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Li-ion 4.35V: How much do we lose by charging it at 4.20V?
#1
Video 
Hi everybody! I've tested the SANYO UR18650ZTA (4.35/3.7/3.0V) twice - at 4.35V and at 4.20V, which is the charge end voltage for the vast majority of Li-ion cells. The purpose was to find out how much we lose by undercharging a high voltage lithium battery.

As always the cell was bought from Queen Battery and tested with ZKETECH EBC-A20 and a self-made battery holder. It's a PC-connected battery tester supporting 4-wire measuring and discharging at up to 20A.
[Image: 100_9607.jpg]
[Image: 160967_original.jpg]

I've followed all the prescriptions of the IEC61960-2003 standard concerning battery's capacity measurement. Before each discharging cycle each battery was charged at standard current mentioned in its datasheet to charge end voltage (4.2V/4.35V) (cut-off at 0.1A, which is the lowest supported by EBC-A20). Before each discharging or charging i've held a 1-1.5hrs pause. The environment temperature was about 25°C.

SANYO UR18650ZTA

There is the following marking on the tube (traditionally for Sanyo, it's very hard to see): SANYO Z UR18650ZTA V18A.
[Image: 165609_original.jpg]

The main specs from its datasheet:
Rated capacity: 2850mAh at 20°C
Minimum capacity: 2900mAh at 25°C
Typical capacity: 3000mAh at 25°C
Nominal voltage: 3.7V
Standard charge current: 1.45A
Charge end voltage: 4.35V
Charge cut-off current: 58mA
Max. discharge current: 5.8A
Discharge cut-off voltage: 3.0V
Max weight: 48g

Pay attention to the discharge cut-off voltage which is higher than usual and also to the nominal voltage - 3.7V. 4.35V cells' nominal votage usually is 3.8V (4.40V - 3.85V), but not in this case. Max discharge rate is 2C (5.8A) but as you'll see the curves below, it's better not to go behind 5A.

The measured weight is 48.01g:
[Image: 165639_original.jpg]

Test results at 4.35V:
[Image: 165146_original.png]
At 0.2C it's not even close to 3000mAh and it's below the 2900mAh minimum mentioned in the datasheet. At 5A the curve tells us "stop kidding, you've reached the maximum".

Test results at 4.20V:
[Image: 164865_original.png]
At 4.20V this cell becomes a 2500mAh one. The character of the curves remains the same, they are just a bit shorter.

COMPARISON

At 0.2C / 0.58A:
[Image: 164138_original.png]

At 2.0A:
[Image: 164407_original.png]

At 5.0A:
[Image: 164622_original.png]

As you can see at 4.20V charge we lose about 13-14% of the capacity and 14-15% of the energy, but undercharging is a good way to increase the cycle life by hundreds of cycles. And i hope that this test will be useful when choosing between cycle life and capacity.

As usual, i've made the video version of this review too:


Your likes, comments and subscriptions to my channel are highly appreciated! Thanks for reading/watching!
Korishan, cowpen, ozz93666 like this post
XTAR DRAGON 4-slot charger/discharger review: https://youtu.be/S6yVMsIuauE
Miboxer C4-12 4 slot x 3.0A charger review: https://youtu.be/X-ww1YALjvU
Miboxer C2-4000 smart charger/discharger review: https://youtu.be/jrbJceNXv1g

Three High drain 20650 cells' capacity test (Sanyo, LG, QB): https://youtu.be/PExB1qAlxZo
Top 21700 cells LG M50 vs Samsung 48G: https://youtu.be/KGJDogOG4zw
Top 18650 cells 3500mAh batteries' battle: https://youtu.be/fJDuKyXfrQY
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#2
Thanks for the detailed post th,  do keep us informed on how these cells work out from  queen battery ,they do seem a good deal ...

Here's the chart ... 


Important to remember when a cell is considered "dead" after 400 cycles at 4.2v it still works fine , but only at 80% the  capacity it had when new.
 
I would guesstimate at 4.35V you can expect a life around  100 cycles , perhaps 125% of normal 4.2V rated capacity ... this might be worth doing for something like a torch which is only recharged once a month , but for powerwalls a top voltage of 3.93 will get maximum cycle life...

I'm  not convinced there is such a thing as "High voltage" cell ... any lithium cell can be charged to 4.35V , but you will not get many cycles , but the manufacturer can advertise the cell as 2850 capacity(4.35v) , when it's true capacity is  near 2200 (4.2v).

It's impossible to test for what we really need to know ...how many cycles we get when charging to a given voltage ...

We have to assume they will all give the same cycle life when charged to 4.2 ... what would really be helpful  is know the best buy ... how many mAHrs/$ , but only charging to 4.2V..
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#3
Hi ozz93666

Your chart is for a regular 4.20V cell which was overcharged at 4.30V.
UR18650ZTA's charge end voltage is 4.35V, not 4.20, so charging it at 3.93V will increase its cycle life dramatically. But keep in mind that the discharge cut-off voltage is also higher - 3.0V vs 2.75 or 2.5V in case of regular cells.

Unfortunately i can't do cycle life tests, because i'm limited with a single battery testerSad If i had a lab....)))
XTAR DRAGON 4-slot charger/discharger review: https://youtu.be/S6yVMsIuauE
Miboxer C4-12 4 slot x 3.0A charger review: https://youtu.be/X-ww1YALjvU
Miboxer C2-4000 smart charger/discharger review: https://youtu.be/jrbJceNXv1g

Three High drain 20650 cells' capacity test (Sanyo, LG, QB): https://youtu.be/PExB1qAlxZo
Top 21700 cells LG M50 vs Samsung 48G: https://youtu.be/KGJDogOG4zw
Top 18650 cells 3500mAh batteries' battle: https://youtu.be/fJDuKyXfrQY
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#4
(07-12-2018, 10:16 AM)thunderheart Wrote: Hi ozz93666

Your chart is for a regular 4.20V cell which was overcharged at 4.30V.
UR18650ZTA's charge end voltage is 4.35V, not 4.20, 

This is not my understanding from reading the literature ...battery university etc..... 

All 18650 cells are basically the same ...the manufacturers set the standard voltage at 4.2 ... they could have chosen 4.3 , but not enough life .... or 4V too much life and reduced capacity ...

So it's incorrect to say 4.3V is overcharging a standard cell , it's just a trade off , do you want high capacity , or long life ....

I would bet these so called high voltage cells , are just standard cells , the discharge curves have same cutoff point as standard cells , no capacity left after 3V
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#5
(07-12-2018, 11:03 AM)ozz93666 Wrote: All 18650 cells are basically the same ...the manufacturers set the standard voltage at 4.2 ... they could have chosen 4.3 , but not enough life .... or 4V too much life and reduced capacity ...

So it's incorrect to say 4.3V is overcharging a standard cell , it's just a trade off , do you want high capacity , or long life ....

I would bet these so called high voltage cells , are just standard cells , the discharge curves have same cutoff point as standard cells  , no capacity left after 3V

Can't agree with you. There are plenty of variations in chemistry and, for example, a 4.20V cell with 500 cycle is not the same as a 4.40V cell with 400 cycles. The minimum cycle life which manufacturers are trying to hold is 300 cycles, but usually it's 500. If you charge a standard cell at 4.40V you'll never get 400-500 cycles.
XTAR DRAGON 4-slot charger/discharger review: https://youtu.be/S6yVMsIuauE
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Miboxer C2-4000 smart charger/discharger review: https://youtu.be/jrbJceNXv1g

Three High drain 20650 cells' capacity test (Sanyo, LG, QB): https://youtu.be/PExB1qAlxZo
Top 21700 cells LG M50 vs Samsung 48G: https://youtu.be/KGJDogOG4zw
Top 18650 cells 3500mAh batteries' battle: https://youtu.be/fJDuKyXfrQY
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#6
(07-12-2018, 11:21 AM)thunderheart Wrote:
(07-12-2018, 11:03 AM)ozz93666 Wrote: All 18650 cells are basically the same ...the manufacturers set the standard voltage at 4.2 ... they could have chosen 4.3 , but not enough life .... or 4V too much life and reduced capacity ...

So it's incorrect to say 4.3V is overcharging a standard cell , it's just a trade off , do you want high capacity , or long life ....

I would bet these so called high voltage cells , are just standard cells , the discharge curves have same cutoff point as standard cells  , no capacity left after 3V

 not the same as a 4.40V cell with 400 cycles. 

Do the manufacturer say you can get 400 cycles at 4.4V ????   I would believe it if it's in Sanyo's literature , I guess they're fairly reliable . do you have a link ??
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#7
(07-12-2018, 11:29 AM)ozz93666 Wrote: Do the manufacturer say you can get 400 cycles at 4.4V ????   I would believe it if it's in Sanyo's literature , I guess they're fairly reliable . do you have a link ??
It was just for an example.

If you need a specific cell's data, here is another datasheet of UR18650ZTA with cycle life graph, which says it will do 500 cycles at 4.35V charge, 2.9A discharge at 20°C, ending somewhere at 1900mAh at the end of the life.
[Image: cycle-life.png]
The pdf datasheet is attached to this message.


Attached Files
.pdf   ur18650zta---.pdf (Size: 309.08 KB / Downloads: 1)
XTAR DRAGON 4-slot charger/discharger review: https://youtu.be/S6yVMsIuauE
Miboxer C4-12 4 slot x 3.0A charger review: https://youtu.be/X-ww1YALjvU
Miboxer C2-4000 smart charger/discharger review: https://youtu.be/jrbJceNXv1g

Three High drain 20650 cells' capacity test (Sanyo, LG, QB): https://youtu.be/PExB1qAlxZo
Top 21700 cells LG M50 vs Samsung 48G: https://youtu.be/KGJDogOG4zw
Top 18650 cells 3500mAh batteries' battle: https://youtu.be/fJDuKyXfrQY
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#8
(07-12-2018, 11:41 AM)thunderheart Wrote:
(07-12-2018, 11:29 AM)ozz93666 Wrote: Do the manufacturer say you can get 400 cycles at 4.4V ????   I would believe it if it's in Sanyo's literature , I guess they're fairly reliable . do you have a link ??
It was just for an example.

If you need a specific cell's data, here is another datasheet of UR18650ZTA with cycle life graph, which says it will do 500 cycles at 4.35V charge, 2.9A discharge at 20°C, ending somewhere at 1900mAh at the end of the life.
[Image: cycle-life.png]
The pdf datasheet is attached to this message.

from the graph start capacity is 2900 .... 80%of that is 2320 so that gives a cycle life of about 250 at 4.35V ...standard cell gives 200 at 4.3 V 

Although the graph ends at 500 cycles the cell capacity has dropped to 65% original capacity , we must measure to 80% to get cycle life!

So it seems the truth is somewhere between our two positions ...you are correct this is not a standard cell , but the difference is not that great , different additives can slightly change characteristics , but cells are basically the same ...

But there seems no advantage at charging to higher voltage if the capacity Whrs is still only slightly better  than a  good standard cell , but cycle life is nearly halved to 250...

Bottom line must be whrs/$.. for the same cycle life .

Keep up the good work ....great youtube channel ... I'm working my way through your  videos ...oz
thunderheart likes this post
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#9
Completely agree with you. This is an evolution but not revolution. For dramatic increase in capacity, cycle life and discharge current we need a from top to the ground new chemistry.

BTW, high voltage li-ion cells are becoming more and more popular in cellphone battery market but they seem to have no success in cylindrical form-factor. I don't know what's the reason but that's a fact.
XTAR DRAGON 4-slot charger/discharger review: https://youtu.be/S6yVMsIuauE
Miboxer C4-12 4 slot x 3.0A charger review: https://youtu.be/X-ww1YALjvU
Miboxer C2-4000 smart charger/discharger review: https://youtu.be/jrbJceNXv1g

Three High drain 20650 cells' capacity test (Sanyo, LG, QB): https://youtu.be/PExB1qAlxZo
Top 21700 cells LG M50 vs Samsung 48G: https://youtu.be/KGJDogOG4zw
Top 18650 cells 3500mAh batteries' battle: https://youtu.be/fJDuKyXfrQY
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#10
What do you mean by no success? Nearly all recent laptop batteries I've opened up use LiHV cells. My phone (Samsung S7) has a LiHV cell and I'm certainly feeling the capacity drop. Can't get through a full day without recharging.
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