into the picture. . .

I'm aware of all of that but when a respected manufacturer comes out with such a rating for high C rate with high capacity then I look into it and even though it's Samsung I'm still suspicious because I know how stuff works in the real world and that's why I opened this thread.
Seems like Samsung did nothing new here as they just took a 10A cell and rated it at 30A and raised the temperature in the datasheet to a whopping 80C which is obvious this thing ain't gonna last.
I'm still surprised by the super low IR it has out of the box (7 milliohm) but I still wander if I use it at half it's discharge rate for bursts just like I limit customers with the 25R which is my main cell that it will last just as long.

are you considering the 40T a 10amp 4c cell with 4000mah? im running 25rs also. if you are then isn't the 40T better than a 25r? you mentioned 5c destroys a 25r.

by weight a 30q and 40t are equal and you get less with a 25r

 

[HK12K]

Fwiw I just happened upon mooch's retest summary from mid 2018 for the 40T.

"This cell outperforms every 18650 and 20700 in regulated devices at up to about 20A-25A (60W-75W). Only the Samsung 30T hits harder for 21700’s. In my opinion though it is not a 35A battery, as rated in the datasheet.

At 35A continuous this cell reaches almost 90°C. That is too hot to ensure decent cycle life. A rating of 25A continuous brings it to about the same temperature that the Samsung 30T reaches at its rating.

At above 20A-25A (60W-75W) the Samsung 30T is the better performer anyway. The 40T is best at low to mid power levels where it can be the most efficient. The 40T is still an amazing 25A battery though!

If you are running your mod at 60W-75W per battery you will have to try both the 30T and 40T to see which performs better for the way you vape. It’s just not possible to predict.

The two cells I tested delivered 4048mAh and 4062mAh at 0.8A (0.2C) down to 2.5V.

I am estimating this cell’s ratings to be 25A with a temperature-limited rating of 35A (if kept below 80°C) and 4000mAh."