Sony VTC6 batteries: high-current test

Somehow, I’ve ended up preferring to buy batteries from Gearbest. Over the years, I’ve bought a really large number of them. I’ve had a problem only once, when two packages went missing at the same time. After 60 days, they refunded me without any questions, since the tracking showed that the packages hadn’t even entered the country.
This time was no different: I ordered 80 cells, half for me and half for a friend.

The price in the title is for a lot of 4 batteries and a case.

These are 18650-size batteries, model VTC6.
Rated capacity: 3000 mAh
Maximum continuous current: 15 A without temperature monitoring, or 30 A if the maximum temperature is limited to 80 degrees.
Link to the full datasheet

As I said, half of the 40 cells are already here, and I’ll test some of them today.


The package was shipped via Azerbaijan Post, which is odd, since the last few times it was delivered by Nova Poshta. Note that shipping costs extra: 2 lots + 44 cents, 3 lots + 22 cents, 4 lots + 12 cents. Shipping is free if you order 5 lots or more, which is what I did.
Delivery was really fast, about a week and a half, but the packaging was worse this time. Only my batch was damaged, though; my friend received everything in perfect condition. Three of my five boxes were broken.


The second batch fared much better: only one of the five packages was damaged.
I received it after writing the review.


The batteries look quite familiar. The positive terminal is flat, almost flush with the casing.


Besides the warning “Danger do not use outside of battery pack,” there’s also this marking:
SE US18650VTC6
K C6A13YF25J


The first part of the marking is clear enough: it’s an 18650-size battery. Let’s try to decipher the second part, with the help of this table from the battery manufacturer.
How to determine the production date of Sony batteries.
K - manufacturer: Sony
C6 - size code: 18650
A13 is irrelevant here; it’s an internal code.
Y - year of manufacture: A = 92, B = 93, and so on. So Y means 2016.
F - month of manufacture. Same idea as the year, but counting months: F is the sixth month, June.
25 - simply the day, in this case the 25th.
J - I’m not sure what this means. It says “electrode history,” but the marking system is the same, with letters assigned in alphabetical order.

So the batteries were made on June 25, 2016. Today is June 27, so they’re almost a year old :)


These are the batteries from the second batch, ordered a little later.
This batch has a more recent production date: September 6, 2016.


The dimensions are almost as specified: the length is spot on, while the diameter is slightly larger.
All the batteries weigh the same, which also points to them being genuine.


The first test was done in my universal charger. The discharge current was 500 mA, which is close to 0.2C; the datasheet specifies capacity at this current. The only problem is that the charger discharges only down to 2.8 V, not 2.0 V, which the batteries can handle.
By the way, the batteries arrived quite heavily discharged. During the first charge, about 2600 mAh “went in.”
I got about 3250 mAh out, which is excellent, if you ask me.


To get a more accurate result, I decided to connect them to an electronic load that also works as a battery analyzer.


I don’t usually test internal resistance, but it’s been mentioned so many times that I decided to post the results.
The batteries above were labeled 1 through 4; I then tested numbers 2 and 4.
Internal resistance measurement, battery number 2, at 1 A and 10 A.


The first test was at 3 A (1C), down to 2.0 V.
Discharged: 3080 mAh, 10.81 Wh
After that, charging put back 3071 mAh, 12.03 Wh.

Don’t be surprised that the capacity in mAh is higher during discharge than during charging. This is perfectly normal for lithium batteries. What matters here is the capacity in Wh, and the difference is the battery’s “efficiency.”


Battery number four.
Discharged: 3109 mAh, 10.89 Wh, almost the same as the previous cell. These batteries are well suited for connecting in series, since they have identical specifications.


Here, I decided to run two tests at once. More precisely, I ran a test and debunked one of the myths.
I often come across claims and advice online saying that a new lithium battery can be "broken in."
Here’s how I ran the test:
1. Take the battery out of the package. It’s about 25% charged, so put it on charge.
2. Once charged, discharge it at 10 A (this is the actual test) down to 2.5 V.
3. Charge it again using the same settings as the first time.
Capacity: 2980 mAh, 9.914 Wh


4. Discharge it at 3 A down to 4 V. This is necessary to ensure the next part of the test runs correctly.
5. Top it up to full charge as in the previous test.
6. Discharge it at 10 A down to 2.5 V.
7. Charge it fully as in the previous test.
Capacity: 2980 mAh, 9.936 Wh.

In the end, the capacity in mAh was exactly the same, while the Wh figure increased slightly. But I wouldn’t call 0.2% any kind of increase; it’s more likely measurement error.


I took a thermal image at the end of each test, and the results were identical here too.


But let’s get back to the datasheet.
It says the battery can be discharged at 15–30 A, but at 30 A you must monitor its temperature.



I decided to try discharging it at 20 A.
I could, in theory, discharge it at up to 33 A—that’s the maximum current for my electronic load. But the continuous discharge current for these batteries is 15 A, so even 20 A is outside the normal operating range. This was more of an experiment, especially since I’m not sure how good the holder is.
I charged the battery according to the specifications for lithium batteries, stopping the charge at 4.2 V when the current dropped below 1/10 of the charging current.
I set the load to shut off at 2.5 V, with a load current of 20 A (twice the value shown on the display).


About two-thirds of the way through the discharge, the battery temperature exceeded 80 degrees, so I paused the test for a while. By then, the battery had delivered almost 1800 mAh.
Once the battery had cooled to an acceptable temperature, I resumed the test. The final result was 2774 mAh, which is quite good at this current.


The thermal image shows the battery temperature when I manually stopped the discharge, and its temperature at the end of the test.


I decided to discharge two more batteries at 15 A, this time without monitoring the temperature. In other words, come what may.
The first battery was charged with a basic charger, and the second with the electronic load. The difference in the readings is because the first battery was charged using a basic charger, while the second was charged using the electronic load I’d used to test them earlier.
In any case, the results are quite good: 2976 and 2872 mAh at a discharge current of 15 A and a cutoff voltage of 2.5 V.


Here are a couple more thermal images. The first was taken about halfway through the test, the second right at the end, just before cutoff.


You’ll probably ask why I didn’t discharge them down to 2.0 V. I did try, but only as an experiment. According to the datasheet, the cutoff voltage at discharge currents of 10 A and above is 2.5 V, not 2.0 V.


In my opinion, the batteries passed the test just fine, and I consider them suitable for use in both power tools and e-cigarettes.
The manufacturer also specifies discharge currents of up to 80 A for no more than 6 seconds, and up to 19 seconds at 55 A.
These are peak ratings, but they still show that the batteries can handle heavy loads. The only batteries I know of so far that allow a 100 A discharge for up to 1 second are the Samsung 25R.


Overall, I think these batteries are perfectly good. I bought them for about 24.99 for four; the current sale price is 25.99, which isn’t much more.

That’s all. I hope you found the review useful.