This is from a madvapes.com weekly news letter. I would have posted a link however they did not archive it yet. Here it is.
We have had some questions about lithium ion batteries; their uses and limitations as well as what can cause them to fail. A lithium ion (Li-ion) battery is a rechargeable battery. While more expensive than the average rechargeable battery, they have a higher density than most others which means they can store more energy. They also can operate at higher voltages, usually around 3.7 volts. Li-ion batteries also have a lower self discharge. Rechargeable batteries will lose their charge over time even without being used. Li-ion does so at a rate of about 5-10% per month. Some rechargeable batteries can do so at a rate of up to 30% a month. Storage temperature can play a minor role in this. The higher the temperature of the storage of the battery the more charge will be lost. Storing them in a refrigerator can help to reduce this if you are not going to use them for extended lengths of time. But again this is only a small change. This is also why it is recommended that you charge your batteries when you first get them. They can have varying levels of charge based on storage time and temperature before you receive them.
Capacity, discharge rate and C rating are all related and I will talk generally about these. The big question is how long should my battery last? It is a difficult question to answer because there are so many variables involved. Capacity can be described as the amount of energy a battery can deliver in a single discharge. The discharge rate is how much load is being pulled from the battery. A higher load on the battery, such as a dual coil cartomizer, will increase the discharge rate and reduce the time a battery will last between charges. A lower more even discharge rate increases the time between charges. There is only so much energy in the battery but that energy is used more efficiently at a lower discharge rate.
The C Rating of a battery tells roughly how much continuous current a battery can give with safe operation of a battery. Each battery has a mAh rating on it. So a battery that has a 2400mAh rating on it at room temperature and with the battery at full charge with a load on it of 2.4 amps should fully discharge in 1 hour. (2.4 amps = 2400 mAh) The maximum continuous safe current is derived by multiplying the mAh rating by the C rating. If 2400mAh has a rating of C or 1C the maximum continuous safe current is 2.4 amps. Batteries also have ratings like 2C or 10C for example. This means the maximum continuous safe current would be 4.8A or 24A respectively. These are all guidelines. Variables such as temperature, cut-off voltage, age, life history of the battery, voltage drop and actual operating current will alter them.
Many of the examples given like the C rating relate to continuous operation of the batteries for items such as a light bulb in a flashlight. We are using them for electronic cigarettes which operate at much more infrequent rates, generally seconds per use when you are vaping. So operating an e-Cig and a light bulb is night and day when comparing the length of time a battery will last between charges.
The other thing that Li-ion batteries have is a protection circuit. If overheated or overcharged Li-ion batteries may suffer thermal runaway and cell rupture. In extreme cases this can lead to combustion. Deep discharge may short-circuit the cell internally, in which case recharging would be unsafe. To reduce these risks, protected batteries contain fail-safe circuitry that shuts down the battery when its voltage is outside the safe range. This could be around 2.75V on the low end and 4.2 V on the high end for a 3.7V Trustfire 18650 for example. The protection circuitry helps save the battery from dropping below a safe voltage for charging (when the voltage is under about 2.7V). Industry studies state it is generally recommended not to use a battery until it stops working and the protection circuit is activated. The reason for this is as the battery runs low it works harder and generates heat. The excess heat can harm your battery and shorten its life. Over time any Li-ion battery will stop working. But how long that takes is a factor of how much it is stressed and how deeply it is continually discharged. So running it at higher currents will decrease its life as well but not as much as continually running it until the protection circuit kicks in from deep discharge. Recharging when the battery hits 50% charge is the ideal to maximize its life.
Lithium ion batteries are also susceptible to physical damage. If you drop the batteries it is possible to break the solder points that connect the protective circuit board. This could render the battery useless. Most research is derived from tests on the batteries with continuous use. Since electronic cigarettes are more of a burst or intermittent usage the effects would be much different. If you push the button on an electronic cigarette and hold it for 30 seconds the batteries would heat up exponentially more than what an average vape lasts. Since the batteries are continually allowed to cool down in between uses the effects of usage should allow for longer life than if they were used continually.
THANKS MAPVAPES!
We have had some questions about lithium ion batteries; their uses and limitations as well as what can cause them to fail. A lithium ion (Li-ion) battery is a rechargeable battery. While more expensive than the average rechargeable battery, they have a higher density than most others which means they can store more energy. They also can operate at higher voltages, usually around 3.7 volts. Li-ion batteries also have a lower self discharge. Rechargeable batteries will lose their charge over time even without being used. Li-ion does so at a rate of about 5-10% per month. Some rechargeable batteries can do so at a rate of up to 30% a month. Storage temperature can play a minor role in this. The higher the temperature of the storage of the battery the more charge will be lost. Storing them in a refrigerator can help to reduce this if you are not going to use them for extended lengths of time. But again this is only a small change. This is also why it is recommended that you charge your batteries when you first get them. They can have varying levels of charge based on storage time and temperature before you receive them.
Capacity, discharge rate and C rating are all related and I will talk generally about these. The big question is how long should my battery last? It is a difficult question to answer because there are so many variables involved. Capacity can be described as the amount of energy a battery can deliver in a single discharge. The discharge rate is how much load is being pulled from the battery. A higher load on the battery, such as a dual coil cartomizer, will increase the discharge rate and reduce the time a battery will last between charges. A lower more even discharge rate increases the time between charges. There is only so much energy in the battery but that energy is used more efficiently at a lower discharge rate.
The C Rating of a battery tells roughly how much continuous current a battery can give with safe operation of a battery. Each battery has a mAh rating on it. So a battery that has a 2400mAh rating on it at room temperature and with the battery at full charge with a load on it of 2.4 amps should fully discharge in 1 hour. (2.4 amps = 2400 mAh) The maximum continuous safe current is derived by multiplying the mAh rating by the C rating. If 2400mAh has a rating of C or 1C the maximum continuous safe current is 2.4 amps. Batteries also have ratings like 2C or 10C for example. This means the maximum continuous safe current would be 4.8A or 24A respectively. These are all guidelines. Variables such as temperature, cut-off voltage, age, life history of the battery, voltage drop and actual operating current will alter them.
Many of the examples given like the C rating relate to continuous operation of the batteries for items such as a light bulb in a flashlight. We are using them for electronic cigarettes which operate at much more infrequent rates, generally seconds per use when you are vaping. So operating an e-Cig and a light bulb is night and day when comparing the length of time a battery will last between charges.
The other thing that Li-ion batteries have is a protection circuit. If overheated or overcharged Li-ion batteries may suffer thermal runaway and cell rupture. In extreme cases this can lead to combustion. Deep discharge may short-circuit the cell internally, in which case recharging would be unsafe. To reduce these risks, protected batteries contain fail-safe circuitry that shuts down the battery when its voltage is outside the safe range. This could be around 2.75V on the low end and 4.2 V on the high end for a 3.7V Trustfire 18650 for example. The protection circuitry helps save the battery from dropping below a safe voltage for charging (when the voltage is under about 2.7V). Industry studies state it is generally recommended not to use a battery until it stops working and the protection circuit is activated. The reason for this is as the battery runs low it works harder and generates heat. The excess heat can harm your battery and shorten its life. Over time any Li-ion battery will stop working. But how long that takes is a factor of how much it is stressed and how deeply it is continually discharged. So running it at higher currents will decrease its life as well but not as much as continually running it until the protection circuit kicks in from deep discharge. Recharging when the battery hits 50% charge is the ideal to maximize its life.
Lithium ion batteries are also susceptible to physical damage. If you drop the batteries it is possible to break the solder points that connect the protective circuit board. This could render the battery useless. Most research is derived from tests on the batteries with continuous use. Since electronic cigarettes are more of a burst or intermittent usage the effects would be much different. If you push the button on an electronic cigarette and hold it for 30 seconds the batteries would heat up exponentially more than what an average vape lasts. Since the batteries are continually allowed to cool down in between uses the effects of usage should allow for longer life than if they were used continually.
THANKS MAPVAPES!
