Sony/Murata US18650VTC4 batteries, “Die, but not today”

I’m adding to my collection of Sony / Murata batteries, and today I’m reviewing a rather old type, the VTC4. As it turns out, they’re still pretty decent, especially if you’re on a tight budget but want a quality battery.
After the jump: tests and a comparison with its closest competitor from Samsung.


At the moment, I know of only one other model in the VTC series with an even lower capacity: the VTC3. Maybe I’ll buy one someday for an experiment. But today it’s the VTC4, a high-current battery with a capacity of 2000 mAh. A quick note about the price.
The title says €2.25, but the product page currently lists several prices depending on the quantity:
Buy 50 times for €2.22
Buy 51 times for €1.62
Buy 300 times for €2.12
Buy 600 times for €2.02

The best deal is for 51 to 300 units: €1.62 each, plus shipping (€12 to my country).



An excerpt from the datasheet: capacity of 2000–2100 mAh (7.4–7.77 Wh), internal resistance around 12 mΩ.


Although this battery series is very old, these batteries were manufactured on May 20, 2018, so they’re relatively fresh.
The positive terminal protrudes slightly above the plane of the casing. I now take this kind of photo as well, just in case it helps identify clones. With Murata, though, it’s easier to check the matrix code, which should be different because it’s unique to each unit.




As always, I started with a “warm-up” run using a regular charger with a capacity measurement function during discharge. The discharge current was 500 mA, with cutoff at 2.8 V. The reading was higher, of course, but that was expected.


Now we can move on to proper testing. This is a high-current battery, so I’ll use a load with currents up to 20 A.


But first, a few words about charging.
The thing is, VTC-series batteries (at least) use a somewhat unusual charging algorithm. They’re charged at 1C for 2.5 hours, then switched to CV mode at 4.2 V. Usually, batteries are charged until the charging current drops below a certain threshold.
My chargers can’t charge batteries this way, but I once checked the difference between the regular mode and the one shown in the graph. The difference wasn’t very large, so I decided to ignore it and stop charging when the current drops to 100 mA.


Charging at 0.5C took 2 hours and 13 minutes. Overall, not bad.


Charging at the rated current of 1C (2 A) took 1 hour and 18 minutes. Then the current dropped to 100 mA and charging stopped, but Murata recommends continuing to charge in CV mode for a little over an hour.


The datasheet includes a discharge graph for currents up to 20 A, with cutoff at 2.5 V. That’s exactly how I’ll test it.


Test results for the first battery at 0.2C (400 mA), 0.5C (1 A), 1C (2 A), 5 A, 10 A, 15 A, and 20 A.

Notice that both the manufacturer’s graph and my results show an interesting feature: at currents up to and including 5 A, capacity in mAh decreases as the discharge current increases, but at 10–20 A it rises. Someone once commented that I was posting impossible graphs and that capacity must always decrease as current increases. Not so: batteries heat up under load, and the delivered capacity can actually increase. The manufacturer’s graph confirms this.


Battery temperature at the end of the test at 10, 15, and 20 A. Looks fine overall.


The second battery’s results are almost identical.


The temperature results are similar.


But these batteries can deliver up to 30 A continuously, so I’ll use the second load and test them with it. First, I fully charged the batteries using the EBC-A20 shown above.


Then, as usual, I first measured the difference between the actual battery voltage and the voltage displayed by the load, applied a correction, and continued the test. In principle, I could apply the correction on the fly, but it was easier for me to turn it off.
In the end, I got 2059 and 2016 mAh.


Unfortunately, they got very hot: the first reached 104 degrees, and the second 107, since it was discharged without pausing to correct the cutoff voltage.


After that, I let the batteries cool down and measured their remaining capacity: 57 mAh for the first battery and 59 mAh for the second.


Excessive heat is very harmful to batteries, so using modes like these is not recommended. The datasheet includes a graph showing how capacity depends on load current and the number of cycles.


While testing the second battery, I started the multimeter's data logger and recorded the discharge curve. The graphs above are certainly prettier, but for now I have to make do with what I have.


Battery resistance after delivery, “conditioning,” and all the tests. You can see that the resistance increased slightly at the end. I suspect the cause was the excessive heat during testing. Ideally, I should have stopped the test, but then how would I know how the battery behaves in different modes...


And, of course, the promised comparison.
For the closest competitor, I chose the Samsung INR18650-20S battery, which has similar specifications.
Their graphs are quite different, so you might think the VTC4 is noticeably better, but that’s not actually the case.
At low current, the VTC4 really does outperform Samsung’s equivalent, but at 10 A the difference in Wh isn’t that great, and at 20 A the VTC4 delivered 100 mAh more, yet their capacities in Wh are the same.

You could say the VTC4 is better overall, but at high discharge currents there’s almost no difference.


And once again, we have an example of high-quality branded batteries. That’s all from me; I hope this information, though rather outdated, was still useful.