All size (form factor) 18650 batteries have their pros and cons. Therefore, it is difficult to talk about which 18650 batteries are better. Rather, it is a matter of personal preferences and requirements that you make to the battery. Technical specifications and features of the battery depend on the type of chemistry used (electrolyte).
Protected and unprotected lithium-ion batteries
To begin, consider the difference between protected and unprotected 18650 batteries. Which of the two types is best will become clear after analyzing these terms. Protected batteries are batteries with a small circuit board (charge controller) embedded in the case, which has three most necessary functions: protection against short circuit, protection against deep discharge, and exceeding the permissible amperage when charging. Along with protected batteries, there are also unprotected batteries without an internal board. You have to be very careful with such ones, especially forcing them to work with very low resistance.
Depending on the chemical composition of an unprotected battery, it can either deteriorate forever or just explode. You can find out if the battery is protected by reading the small inscriptions on its case. Short circuit in translation into English will be Short-circuit, protection - Protection. If you meet these two words on the same line, you can be sure of the protection. Also, individual Protection or Protected words will say the same thing. Unfortunately, not all batteries write about the presence of a small savior in it. Alternatively, you can search for battery information from sellers or online. If you put safety at the forefront when choosing a battery, the answer to the question of which battery is better than the 18650 becomes obvious.
Mechanical protection of lithium-ion batteries
In addition to electronic internal battery protection, there is also a mechanical protection system without using a board. The meaning of such protection is reduced to mechanical breaking of the circuit (operation of a mechanical switch) inside the battery as a result of exceeding a certain threshold of internal pressure, which, in fact, leads to an explosion. This de-energizes the battery. If the pressure still continues to increase, then a special valve is automatically opened, which extracts the electrolyte out. The mechanical switch itself is quite widespread as an additional safety measure in many batteries, built-in with or without a charge controller (board). At the same time, the presence of mechanical protection may not be mentioned at all anywhere, either on the case or in the description of the technical characteristics in the store. In this case, you just need to understand that batteries with an unstable chemical composition a good manufacturer will never leave without protection. Even if officially such a power source is considered unprotected, in any case there will be at least some kind of mechanics in it.
Li-ion battery capacity
Battery capacity is expressed in milliamperes per hour (mAh or mA * h) and also helps determine which 18650 battery is best for use on the device you need. The higher this value, the longer the battery will last until it is fully discharged. Milliampere per hour is the derivative of “ampere per hour” (1 Ah = 1000 mAh), used for small batteries. Without delving into physics, this value characterizes the potential current strength of the battery, which it must give out within one hour in order to completely discharge. Of course, he may not give out such a strong current, but by this value one can easily judge its capacity. Using simple calculations, you can find out what current the battery will produce during several hours of operation, based on equality - the number of amperes in one hour. The larger the ampere value, the longer the battery can last with the same power.
Current efficiency of lithium-ion batteries
Current output is another parameter that characterizes a battery. On the battery case, the current collector is marked by current - ampere (A). The more amperes there are, the stronger the battery will “fry”. High ampere batteries are considered High drain. It is the number of amperes that determines which high-current 18650 battery is better. However, such batteries have a relatively small capacity. The lower the resistance with which the battery should work, the more current it will have to give. And the limit of this return depends on the described value.
The battery capacity determines the current strength in the context of time, and the current output shows this limit. Based on these two parameters, you can calculate the maximum battery runtime with the maximum possible force for it. It is important to understand that if the current required for a particular device is greater than the maximum current output of the battery with which this device works, then for the battery it will be an overload. The working life of the battery during continuous operation under heavy load is greatly reduced.
Ohm's law as a method to find out which 18650 batteries are better by technical characteristics
Knowing the rated voltage of the power source and the resistance of the device, it is possible to calculate the necessary current efficiency using Ohm's law:
I = U / R, where I is the current in amperes (A), U is the voltage in volts (V), R is the resistance in ohms (Ohm).
That is, you need to divide the battery voltage by the resistance of the final device. Using the formula, you can protect the battery from possible overload in work, and certainly from a short circuit. Ohm meters are used to measure resistance. The ability to perform such simple calculations will help determine which 18650 battery is best suited for use on a particular device.
All 18650 form factor batteries have a nominal voltage of 3.7 volts. But this value in most cases is variable and depends on the level of battery discharge. The more it is discharged, the less volt it produces.
Types of Li-ion batteries
Which 18650 battery to choose and which one is better depends on the specific situation. Knowing the features of various types of chemistry will help to understand this issue. Below are the most popular types of chemistry for 18650 batteries:
- Lithium cobalt - ICR, NCR, LiCoO 2 (Lithium Cobalt Oxide).
- Lithium Manganese - IMR, INR, NMC, LiMnO 2 , LiMn 2 O 4 , LiNiMnCoO 2 (Lithium Manganese Oxide).
- Lithium iron phosphate (ferrophosphate) - LFP, IFR, LiFePO 4 (Lithium Iron Phosphate).
The listed types of batteries are varieties of lithium-ion batteries, that is, made by lithium-ion technology.
The information below with descriptions of the types of chemistry will help determine which 18650 lithium-ion battery is better.
Aging, storage and operating temperature range of lithium-ion batteries
All lithium-ion power sources are aging. It does not matter if they are used at all. It is believed that after several years from the date of production in any scenario, they can be safely thrown away. Each year, the battery loses about 10% of the nominal capacity, so it is recommended that you know the date of manufacture before buying. Along with aging, lithium batteries have another small drawback - they can not be stored for a long time in a discharged state, this can ruin them. The batteries are also affected by the ambient temperature. For lithium-ion cells, the operating temperature range is relatively low - from -20 degrees to +20 degrees Celsius. This means that using or charging them under conditions close to the indicated boundaries will adversely affect the electrolyte.
Lithium cobalt batteries
Lithium-cobalt batteries are characterized by the highest rates in capacity. Lithium-cobalt chemistry is very unstable, so use it carefully. The possibility of fast charging should not be allowed when using the accelerated or delta V charge method. With this charge, a more stable battery can fully charge in one hour. It is dangerous to charge lithium-cobalt in this way. Also, you cannot use a lithium-cobalt battery with such a load that it can discharge in less than 30 minutes. For batteries with this chemistry without protection, both will lead to ignition of the electrolyte.
Chemistry based on lithium-cobalt technology has found great popularity among 18650 batteries for electronic cigarettes. What is the best battery manufacturer in this category to choose, it is recommended to look in the reviews. Due to some instability, these batteries must be selected with care.
The threshold value for the charge of a lithium-cobalt battery is the limit of 4.2 volts. A surge in battery voltage above this limit will mean overcharging, which is highly discouraged. Using too powerful chargers adversely affects lithium-cobalt chemistry. This spoils the battery and at the same time increases the risk of ignition and explosion of electrolyte. It is best to use advanced chargers with the ability to adjust the supplied current and apply different settings for charging. The best charging method here is the CC / CV algorithm - constant current, constant voltage (Constant current / constant voltage).
Cobalt batteries are badly affected not only by overcharging, but also by overdischarge. The peak threshold for discharge is the 3-volt boundary. If you continue to work on cobalt after reaching such a battery voltage, it will spoil it, increasing the risk of ignition. Ideally, you need to stop working on cobalt after 3.5 volts. Attitude to lithium-cobalt chemistry should be the most careful. Overcharge, overdischarge, excessively low ohm on discharge, physical damage will contribute to the deterioration of chemistry, which will ultimately lead to an explosion. In cases with a very high charge current and a very low resistance, it can occur immediately. Nickel-cobalt chemistry is very toxic. When ignited, it emits very harmful gases, which, if inhaled, can be fatal.
Lithium manganese batteries
Lithium-manganese batteries are the most popular, primarily due to the stability of their chemistry with almost the same properties as cobalt batteries. Therefore, a charge controller is not placed on many manganese batteries, and at the same time, manufacturers proudly hang a “safe” flag on them.
Manganese batteries are capable of long and quiet operation in the load (with a very low ohm). This, of course, is not good in any case, but unlike cobalt elements, manganese will last much longer in this case. Manganese elements have a good balance of capacity and strength, but lose cobalt in capacity. Precautions when charging IMR batteries are almost the same as cobalt ones. The maximum border is 4.2 volts. The use of high currents on the charge will not blow up the electrolyte, but it will greatly spoil it. And this, of course, depends on the strength of the supplied current. The stronger it is, the faster it will charge, but the worse it will be for chemistry. The recommended charging method is CC / CV. Another plus of manganese elements is that they are able to withstand a deep discharge of 2.5 volts. Anyway, you should not often bring the manganese battery to this state.
This type of electrolyte is also characterized by the absence of an explosive effect. This is due to the use of graphite as a material for the anode. In case of critical violation of operating conditions (very low resistance or very high current to charge), gas will be released even on the battery without protection, but ignition or explosion will not occur.
In general, due to its averaged performance, lithium-manganese 18650 batteries are better in performance. What kind of batteries in this category to choose should be looked at in reviews separately for each of the manufacturers.
Lithium iron phosphate batteries
Lithium iron phosphate (ferrophosphate) are the safest of the family of lithium-ion batteries. This is their main difference. The chemistry stability of LFP batteries is even better than that of manganese. This is due to the use of an iron phosphate cathode, which has excellent heat resistance and no toxicity. Almost all iron-phosphate batteries are not equipped with a charge controller, and to bring them to an explosion or fire without physical damage, you need to try hard. They tolerate various abuses at work, for example, very low resistance.
Ferrophosphate cells have the highest life (2000 charge-discharge cycles) among lithium-ion ones. Of the minuses - low capacity, about 50% lower than that of cobalt, and about 15% lower than that of manganese batteries. Another feature of these batteries is the voltage stability during use, which fluctuates near the border of 3.2 volts until discharge. This property gives ferrophosphate batteries more advantages for using them in series connection (if the batteries are assembled in a circuit, that is, in a rechargeable battery). Iron-phosphate batteries have a lower current output than their counterparts in chemistry, but high-current batteries can also be found among them. Iron-phosphate batteries age a little slower than other lithium-ion batteries, but, like the ones described above, they cannot be stored discharged.
In search of information about which 18650 battery is better for a flashlight or a radio-controlled model, it is recommended to opt for batteries with this chemistry. In view of the above properties, they are excellent for use in batteries of these devices.
The chemistry of these power sources allows you to safely charge them using the accelerated method. Ferrophosphate batteries are very rechargeable. As for the discharge, its maximum permissible boundary is 2 volts. Toward the end of the operation, the steady-state battery voltage will drop sharply. Frequent discharge below this limit will quickly ruin the battery.
In conclusion
This is a description of the battery markings, technical characteristics of the 18650, which are the best of them, and different types of chemistry we will end. We hope that this information will help determine which battery is suitable for a particular device. The recommendations and characteristics given here are given in a very concise form. Entire forums, websites, and even books are dedicated to batteries. The most complete information about them cannot be put in one article. We are no longer talking about the fact that for their study it is necessary to know many special terms and electrochemistry in general.