Comparison between 18650 battery and polymer battery

18650 battery and polymer battery are two different types of batteries. Many manufacturers will introduce these two types of batteries in different ways to highlight their respective advantages. Today we will put these two types of batteries together for comparison. I hope you can help when you choose to purchase batteries.

One: confused battery type

For readers who are not familiar with the technical principles of lithium ion battery, it is estimated that 18650 lithium battery and lithium polymer battery are the two words that are heard most. Many businesses will praise the polymer battery to the sky when promoting their products, and tread the 18650 battery to the ground, which is not too rigorous.

In fact, the principle of different types of cells are basically the same, has the positive and negative, and the electrolyte, the current mainstream single lithium batteries nominal voltage is 3.7 V, commonly the anode materials are generally cobalt acid lithium cobalt, nickel manganese acid lithium (also called ternary material), manganese acid lithium or lithium iron phosphate, etc., general for graphite anode materials, electrolyte is six lithium fluoride phosphate solution in general. Industry often use lithium batteries battery model to identify the overall size, lithium battery can be divided into several types according to different rules, such as voltage distinguish standard of high-pressure lithium batteries, lithium batteries, battery discharge ratio distinguishing them (maximum 1 c discharge), the ratio of batteries (greater than 1 c discharge), and according to the positive electrode material to distinguish pure cobalt acid lithium batteries, the ternary lithium batteries, lithium iron batteries (that is, a factory fool with independent intellectual property rights of iron battery). Lithium ion batteries are widely referred to as case packaging materials, such as the 18650 steel case packaging and aluminum case packaging of early mobile phone batteries. The mainstream is the aluminum composite film encapsulated lithium ion battery, we call the lithium polymer battery or flexible packaging battery.

It is not difficult to identify the battery used in the equipment. The 18650 battery's 18mm diameter thickness determines that its product specification thickness must be greater than 18mm and longer than 65mm. However, the low cost of 18650 determines its market share, so I hope you can choose 18650 for the low price and lithium polymer battery for the light and thin.

Two: there is no integrity of the capacity label

Do not know when to begin, a lot of people are always with greatly beautiful, feel battery capacity is taller had better, can actually have the battery of so big capacity really? As for the 18650 battery mentioned above, the capacity of a single 18650 battery of a large imported brand is 4100mAh up to now, and the capacity of a domestic battery is generally around 2600mAh. According to the total capacity generally marked at present, taking 20000mAh as an example, even if we use imported products, we need 5 parallel processes together, let alone more series and parallel processes of domestic products. Small, light and portable, it is easy to use 30000mAh, 50000mAh charging treasure, a look that is to fool people, but more gas is to use the product model to mislead consumers, such as 50000M charging treasure, buy back just know, the original 50000M is the product model, rather than the capacity of the charging treasure.

18650 battery series parallel combination consistency have high requirements for the battery itself, if a single battery internal problems, such as one of the batteries in the battery pack is low voltage, then certainly will drag down the whole battery voltage value and increase resistance, if still use the original battery by current voltage is likely to cause the battery heat explosion, lu: su flexible packaging of lithium polymer battery this is true, but relatively steel shell encapsulation 18650 li-ion battery, lithium polymer battery will not explode, but inevitably occur. So the battery capacity that the product labels is not the bigger the better.

In addition, even if it meets the capacity labeling, how much electricity can actually be provided? In order to explain this trick more directly, we take the emergency starting power supply, the next of kin - charging treasure. The capacity of the battery represents the amount of electricity that the battery itself can provide. Just like the pool, the larger the pool is, the more water is stored. The process of charging and discharging is just like the process of water storage and discharge in the pool. To charge a 3.7v battery, you won't be able to charge it at 3.7v, so you'll need a higher voltage. With 10000 mah charging treasure on the market for internal use standard is 3.7 V voltage of the battery, when the need for the same built-in 3.7 V battery charging device (currently the vast majority of batteries with lithium battery equipment are the same 3.7 voltage), must step up to 5 V (except USB interface standard voltage, USB - C), with the "clamp" rise of the battery in the transformation the conversion rate of 91% (this is a good battery), actually charging treasure output power provided by the following formula:

C=C1 * (3.7 5) * 0.91=10000mAh * 0.74 * 0.91=6734mAh

(where C represents 5V effective output capacity and C1 represents battery capacity)

That is to say, the battery charger with a capacity of 10000mAh can provide only 6700mAh in the optimal calculation of the output power of the battery charger in actual use. In the future, don't be fooled. Conscience merchants will mark the battery capacity on the product and at the same time mark the effective output capacity (the actual available capacity).

Three: the rate of battery knowledge blind spot

The discharge rate of lithium battery, we generally use the letter 'C' to represent, 1C represents the maximum discharge current of the battery is 1 times discharge,

For example, a 1000mAh 10C lithium battery means that the maximum discharge current of the battery is 10 times, and the maximum discharge current is 10 * 1000mA=10A.

Generally, we call the lithium battery with 1C discharge as the standard battery, the battery with 2c-10c discharge as the small rate battery, and the battery with more than 10C as the high rate battery.

Ratio of batteries and the traditional standard cell main difference is that the different craft, standard cells and small ratio of batteries with extremely winding process, that quick starting power supply using high rate battery its internal plate is made by the lamination process, it also provides a simple and easy to distinguish indirect method, winding technology on both sides of the battery will be slightly thick, flatness is a bit poor, and lamination process the ratio of the battery is fairly flat founder. Because the multiplier battery is designed to meet the stringent requirements of large current discharge, it USES thicker electrode plates and thicker lithium ion isolation film, with the same volume, the capacity will be slightly reduced, but relative to the safety, the sacrifice of small capacity is not enough.

With charging treasure as emergency launch power, the biggest difference is that the emergency start power is the need for instantaneous large current discharge, ignition start-up for vehicle starting motor, which need to use "ratio" battery as power, general good big ratio battery 35 c - 40 c discharge, the traditional standard cell is not qualified for this job, if the "dirty" businessman with a standard battery to provide power for emergency start power products, life doesn't grow, instantaneous large-current discharge breakdown lithium ion separation membrane, extremely easy to light several times is used, or fever burned on the spot.

Four: "optional" protection circuit

In lithium ion battery or lithium battery in use process, in order to avoid the user error caused by the operation of the battery, the battery with the decomposition of the electrolyte in the produced gas pressure rises, make its cause caused a fire and precipitation of metal lithium batteries the risk of rupture, and over discharge, degrade battery features a variety of reasons, such as in the lithium ion battery circuit and protection circuit must be used. The protection of lithium-ion rechargeable batteries must have the following four protection functions to ensure the safety and reliability of the battery. Overcharge protection prevents the battery from exceeding the limited charging voltage of the battery when charging. Overcharge of the battery can easily cause the battery to deteriorate, catch fire and break down, ensuring safety. Over-discharge protection prevents the battery from exceeding the limit voltage when discharging. Over-discharge of the battery will directly lead to the deterioration of the internal electrochemical performance of the battery, which will affect the service life of the battery in the light case and discard the battery in the heavy case. The over-current protection prevents the MOSFET from being destroyed, allowing the battery to be charged safely within the maximum charging current value it can withstand. Short circuit protection to prevent the battery from catching fire and exploding due to the direct conduction of positive and negative electrodes due to careless operation, so as to ensure the safety during use and handling. So for fake emergency start power products would be tantamount to murder the non-existing of protection circuit, especially the emergency start power by using the ratio of the battery, the protection circuit of fraud about 3-5% cost of product, but only from the appearance is don't see any protection circuit, can only by merchants conscience, so try to choose and buy the big brands.

The page contains the contents of the machine translation.