Li-ion 4.35V: How much do we lose by charging it at 4.20V?

Original article: https://www.thunderheartreviews.com/2018/08/li-ion-435v-vs-420v-sanyo-ur18650zta.html

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.



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.


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:


Test results at 4.35V:

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:

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:


At 2.0A:


At 5.0A:


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:
[youtube]YcrjKUb3ae4[/youtube]

Check out my YouTube channel for batteries, chargers and other stuff reviews.
In my blog where you can find all my reviews in one place. Every new test/review will be first published on YouTube and in the blog. I'll be happy to see new subscribers, comments, suggestions and just your thoughts.

Did it get hot at 5A? That dip at the beginning is usual for cells heating up.

flippy said:

Did it get hot at 5A? That dip at the beginning is usual for cells heating up.

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I didn't measure the temperature during discharging, but right after it when i was taking the battery out of holder it was quite warm, but not too hot. I wish i had a digital thermometer with logging feature to make temp graphs too, but...

Did you take the test right after charging with the charger indicating 4.20
/ 4.35
or
Did you let the cell rest for a minute or more before the test ?
, which for me results in a 0.3 v or more difference. so in reality a lower real voltage than what the charger shows when I stop the charging.

My newest charger has an option to go above 4.2 volt per cell , and I was wondering who really does that,
do the people who charge to over 4.2 v per cell know that as soon as the charger stops there will be a real lower voltage in the cell and want to get a real close to 100% charge ?
So if a person does charge to 4.3-4.35 volts per cell does the life cycle really go down by that much since as soon as the charger stops and just a couple of seconds later the cell reads more like 4.2 or a little lower ?

ScooterMan101 said:

Did you take the test right after charging with the charger indicating 4.20
/ 4.35
or
Did you let the cell rest for a minute or more before the test ?

Click to expand...

Please read the text carefully:
"Before each discharging or charging i've held a 1-1.5hrs pause."

ScooterMan101 said:

So if a person does charge to 4.3-4.35 volts per cell does the life cycle really go down by that much since as soon as the charger stops and just a couple of seconds later the cell reads more like 4.2 or a little lower ?

Click to expand...

In 1-1.5hrs after finishing charging at 4.35V the voltage goes down to 4.31-4.32V. This is not an overcharged 4.2V cell, this is a 4.35V one.

From 4.35 to 4.31 after 1-1.5 hours rest is impressive. ( 0.04 only drop )

Much better than my Hobby King lipo packs that have been use for a couple of years now. They have a 0.2 drop after a minute or a few seconds even.

I just found out some information from a RC Hobbyist , He says that none of the typical Hobby, Flat Pouch li-po cells are rated for over 4.20 v per cell charge. So it is good to see your find of these " high volt " cells.

I Would love to see more testing , and price comparison of some different brand 21700 cells. I think if I were to change from hobby lipo's the 21700 format is the way to go .

thunderheart said:

In 1-1.5hrs after finishing charging at 4.35V the voltage goes down to 4.31-4.32V. This is not an overcharged 4.2V cell, this is a 4.35V one.

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there is no reason to wait for 21700 when you can buy better 18650's for less money today. especially compaired to those little housefire-in-a-bag-waiting-to-happen hobbyking lipo's.

also: dont charge to 4.2 if you value your batteries, 4.1V or lower if you want to keep them for a long time.


how much capacity do these cells have if you charge up to 4.1V? i would like to see a direct comparison like this to go against a 18650.

ScooterMan101 said:

I think if I were to change from hobby lipo's the 21700 format is the way to go .

Click to expand...

21700 or 18650 is the safe choice. There aren't as many 21700 cells as 18650s but cells like LG M50 5000mAh/10A ($4-5/pc, review) and Queen Battery QB21700 4000mAh/12A ($2.8/pc, review) are worth to pay attention at.

I'll try to test more 21700s in august. This format is getting popular and i think it will replace the 18650 in many applications.
Right now i'm testing two 18650 30A cells. I'll publish the review in a week if nothing goes wrong... Sometimes the software stops responding and it drives me mad when it happens after 5hrs of discharging at 0.2C (+ charging and 1-1.5hr pause), so it turns out that i've lost a whole day... So testing is not the fastest and easiest thing to do))) Plus, i do each test minimum twice to be sure in the results.

P.S. Concerning the voltage drop after charging is stopped: the 4.35V Maxell ICP103450AHR's voltage was dropping to 4.30V after 1-1.5hr pause (review)

thunderheart said:

Plus, i do each test minimum twice to be sure in the results.

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Very good info you are providing about cells, following you on several topics.
Your accent does not appear Russian by the way.

parabellum said:

Very good info you are providing about cells, following you on several topics.

Click to expand...

Thanks!))

parabellum said:

Your accent does not appear Russian by the way.

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It's because I'm Armenian, not Russian I just live in Russia.