Samsung INR18650-25R cycle test.

[DrkAngel]

#3 test of 5 in series, completed and charted.

Test1: 4.20V >>> 2.50V @ 2.5A (Similar to OEM test voltage) Done.
Test2: 4.20V >>> 3.10V @ 2.5A (electricbike test voltage +OEM high) Done.
Test3: 4.15V >>> 3.10V @ 2.5A (electricbike test voltage, as control) Done.
Test4: 4.15V >>> 2.50V @ 2.5A (electricbike test voltage + OEM low)
Test5: 4.10V >>> 3.30V @ 2.5A (DrkAngel derived optimal @ 1C C\D rate)

(Cell Test # lines are rough guess - properly positioned at average of tests cells, after each test completed)

 

[electricbike]

400 cycles uppdated.

 

[DrkAngel]

They seem to have reached their expected lifespan (80% of initial capacity) at around ~350 cycles. ...
I'm curious about the initial loss trend prior to the beginning of OP's testing, ...

There is no "initial loss trend prior to the beginning of OP's testing".
You seem to have missed the parameters of the testing.
Oem rated capacity is based on a 4.20V \ 2.50V charge\discharge cycle.
OPs test cycle is a much more conservative 4.15V \ 3.10V charge\discharge cycle.

Subsequent test series is determining capacity at various charge\discharge cycle ranges.
Oem C\D cycle range "cell test 1" shows 102% 0f rated, OPs C\D cycle range "cell test 3" shows 88% 0f rated ... same cell = same actual capacity!

2nd test series preliminary results interestingly shows ...
2.50V to 3.10V appears to contain <8% of total capacity
(155% discharge depth = 108% capacity)

 

[DrkAngel]

Was able to chart multiple capacity profiles. (discharge)
The .2A profile should be very close to the actual resting (static) voltage profile.

Pattern similarities seem to confirm the validity of .2A discharge map using manufactures discharge curve as source data.

 

[DrkAngel]

I see your capacity map shows a lot of energy held above 4.15V, thanks for the update.

Capacity map shows ~8% capacity between 2.50V and 3.10V then ~6% capacity between 4.15V and 4.20V.

 

[madin88]

its really great to see such tests and graphs beside all the theoretical presumptions. Thanks guys!
looks like the 3,1V - 4,15V range seems to be sufficient enough for long lifespan, but im really looking forward to the result of the 3,3-4,1V test.
it would be nice to see how the 25R performs at higher discharge currents like 5-10A, because this is the range where this cell normally is used.
any chance to do such?
or would it be possible do do it like:
1/3 of the time with 10A
1/3 of the time with 5A
and 1/3 of the time with 2,5A


@ DrkAngel
in the excel sheet it looks like the current rises slowly after the start and the 2,5A do not flow until 4V undershoot.
is this normal because of the voltage drop?

 

[electricbike]

its really great to see such tests and graphs beside all the theoretical presumptions. Thanks guys!
looks like the 3,1V - 4,15V range seems to be sufficient enough for long lifespan, but im really looking forward to the result of the 3,3-4,1V test.
it would be nice to see how the 25R performs at higher discharge currents like 5-10A, because this is the range where this cell normally is used.
any chance to do such?
or would it be possible do do it like:
1/3 of the time with 10A
1/3 of the time with 5A
and 1/3 of the time with 2,5A

I need to finish the ongoing tests first, maybe after that i can do some other test.

 

[neptronix]

mm.. let's see you do 100% SOC instead of 80%-90% SOC.
I saw one spec sheet for this cell where at 100% SOC cycles, the battery is down to 60% capacity after something like 200/300 cycles :/

 

[Ohbse]

mm.. let's see you do 100% SOC instead of 80%-90% SOC.
I saw one spec sheet for this cell where at 100% SOC cycles, the battery is down to 60% capacity after something like 200/300 cycles :/

Yes, you're correct. At 100% SOC cycles with near maximum current in both discharge and charge you're going to have a very lackluster lifespan, however if that's how you're actually using the cells then you've definitely missed the memo on designing a battery suitable for your requirements. The tests being done here are far closer to real world than smashing the cells. We all know abuse will result in damage...

I've done several hundred partial cycles on my LG HE4 pack, level of degradation is very, very low. If I had cheaped out and bought *just* enough cells to achieve my desired range I would probably be disappointed by now.

 

[zener]

It would be interesting to see the comparison from this cycle test to the same cycle test but with a 3 hour charge time instead of 1 hour.

 

[neptronix]

Yes, but by only using 80-90% of the pack, you are lowering it's effective whrs/kg, negating the positives of these cells.
You make a 20ah pack into a 16-18ah pack at the end of the day, and that's where you start at, so after a few hundred cycles, you're down to a 12-15 AH pack capacity.. that's a big gotcha that should be considered.

I mean, that's the case with any battery.. it's just that it's very pronounced here, and even the cherry picked scenario looks bad.

mm.. let's see you do 100% SOC instead of 80%-90% SOC.
I saw one spec sheet for this cell where at 100% SOC cycles, the battery is down to 60% capacity after something like 200/300 cycles :/

Yes, you're correct. At 100% SOC cycles with near maximum current in both discharge and charge you're going to have a very lackluster lifespan, however if that's how you're actually using the cells then you've definitely missed the memo on designing a battery suitable for your requirements. The tests being done here are far closer to real world than smashing the cells. We all know abuse will result in damage...

I've done several hundred partial cycles on my LG HE4 pack, level of degradation is very, very low. If I had cheaped out and bought *just* enough cells to achieve my desired range I would probably be disappointed by now.

 

[electricbike]

Any chance to test a VTC5 after this?

I only have some INR18650-25R left to do the last tests, no VTC5.
If i had some of those VTC5 i could do the same test, no problem if someone could send some.

 

[giblet]

Any chance to test a VTC5 after this?

I only have some INR18650-25R left to do the last tests, no VTC5.
If i had some of those VTC5 i could do the same test, no problem if someone could send some.

Any chance you could update us as to when you expect more 18650 batteries and when packs will be available from your website... I've finally bought a drive from TangentMotors after lurking and using this forum for about three years and now your recommended batteries aren't available

Gotta laugh. Just have to wait a bit longer I guess...

 

[electricbike]

Any chance to test a VTC5 after this?

I only have some INR18650-25R left to do the last tests, no VTC5.
If i had some of those VTC5 i could do the same test, no problem if someone could send some.

Any chance you could update us as to when you expect more 18650 batteries and when packs will be available from your website... I've finally bought a drive from TangentMotors after lurking and using this forum for about three years and now your recommended batteries aren't available

Gotta laugh. Just have to wait a bit longer I guess...

Hmmm... if you meaning me i don't sell batteries :?

 

[giblet]

Hmmm... if you meaning me i don't sell batteries :?

Sorry - not the person I thought you were No worries. Nice work BTW.

 

[DrkAngel]

its really great to see such tests and graphs beside all the theoretical presumptions. Thanks guys!

@ DrkAngel
in the excel sheet it looks like the current rises slowly after the start and the 2,5A do not flow until 4V undershoot.
is this normal because of the voltage drop?

Voltage "sag" is an omnipresent factor in all battery types.
"Sag" is a factor of Internal Resistance x discharge rate = heat, (rather than output voltage), production
The higher the discharge rate ... the deeper the sag.
Voltage sag is directly relateable to waste heat production!

Note the depth of initial sag at various discharge rates and the corresponding rise in heat production.

Note that the 1C and the 8C (20A) line output the same 2500mAh.
"How could they output the same usable energy if the 8C is producing so much more waste heat?" you may ask.
Well, simply, they do not.
While they both tested at 2500mAh output ...
at 1C - 2500mAh x 3.6V (average discharge voltage) = 9Wh usable output
at 8C - 2500mAh x 3.25V (average discharge voltage) = 8.125Wh usable output (90% usable output vs 1C)

Danger - higher output rates produce dangerous heat levels!
Severe burns are possible, hot enough to cook eggs, meat, fingers etc,
Active cooling recommended!

 

[zener]

It would be interesting to see the comparison from this cycle test to the same cycle test but with a 3 hour charge time instead of 1 hour.

Yes, indeed.
It would be cool to see how much extra cycles to expect when charging slower.

 

[DrkAngel]

.3C charge discharge cycle might take 8 hours.
500 cycle test would take 4000 hours = 166.6days about half a year!

Test device requires same charge\discharge Amps ... IIRC.

I would recommend more productive, or at least less time consuming, tests.
Using present data I will refine my recommended test voltages for optimal capacity-lifespan.
3.20V >> 4.12V @ 2.5A might be more optimal? ... Analyzing data.

 

[zener]

300 cycles even 200 cycles would be enough to see the line of expectation.
2 hours more per cycle would sum up to 600 hours 23 days more for valuable data.

 

[electricbike]

Test device requires same charge\discharge Amps ... IIRC.

Actally, at a closer look it seems that the reaktor can do different charge/ discharge current.
So no problem to do for example charge 0,5C and discharge 1C

 

[Offroader]

h0tr0d wrote: Ok then,
2C charge/discharge, 4.1V - 3.3V?

Sure, no problem, i will do that when the chargers arrive.
Edit: Actually Samsungs spec say no more than 4A in rapid charge.

Just wondering here, shouldn't we keep things consistent for comparison purposes and try 4.1v to 3.3v at 2.5A?

By changing the charge/discharge values and also the voltage range, we won't be able to compare exactly what made any difference.

I would like to see a 4.1 to 3.3v comparison to 4.15 to 3.1 volts because this is something we all need to decide on what is the best voltage range to charge and discharge to.

Further tests with changing the charge and discharge rates should then be made.

 

[DrkAngel]

#3 test of 5 in series, completed and charted.

Test1: 4.20V >>> 2.50V @ 2.5A (Similar to OEM test voltage) Done.
Test2: 4.20V >>> 3.10V @ 2.5A (electricbike test voltage +OEM high) Done.
Test3: 4.15V >>> 3.10V @ 2.5A (electricbike test voltage, as control) Done.
Test4: 4.15V >>> 2.50V @ 2.5A (electricbike test voltage + OEM low)
Test5: 4.10V >>> 3.30V @ 2.5A (DrkAngel derived optimal @ 1C C\D rate)

"Test4: 4.15V >>> 2.50V @ 2.5A (electricbike test voltage + OEM low)" seems to be unnecessary, the 4.15 >>> 4.20V capacity is already determined. _ if test not already started.
For direct comparison ... I would like to substitute a Test4: 4.10V >>> 3.10V @ 2.5A 5 cell capacity run
Otherwise the "Test5: 4.10V >>> 3.30V @ 2.5A " has no base of reference.
After graphing up the discharge capacity profiles I would like to ...
edit Test5: 4.10V >>> 3.20V @ 2.5A (DrkAngel derived optimal @ 1C C\D rate)

 

[zener]

My suggestion for next cycle test's: (maybe cut @ 300 cycles)
Test5: 4.10V >>> 3.20V @ 2.5A (DrkAngel derived optimal @ 1C C\D rate)
After Test5:
Test6: 4.10V >>> 3.20V @ 2.5A / 0.83A (zener (want know howmuch slower charging impacts cycle life) @ 1D 0.33C rate)

 

[electricbike]

I have not started with test 4 so i will jump to test 5 instead soon.

 

[DrkAngel]

New recommended test schedule
Tests 2-3-4 will determine capacity to 4.20V >>> 4.15V >>> 4.10V
4.10V is reputed to double cycle life vs 4.20V.
Lower, is reputed to extend life further, but at the loss of a large capacity bulge just below 4.10V so, not advisable?
I altered my recommendation of discharging to 3.30V, to 3.20V, due to the 1C discharge graph indicating a fair bulge of capacity below 3.30V.

Test1: 4.20V >>> 2.50V @ 2.5A (Similar to OEM test voltage) Done.
Test2: 4.20V >>> 3.10V @ 2.5A (electricbike test voltage +OEM high) Done.
Test3: 4.15V >>> 3.10V @ 2.5A (electricbike test voltage, as control) Done.
Test4: 4.10V >>> 3.10V @ 2.5A (new recommended Test4:)
Test5: 4.10V >>> 3.20V @ 2.5A (DrkAngel derived optimal @ 1C C\D rate) discharged voltage altered to 3.20V