Interest in, and usage of, Lithium (Li) Iron (Fe) Phosphate (PO4) cells (LiFePO4) for vaping --- primarily with mechanical devices --- while low, seems to be growing of late. Perhaps this thread can provide a place for discussing general information, resources, and experiences with respect to vaping with LiFePO4 cells.
First things first: LifePO4 chemistry cells are not simple drop in replacement cells for the more typical cells we use in vaping, and are not really suitable for most regulated or protected mods. LiFePO4 cells have a nominal voltage of 3.2v/3.3v and a maximum charge of 3.6v, whereas our typical lithium cells have a nominal voltage of 3.6v/3.7v and a maximum charge of 4.2v.
Under load, a LiFePO4 cell will put out a voltage around its nominal voltage or a little lower, and thus are not suitable for most regulated mods, or unregulated with protections mods for the simple fact that it runs at a voltage that is at or near the low voltage cutoff of most such mods (on DNA mods, one can (apparently) use the Escribe software to set a lower voltage cutoff point). Additionally, regulated mods don't have proper charging circuitry for such cells, so attempting to use the on-board charging with such a cell would very likely lead to battery failure from overcharging (and perhaps mod damage and personal injury).
Also note: you will need a charger with an explicit LiFePO4 charging mode/setting. I currently use the Xtar VP2, but there are others.
So, what are some benefits of using them in a mechanical mod?
Number one is safety --- the LiFePO4 chemistry is inherently safer than other lithium cell chemistries. Cells with this chemistry are much more resistant to thermal runaway and violent flaming failure (but not immune to such failure). Now, I don't personally think of our regular lithium batteries as unsafe or dangerous in and of themselves --- millions are in use in the vaping community everyday and the small number of mishaps are almost always due to user error, carelessness, or relatively rare mod malfunctions. I examine my cells everytime I remove them from a mod to put on a charger, and everytime I put a fresh cell into a mod, and I rewrap them at the slightest indication of a problem with the wrap, and I will continue to do so with LiFePO4 cells. Still, it's nice to have a safer chemistry cell that also has the next benefit.
Number two is the flat discharge curve --- LiFePO4 cells maintain a much flatter discharge voltage across most of their capacity than do other cell chemistries. This means we can get something more like a constant voltage vape without voltage regulation circuitry. I am getting around a 3 watt drop over about 85% of the capacity of a 2600mah Vapcell IFR26650.
Number three: longer life --- LiFePO4 cells also have longer shelf life, handle sitting at full charge better, and have longer cycle life than other lithium cells.
The big trade-off? Energy density. Simply put, size for size, LiFePO4 cells have lower total energy than our more familiar lithium cells. So we are looking at 1100mah for a high drain 18650 cell, and 2600mah for a high drain 26650 cell. The good news is, you can use a lot of that capacity while getting a fairly stable vape (due to the relatively flat discharge curve).
What am I using?
I began experimenting with LiFePO4 using Vapcell IFR26650 cells in a Chi You Megan mechanical tube mod, and eventually found and purchased a 26650 squonk mod (my preferred mode of vaping). As mentioned above, I am using an Xtar VP2 charger which has a physical switch/setting for LiFePO4 charging. The Vapcell IFR26650 cells are 2600mah and rated at 55-amps continuous discharge, but the only third party testing I've seen tested up to 30 amps, which the cells handled fine.
Test of Vapcell IFR26650 2600mAh (Red)
I am an MTL vaper, in the mid-teens to twenty watt neighborhood. Using a 0.5 ohm coil with these cells I can get about 2250mah of consistent vaping falling just 3 watts (about 21 watts to 18 watts).
More recently I ordered some 18650 LiFePO4 cells (both A123 Systems and Lithium Werks --- Lithium Werks acquired the A123 Systems industrial business in 2018). These cells are just 1100mah and rated at 30-amps continuous discharge:
A123 Systems 18650 cell review:
Test of A123 18650 1100mAh (Yellow)
!8650batterystore has the LW cells, and shows a discharge graph as well:
Lithium Werks 18650 1100mAh 30A LiFePO4 Battery - 18650 Battery Store
I should get the LW cells on Friday, the A123 cells perhaps next week. From the info and discharge graphs I've seen thus far, I expect a slightly lower comparative performance relative to the IFR26650 cells, perhaps giving (again, with a 0.5ohm coil) about 900mah of vaping, falling from about 20 watts to 17 watts. It doesn't sound like much capacity, but with my vaping style, 900mah can see me through much of a day. And, since I always have multiple vapes going, I don't usually use anywhere near 900mah on any single device in a day.
For vapers wanting more power, the IFR26650 look to be the better choice (if you don't mind the size of a 26650 mod), and of course, a series mech is always an option.
I know a few others here are using LiFePO4 cells in mechanical mods, so please join in and share your experience: what cells, what mods, what coils/resistance, and what charger(s) are you using.
I will update when my A123 and LW 18650 cells arrive and I have a chance to try them out.
First things first: LifePO4 chemistry cells are not simple drop in replacement cells for the more typical cells we use in vaping, and are not really suitable for most regulated or protected mods. LiFePO4 cells have a nominal voltage of 3.2v/3.3v and a maximum charge of 3.6v, whereas our typical lithium cells have a nominal voltage of 3.6v/3.7v and a maximum charge of 4.2v.
Under load, a LiFePO4 cell will put out a voltage around its nominal voltage or a little lower, and thus are not suitable for most regulated mods, or unregulated with protections mods for the simple fact that it runs at a voltage that is at or near the low voltage cutoff of most such mods (on DNA mods, one can (apparently) use the Escribe software to set a lower voltage cutoff point). Additionally, regulated mods don't have proper charging circuitry for such cells, so attempting to use the on-board charging with such a cell would very likely lead to battery failure from overcharging (and perhaps mod damage and personal injury).
Also note: you will need a charger with an explicit LiFePO4 charging mode/setting. I currently use the Xtar VP2, but there are others.
So, what are some benefits of using them in a mechanical mod?
Number one is safety --- the LiFePO4 chemistry is inherently safer than other lithium cell chemistries. Cells with this chemistry are much more resistant to thermal runaway and violent flaming failure (but not immune to such failure). Now, I don't personally think of our regular lithium batteries as unsafe or dangerous in and of themselves --- millions are in use in the vaping community everyday and the small number of mishaps are almost always due to user error, carelessness, or relatively rare mod malfunctions. I examine my cells everytime I remove them from a mod to put on a charger, and everytime I put a fresh cell into a mod, and I rewrap them at the slightest indication of a problem with the wrap, and I will continue to do so with LiFePO4 cells. Still, it's nice to have a safer chemistry cell that also has the next benefit.
Number two is the flat discharge curve --- LiFePO4 cells maintain a much flatter discharge voltage across most of their capacity than do other cell chemistries. This means we can get something more like a constant voltage vape without voltage regulation circuitry. I am getting around a 3 watt drop over about 85% of the capacity of a 2600mah Vapcell IFR26650.
Number three: longer life --- LiFePO4 cells also have longer shelf life, handle sitting at full charge better, and have longer cycle life than other lithium cells.
The big trade-off? Energy density. Simply put, size for size, LiFePO4 cells have lower total energy than our more familiar lithium cells. So we are looking at 1100mah for a high drain 18650 cell, and 2600mah for a high drain 26650 cell. The good news is, you can use a lot of that capacity while getting a fairly stable vape (due to the relatively flat discharge curve).
What am I using?
I began experimenting with LiFePO4 using Vapcell IFR26650 cells in a Chi You Megan mechanical tube mod, and eventually found and purchased a 26650 squonk mod (my preferred mode of vaping). As mentioned above, I am using an Xtar VP2 charger which has a physical switch/setting for LiFePO4 charging. The Vapcell IFR26650 cells are 2600mah and rated at 55-amps continuous discharge, but the only third party testing I've seen tested up to 30 amps, which the cells handled fine.
Test of Vapcell IFR26650 2600mAh (Red)
I am an MTL vaper, in the mid-teens to twenty watt neighborhood. Using a 0.5 ohm coil with these cells I can get about 2250mah of consistent vaping falling just 3 watts (about 21 watts to 18 watts).
More recently I ordered some 18650 LiFePO4 cells (both A123 Systems and Lithium Werks --- Lithium Werks acquired the A123 Systems industrial business in 2018). These cells are just 1100mah and rated at 30-amps continuous discharge:
A123 Systems 18650 cell review:
Test of A123 18650 1100mAh (Yellow)
!8650batterystore has the LW cells, and shows a discharge graph as well:
Lithium Werks 18650 1100mAh 30A LiFePO4 Battery - 18650 Battery Store
I should get the LW cells on Friday, the A123 cells perhaps next week. From the info and discharge graphs I've seen thus far, I expect a slightly lower comparative performance relative to the IFR26650 cells, perhaps giving (again, with a 0.5ohm coil) about 900mah of vaping, falling from about 20 watts to 17 watts. It doesn't sound like much capacity, but with my vaping style, 900mah can see me through much of a day. And, since I always have multiple vapes going, I don't usually use anywhere near 900mah on any single device in a day.
For vapers wanting more power, the IFR26650 look to be the better choice (if you don't mind the size of a 26650 mod), and of course, a series mech is always an option.
I know a few others here are using LiFePO4 cells in mechanical mods, so please join in and share your experience: what cells, what mods, what coils/resistance, and what charger(s) are you using.
I will update when my A123 and LW 18650 cells arrive and I have a chance to try them out.
