How to choose 18650 batteries?

How to tell if you are fooled when facing millions fake-branded and
poor quality 18650 batteries? Here’s some useful tips to help you differ
the good from the bad.
From Capacity
Normally the 18650 lithium ion battery’s capacity won’t exceed 3100
mAh for any reason(based the 0.5 C capacity-testing standard). If you
got a 18650 battery, and labeled 5000 mAh or so, please don’t risk your
life to use it. It’s always been this case. A grade 18650 cells for
e-bikes and power tools. B grade for small assembly company of power
bank product. C grade and those below C grade for flashlight uses. While
Gpower manufactures their own A grade battery to their customers.
From Price
Some company will use LOW PRICE WITH HUGE CAPACITY to attract
customers or even distributors. The price always be something around a
0.65 USD to 1.3 USD for one single 18650 lithium ion batteries. Now you
dare to use it? No company will sell goods with a price which is much
more lower than the cost. Besides now the labor cost is increasing in
China. If there is, it could be bad ones.
From Size
There’s the risk to be deformed, leakage, explosion. Under the maniac
price war, Some companies use low price PCB protection board or EVEN
cut this part off. This kind of deeds make the market pay prices for the
explosion-able 18650 batteries. It does not come easy to tell whether
this a PCB inside. Here’s a easy way but not very reliable way. The
18650 li-ion battery’s dimension is 18mm by 65mm. 65mm is its length.
When using in a flashlight, a PCB protected 18650 would be at least
67-68mm. Yet the most reliable way is to buy it from a reliable seller.
From appearance
For the original, it has a clear color and texture. Tidy and clean
appearance. No scratch. It should be correctly labeled with Model No,
Type, Capacity, Voltage, Negative and positive indications. Metal sheets
no scratch, no blackened and greenish. If there’s inconformity then you
can tell it’s not the original.


Also look at some knowledgeable posts, like



And purchase from a reputable supplier. I use myself.

For references, is a great place full of flashlight afficianados, and they know their batteries. Numerous posts listing in-depth tests of batteries (and chargers) can be found here.

BatteryBro has some great posts on identifying counterfeit batteries, for example:


Also Mooch’s battery tests:


Copied from UKV

I’ve had good luck with Fair prices, excellent customer service (a little slow at times) and full explanation of what to look for in a battery (why they actually test batteries rather than use the manufacturer’s claim.)

Knowledge is power, and in the case of batteries…safety.

Batteries are not toys, especially Lithium-Ion.

You should own a good battery charger, and one that will read mAh capacity, then check every new battery you purchase.
A good charger, like the Opus BT-C3100, or a SkyRC will, and even has the function to refresh your rechargeable batteries as they age thru charging cycles. (among many other advanced functions)

There are only two places I fully trust to get new authentic rechargeable Lithium-Ion , especially 18650’s