How to choose 18650 lithium batteries (brand, capacity, continuous discharge current)
Choose the most suitable
18650 lithium battery for our electrical equipment, such as the appropriate brand, voltage, capacity, continuous discharge rate, battery life, etc. The most important thing is to choose a battery with high safety. Below, we will provide a detailed introduction one by one:
1. Battery brand
Regarding brands, internationally renowned brands such as Sanyo, Samsung, SONY, LG, etc. are currently more reliable.
Sanyo and LG focus on conventional applications, mainly in strong light flashlights, power banks, laptop batteries, etc.
SONY specializes in high power and current. Taking VTC4 as an example, the discharge current can reach 30A, and it can easily handle electronic cigarettes, toy airplane models, etc.
2. Nominal capacity
The nominal capacity of an 18650 battery is related to its endurance, measured in "mAh". The higher the capacity, the stronger the endurance. For example, a 2800mAh battery can discharge continuously for 2 hours with a current of 1.4A.
At present, the phenomenon of false labeling of battery capacity is very serious. The vast majority of domestic 18650 lithium batteries with a capacity exceeding 3000 are falsely labeled. Currently, only Panasonic has the highest capacity and can be purchased with 3400mAH. The capacity of domestic batteries is generally between 2200-2800mAh. At present, in addition to buying battery cells from large manufacturers to ensure that there is no or very little virtual labeling of capacity, ordinary users only use discharge meters to test capacity.
In addition to false labeling, be careful not to purchase disassembled batteries when purchasing. Disassembled batteries are usually removed from discarded battery packs and are close to being scrapped, so there is no need to waste money~
3. Continuous discharge current (CDR)
The continuous discharge capacity is represented by the C number, and the continuous discharge current=the continuous discharge capacity C number multiplied by the capacity.
For example, if the capacity of an 18650 battery is 2800mAh and its continuous discharge capacity is 0.5C, then the continuous discharge current is 1.4A. If the discharge exceeds 1.4A for a long time, it will seriously affect the battery life and may pose risks such as overheating, combustion, and explosion. The parameter of continuous discharge capability is usually written on the battery introduction page, so be sure to pay attention to it. Some parameters directly state the continuous and maximum continuous discharge current.
4. Internal resistance
Internal resistance is the resistance of the battery itself. The smaller the internal resistance, the less it consumes and the stronger its discharge capacity. This parameter is usually written on the battery introduction page. When purchasing, it is also important to pay attention and try not to buy batteries with a resistance of more than 100m Ω.
When using multiple 18650 batteries in series, it is necessary to buy batteries of the same brand and model, otherwise batteries with high internal resistance and low capacity will become a weakness.
5. Temperature
Temperature is a major factor affecting the lifespan of 18650 lithium batteries. The higher the temperature, the faster the aging of lithium batteries will occur, and the greater the damage to the internal structure of lithium batteries.
6. Sharp pointed and flat headed
There are two types of 18650 lithium batteries: flat head and pointed head. The positive electrode on the left side with a protrusion is pointed head, while the positive electrode on the right side without a protrusion is flat head.
In general, I recommend purchasing pointed batteries to ensure compatibility with a wider range of devices and applications. Usually, the positive and negative poles of flashlights are designed with springs, which can be extended and retracted. Both pointed and flat batteries can be used. But if a flat head battery is to be used in series, the positive pole of the flat head cannot contact the negative pole of another battery.
7. With and without protective board
Sharp 18650 with protective plate, flat
18650 without protective plate.
The 18650 lithium battery with a protective plate is several millimeters higher and slightly more expensive than the one without a protective plate, but it has higher safety and stronger universality. The 18650 lithium battery with a protective plate can prevent the battery from overdischarging, which can cause the battery to heat up and even pose risks such as combustion and explosion.
