Popular Panasonic NCR18650B protected batteries

I buy quite a lot of batteries. This review covers just 16 of the 40 I ordered: some went to a friend, and I kept the rest.



I bought them in lots of 8, which worked out a little cheaper. These days, buying 4 at a time is slightly cheaper. I buy them regularly and in large quantities, usually in batches of 20–40. You can find more tests in this review.

To avoid any trouble with customs, I ordered one lot at a time, just to be safe.
They come packed in sturdy cardboard boxes. They used to be shipped in simple plastic bags, but after several complaints the store changed the packaging, and delivery problems have stopped.


Using the table for determining the production date of Panasonic batteries, I found that these were made in early September 2016. I wouldn't call them brand new, but they certainly aren't old either. Besides, the weather has warmed up now, so there's a much lower chance they'll have to travel through freezing temperatures on the way here.


The batteries were made in Japan, at least according to the marking on the casing under the protective wrap.
A protection board is fitted at the negative terminal, and a strip runs along the entire casing to the positive terminal. The brands themselves don't make protected batteries; third-party manufacturers add the protection. For branded batteries (Samsung, Sanyo, Panasonic), though, this is handled by trusted specialist companies.


Since these batteries have protection, they're noticeably longer: 70 mm instead of 65 mm. Be sure to take that into account.
The diameter is also slightly larger, but the wrap isn't very thick (it's needed to fit the protection board), so the difference here is smaller.
The batteries weigh about the same, at 48 grams.


As usual, the first test was done with a universal charger. It measures capacity during discharge, but tends to overstate the result a little. Opus-type chargers suffer from the same issue.


To get more accurate results, I ran the remaining tests with a battery tester, although essentially it's just a type of electronic load.

First test: battery No. 1, capacity 3198 mAh or 10.72 Wh.


Second test: battery No. 4, capacity 3188 mAh or 10.76 Wh.
Considering the battery was discharged to 2.8 V, even though its minimum voltage is 2.5 V, that's perfectly normal.



During the test, I learned the hard way about the issue I mentioned above. Because the battery was longer than usual, I accidentally damaged it while trying to shove it into the test holder. The strip from the positive terminal touched the metal contact in the holder, and I punctured the insulation.
There was a bit of smoke, but the battery itself was unharmed. It is, however, now "unprotected."


You can see where the insulation melted. It eventually melted along the entire length; perhaps the short circuit happened near the negative terminal, but it's hard to check now.


The protection board is standard: a DW01 controller IC and a pair of MOSFET arrays. Some cheap batteries have only one transistor on the protection board, which limits the maximum current. That's not an issue here.


But as they say, every cloud has a silver lining: now I can test the battery more realistically, without the limitations imposed by the protection board.
First, a test at a discharge current of 1C. The battery's rated capacity is specified at this current.



During the test, I took a screenshot of the result at a discharge voltage of 2.8 V: 3254 mAh or 11.19 Wh. An excellent result.


The discharge then proceeds quite quickly. At 2.5 V, I got 3330 mAh or 11.39 Wh, against a rated 3200–3350 mAh. It all matches the datasheet perfectly. Though I wasn't really in any doubt :)


At the very end, just as an experiment, I measured the capacity of the unprotected battery at a current of 6.4 A. It delivered 3101 mAh down to 2.8 V, plus another 214 mAh down to 2.5 V, for a total of 3315 mAh or 10.6 Wh. An excellent result.


During the 6.4 A test, I took several temperature measurements. The maximum was reached right at the end: 68 degrees. The photo also shows that the temperature rises rapidly toward the end of the discharge; just 4 minutes before the test ended, it was 63 degrees.
These temperatures are normal at maximum currents. Just keep in mind that Panasonic NCR18650B batteries are not high-current cells; they are designed more for maximum capacity in the 18650 form factor. Capacity and discharge current are usually inversely proportional: the higher the discharge current, the lower the battery capacity.


Since I was testing a damaged battery and its protective wrap was completely torn, it expanded a little from the heat. This can be fixed with special heat-shrink tubing. It doesn't cost much; the main thing is not to overheat the battery during the repair :)
The second photo shows that the protected batteries are noticeably longer than their "unprotected" companion.


Having completed all the tests, I can say that these are excellent batteries. They not only met their stated specifications, but also delivered very consistent results throughout the tests.
I can point out just one downside: the batteries are longer than the standard 65 mm, so make sure they will fit in your device.
Flashlights rarely cause problems, since their springs usually have plenty of travel.

That's all. I hope you found this review useful.