18650 Batteries

From: Battery Types, http://www.best18650battery.com/

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-For Li-ion batteries

18 - The first two digits "18" stand for the battery diameter in millimeters. In this case width of the battery is 18mm (millimeters).
65 - The third, and fourth digit stand for length in millimeters. That would be 65mm.
0 - For simplicity just forget about the last digit zero for now.

-So what is a 16340 battery ?

16mm - diameter 34mm – length

Besides size and capacity, you may notice the 3 letter codes on most Li batteries like ICR, IMR, INR, NCR, etc. printed on the battery like the Samsung ICR18650-26F, INR18650-30Q, Panasonic NCR18650B, etc. These are various types of Li-ion batteries . The 3 letter codes are manufacturer codes, and most but not all, use this as a standard way to refer to the different types of cells.

“I_R”

The first Letter "I" just means that the cell is a Li-ion rechargeable.
Second letter refers to the cathode material.
The last letter "R" just means the cell is round.

ICR = Li-ion Rechargeable, the "C" = Cobalt. IMR = the "M" stands for Manganese, or "Mn". INR = the “N” stands for Nickel. IFR = the "F" stands for the element "Fe" which is Iron.

INR seems to have rather similar proterties to IMR i.e. low internal resistance and delivery high current without causing the battery from getting too hot. It is also classified as a safer chemistry so it's another ideal high drain battery.

-What about Panasonic NCR18650B ?

The name NCR18650B is just Panasonic’s part number and it’s also a Lithium Cobalt battery, like an ICR cell. Panasonic does put some additional safety features that make it safest of any ICR cell.

The NCR18650B is available with and without protection. Again for protected cell, it may be offered as a rewrapped under different brand or same brand but the dimension will be longer and wider, so it may not suit some devices.

Capacity or mAh (milliampere hour) Rating - an approximation for how long a battery charge should last on a full charge. This is the battery capacity and is used to describe a battery's "fuel tank", as in general a battery with higher mAh ratings will last longer assuming that it's subjected to same usage patterns.

To estimate how long a battery last, divide the capacity of battery by the current consumed by device. For example, the battery is 3400mAh and a cree torch consumed 2.4A (2400mA), it will last 1.42 hours approx. If you use a 2600mAh, it last you only 1.08 hours only.

The "best battery" is not always the one with the largest mAh rating. In most applications a higher current rating (C-rating) determines the better battery.

The C rating is the maximum safe continuous discharge rate of a battery. If you see 10C on your battery, it means it can be discharged at 10 times that cell’s capacity. Capacity refers to the milliamp-hour rating of the battery, which will be listed as a number followed by mAh (2000mAh, for example). Here's the easy way to find your battery's discharge rate; just multiply the number from the C rating by the cell's capacity. Keep in mind that 1000 milliamps equals one amp.
Here's an example, using an 3.7V 2000mAh 10C

3.7 volt 2000mAh -10C 2000 milliamps = 2 amps 2 Amps x 10 = 20 amps continuous discharge

This means that you can safely draw up to 20 amps continuously from that 3.7V 2000mAh 10C without doing damage to your battery.

-Example: Samsung ICR18650 26-F 2600mAh 2C

It means the max. continuous discharge current is 5.2A (2.6x2). Now you know why this battery price is so low, because of low C-ratings and also not really a high capacity (mAh) battery.