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Credits first - most information, and all the graphs were from http://www.mpoweruk.com/
As most of you already know, Ecigs use Lithium - ion batteries. The main reason for this is the high voltage, the way in which they discharge and their high energy density (a small battery holds a lot of power)
As you can see, after an initial steepish drop, discharge voltage remains fairly steady, up until the end, where it plummets.
Lithium batteries also hold charge well - most rechargeable batteries will self discharge in an annoyingly short period of time, typical self discharge rates for common rechargeable cells are
* Lead Acid 4% to 6% per month
* Nickel Cadmium 15% to 20% per month
* Nickel Metal Hydride 30% per month
* Lithium 2% to 3% per month
This isn't quite the whole picture however - most rechargeable batteries only have reversible self discharge - Lithium batteries actually permanently lose capacity over time! This is why ecig batteries are relatively short life items
The rate of this loss is largely temperature based.... bad news for hot titans!
The rate a battery is discharged at also affects its capacity. This is expressed as a C - rate, with 1C being a one hour discharge time, so a battery discharges in an hour at 1C, 30 mins at 2C and 2 hours at 0.5C. High discharge rates significantly damage battery life, bad news for Uber heavy users like me.
The same C rates, and their effects apply to charging (to some extent, and to keep it simple) which is why most chargers take several hours.
Lithium battery chargers are generally constant current - constant voltage, where initially a constant current is applied (resulting in an increasing battery voltage) which is then switched to constant voltage when the voltage reaches 4.2V (as overcharging lithium batteries is BAD)
Its also possible (and I haven't checked, but I imagine this is how ecig chargers work) to charge using constant current ONLY. In this case, charging stops at the end of the flat green part of the graph above. This reduces the capacity of the battery to about 80%, but simplifies the charger and usually slightly extends battery life, and of course reduces charge time :P
Most commercially sold Li batteries have a protection circuit (and that includes all ecig batteries) which does 2 things - it prevents an input voltage of more than 4.2V being applied (to prevent the likes of this happening) and to prevent it being discharged too far - if the cell voltage drops too far, the chemical reaction becomes irreversible, and the battery wont hold much if any charge.
Some of the larger Lis (such as 14500 and 18650) may, or may not be protected - if they aren't it's vitally important to use a protected charger!
As most of you already know, Ecigs use Lithium - ion batteries. The main reason for this is the high voltage, the way in which they discharge and their high energy density (a small battery holds a lot of power)
As you can see, after an initial steepish drop, discharge voltage remains fairly steady, up until the end, where it plummets.
Lithium batteries also hold charge well - most rechargeable batteries will self discharge in an annoyingly short period of time, typical self discharge rates for common rechargeable cells are
* Lead Acid 4% to 6% per month
* Nickel Cadmium 15% to 20% per month
* Nickel Metal Hydride 30% per month
* Lithium 2% to 3% per month
This isn't quite the whole picture however - most rechargeable batteries only have reversible self discharge - Lithium batteries actually permanently lose capacity over time! This is why ecig batteries are relatively short life items
The rate of this loss is largely temperature based.... bad news for hot titans!
The rate a battery is discharged at also affects its capacity. This is expressed as a C - rate, with 1C being a one hour discharge time, so a battery discharges in an hour at 1C, 30 mins at 2C and 2 hours at 0.5C. High discharge rates significantly damage battery life, bad news for Uber heavy users like me.
The same C rates, and their effects apply to charging (to some extent, and to keep it simple) which is why most chargers take several hours.
Lithium battery chargers are generally constant current - constant voltage, where initially a constant current is applied (resulting in an increasing battery voltage) which is then switched to constant voltage when the voltage reaches 4.2V (as overcharging lithium batteries is BAD)
Its also possible (and I haven't checked, but I imagine this is how ecig chargers work) to charge using constant current ONLY. In this case, charging stops at the end of the flat green part of the graph above. This reduces the capacity of the battery to about 80%, but simplifies the charger and usually slightly extends battery life, and of course reduces charge time :P
Most commercially sold Li batteries have a protection circuit (and that includes all ecig batteries) which does 2 things - it prevents an input voltage of more than 4.2V being applied (to prevent the likes of this happening) and to prevent it being discharged too far - if the cell voltage drops too far, the chemical reaction becomes irreversible, and the battery wont hold much if any charge.
Some of the larger Lis (such as 14500 and 18650) may, or may not be protected - if they aren't it's vitally important to use a protected charger!
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