Viewing blog entries in category: General Battery Stuff
It's widely believed that the LiPo battery packs used in DNA200/250 and custom box mods need to be charged/discharged several times before they reach their peak performance.
Is this true?
To find out I took three new 3S packs and balanced charged them at 5A on an iCharger106B+ to 12.60V followed by a discharge to 9.0V at 20A constant-current. I did this a total of five times for each pack with a 60 second rest between each step. A lot of effort was made to ensure that the pack temperatures were consistent from cycle to cycle.
Here are the three discharge graphs:
As you can see there was no increase in the capacity of the pack or an increase in its voltage while being discharged (which would indicate a decrease in its internal resistance).
For two of the three packs I measured the internal resistance before and after the tests were done:
Turnigy 25C-35C 2200mAh before = 18.3 mOhms
Turnigy 25C-35C 2200mAh after = 18.5 mOhms
MaxAmps 100C 2250mAh before = 21.9 mOhms
MaxAmps 100C 2250mAh after = 22.8 mOhms
The break-in cycles didn't lower the internal resistance of the packs. In fact, they did exactly what any use of the pack does...ages the pack and increases its internal resistance.
The break-in cycling did not improve the performance of any of the three packs. It only wasted five of the limited number of cycles available before the packs would need to be replaced.
I also did five break-in cycles for each of the ten 1800mAh 3S LiPo packs I recently tested. Those break in cycles were done at some pack assembler's typical recommended levels, 1C charge and 2C-3C discharge. There was no increase in performance between cycle 1 and cycle 5 for any of the packs.
Will this be the case for every LiPo? I don't know.
There might be some LiPo's that were not fully formed (initialized) at the factory in order to save money. Their performance would increase during the first few cycles. There also might be some that were stored for a long time before being used. This can cause the thickening of an important chemical divider (the SEI layer) between certain parts of the battery, increasing its internal resistance. Cycling the battery can reduce its thickness and restore some performance.
I know that many in the R/C community feel strongly that this cycling is needed but the tests described above and my recent testing of ten different 1800mAh 3S LiPo packs showed no increase in performance after being cycled a few times.
I have an idea why some might feel they are seeing an improvement in performance though.
LiPo cells, which use lithium-cobalt chemistry, show a very small change in voltage for a big change in capacity during most of the discharge compared to other Li-Ion chemistries. This "flat discharge curve" is one of the big benefits of using LiPo's.
But this flat discharge curve also means that just a small change in the voltage of the battery can result in a big change in the capacity the battery delivers to cutoff voltages above 3.2V or so. If the pack is warm its internal resistance drops and the voltage the pack runs at is higher. This allows the pack to run for a lot longer before dropping to the cutoff voltage.
Since the outer wraps of a LiPo pack are very effective heat insulators the internal temperature of a LiPo pack can be a lot higher than the external temperature. It can seem to be only a bit above room temperature but actually be much warmer. Unless the pack is allowed to sit for at least an hour after charging, two hours or longer for larger packs, the internal resistance could be lower than when the pack was first used in the tests.
This would cause the packs to run at a higher voltage, making it seem that its performance had improved with cycling. But the improved performance was really only due to the pack being warm.
I am not saying that everyone who cycles their packs and says they see an improvement is wrong!
I am not saying that no LiPo packs respond to break-in cycling!
I am merely saying that in my testing of thirteen different packs I see no sign of break-in cycling having any effect on performance. It shouldn't though. Properly formed packs, not stored for months and months, should not need any sort of break-in to reach their best performance levels.
I'd be interested in hearing your experiences regarding breaking in LiPo packs, especially if you took measures to make sure internal pack temperatures were consistent for each cycle.
It's time to put this myth to rest. Using rice to help dry batteries or a mod that got wet doesn't help at all. In fact, it slows down evaporation of any water that is inside.
I set up a 24 hour test using paper towel sheets with enough water added to bring their weight to 18 gms. I then put these wet folded paper towels in four places; a slightly ventilated box in rice, a slightly ventilated box 3 feet in front of a fan on low, a bare folded paper towel in still air, and a bare folded paper towel 3 feet in front of a fan on low. The complete results are in the table but two are presented here...
- Amount of water that evaporated from the box in the rice after 24 hours = 2 gms
- Amount of water that evaporated from the box in front of the fan after 24 hours = 10 gms
Since the device that is wet is buried in rice, with no air movement, the humidity level quicky rises up to 100% next to any water that is present inside the device. This significantly slows down any evaporation that could take place.
Adding air movement blows away the layer of very humid air above any water, allowing the water to evaporate much faster.
Some of you might have tried using rice and found that you could turn on your mod a day or two later and it worked. But did you open up your mod to see if the water had actually evaporated? How can we know that the rice did anything?
Bottom Line: If you have a mod that got wet, do not turn it on. Remove the batteries (if possible), shake out any water you can, and then place it in front of a fan. Rotate it every couple of hours to try to get any blowing air into any seams or ventilation holes. It should be pretty dry internally in 24 hours.
Please don't bury it in rice!
 I'm sure there will be those who feel this test was invalid for one reason or another. It's backed up by every good test like this I found online but I strongly encourage anyone who feels I erred to do their own tests. I would love to see the results!
 For those who are concerned that the paper towels "lock in" the water, keeping it from evaporating:
Pictures of the setups:
PBusardo was kind enough to offer me a page on his web site and I jumped at the chance. The first article is up. Thank you for this opportunity Phil!
It's tempting to use very high capacity batteries, over 3000mAh, to try to get more vaping time before needing to recharge. But there aren't any 18650 batteries with a capacity over 3000mAh that have a rating above 10A!
Batteries like the Panasonic 3200mAh NCR18650B look like a great way to get more vaping time but they're only rated at 4.9A. And the Efest, Imren, and other Chinese-company high-capacity batteries are just rewraps of 10A Panasonic and LG batteries.
If you vape at under 20W (per battery) or so then you can use the 3200mAh Panasonic NCR18650B.
If you vape at under 35W (per battery) or so then you can use the over-3000mAh Efest's, Imren's, etc. But Panasonic/Sanyo NCR18650GA, LG MJ1, and LG MH1 batteries are less expensive and possibly a higher grade.
Can you vape at higher power levels with these 4.9A and 10A batteries? Of course! The batteries won't explode and your face won't melt off if you do.
But the voltage sag is so severe that at over about 5A-7A you can actually get more vaping time from the 3000mAh LG HG2 and Samsung 30Q. This is because their internal resistance is lower than the over-3000mAh batteries. This allows them to run more efficiently, with less voltage sag, and that means they run for longer before your mod says low/weak battery.
So, know your batteries and vape safe.
If you want to start going beyond what www.batteryuniversity.com covers here are a few of the more interesting papers I've read on Li-Ion batteries. They are quite technical though!
Thermal runaway caused fire and explosion of lithium ion battery:
Thermal runaway in Li-Ion — getting the missing data:
http://www.helgroup.com/articles/pdf/b426f8c49b436d84/Thermal Runaway in Li-ion Article Best Tech Magazine.pdf
Theory of SEI Formation in Rechargeable Batteries:
Advanced Technology Development Program for Lithium-Ion Batteries, Thermal Abuse Performance of 18650 Li-Ion Cells:
Are Lithium Ion Cells Intrinsically Safe?:
Understanding Lithium-Ion Technology:
Mechanism of intercalation and deintercalation of lithium ions in graphene nanosheets:
Mechanism of intercalation and deintercalation of lithium ions in graphene nanosheets | SpringerLink
In-operando high-speed tomography of lithium-ion batteries during thermal runaway:
Some thermal runaway and Li-Ion abuse papers:
http://www.helgroup.com/articles/pdf/b426f8c49b436d84/Thermal Runaway in Li-ion Article Best Tech Magazine.pdf
http://www.battcon.com/PapersFinal2015/17 Ponchaut Paper 2015.pdf
Aging Mechanisms in Li-ion Batteries:
Degradation Mechanisms and Lifetime Prediction for Lithium- Ion Batteries – A Control Perspective:
You are responsible for your own safety!
These batteries are designed, manufactured, and sold only for use in a battery pack with the proper protection circuitry and battery management system. They were not designed for vaping (electronic cigarette) use or for use without protection circuitry. Use of these batteries is AT YOUR OWN RISK!
Misusing or mishandling lithium-ion batteries can pose a SERIOUS RISK of personal injury or property damage.
- Only buy batteries from a known, trusted vendor of genuine batteries.
- Never use a battery, charger, or device that is not in perfect working order.
- The plastic battery wrap and top insulating ring must always be kept in perfect condition to prevent short-circuiting of the battery which can result in the battery bursting.
- Never exceed the battery's continuous discharge rating (CDR) or charge rating.
- I am not responsible for any damage or injury sustained by anyone using this information to select a battery.
It does not mean I think your batteries are bad if you use ones not on this list!
These are merely my personal recommendations to help reduce the number of different batteries to choose from.
Note: The non-Samsung/Sony/LG/Panasonic/Sanyo batteries can change what is used under the wrap at any time.
There are several things you can do to help your Li-Ion batteries last as long as possible before needing to replace them. Some are easy, some are quite inconvenient. Some have a big effect, some very little. But doing any of them can help slow down the aging and degradation of your batteries.
- Don't overheat them. High temperatures are the biggest cause of battery damage and reduced battery life. Anything over about 45°C/113°F, what most would call warm, and your batteries start aging faster. The more time they spend being warm or hot, and the hotter they get, the more damage you're causing.
- Don't use them when they're very cold, below -20°C/-4°F. The chemical reactions in a battery are a lot less efficient at low temperatures leading to poor performance. The sudden heating of the battery if used when cold can cause localized internal heating, possibly damaging the battery.
- After using your battery, let it cool to room temperature before charging it.
- Don't overdischarge them. Our batteries are rated down to 2.5V or lower but you can extend their life by staying above 2.8V-3.0V***. Going below 2.0V or so leads to metal being plated inside different parts of the battery, eventually causing an internal short circuit and possible bursting of the battery.
- If you accidentally overdischarge your battery below 2.0V immediately recharge it at the slowest rate your charger supports. Once the battery rises up over 3.0V or so you can switch to your normal charge rate.
- If battery has been at 2.0V for a while then it's probably damaged. It's not worth trying to use the "recovery" mode of your charger (if it has it) because the damage can lead to an internal short circuit later.
- Li-Ion batteries do not need to be discharged occasionally all the way down in order to keep them in top condition. Li-Ion batteries do not suffer from "memory". This is only needed for NiCd (nickel-cadmium) or NiMH (nickel metal hydride) batteries.
- Partial discharging and recharging multiple times is better for long battery life than discharging all the way down to where the mod indicates "low battery" and then recharging.
- After charging, let your battery cool to room temperature before using it.
- Don't charge a battery that is below 0°C/32°F. It causes metal to be plated inside the battery eventually leading to an internal short circuit and possibly bursting of the battery.
- Where possible, setting your charger to 4.1V will reduce stress on the battery and extend its life. But you will lose 10%-15% of the capacity of the battery.
- Make sure the charger you use turns off once the charge is complete. Check the instructions for the charger you want to use.
- Never use a trickle charger with Li-Ion batteries! The continuous holding of the battery at the trickle charge voltage damages it.
- Don't overcharge them. To get the longest running possible time from a battery some chargers go up to as high as 4.27V. While this does result in a bit more vaping time before needing to recharge, it damages the battery. Most of the batteries we use are rated at up to 4.25V but even this is quite high. It's not dangerous until we're approaching 5V but battery damage starts occurring way below this.
- Without a separate meter monitoring the battery's highest voltage before the charger stops it's hard to know what our batteries are actually being charged to. Our best option is to have our batteries spend as little time as possible fully charged and charge them just before using them. This usually isn't very convenient but it does extend battery life.
- Charging at a slower rate is better, to a point. Most of our 18650 batteries have a "standard" charge rate of 1.0A-1.5A and a "rapid" charge rate of up to 4A. Charging at 0.5A might help extend the life of your batteries a bit but if the batteries are not getting warm at 1.0A then that's a good compromise between battery life and convenience. Going down to 0.375A or 0.25A won't help much versus charging at 0.5A.
- Charge 18350's at 0.5A until you know that they aren't getting more than a bit warm.
- Charge 26650's at 1.0A until you know that they aren't getting more than a bit warm. The better 26650's can be charged at up 2.0A without adversely affecting battery life.
- Storing batteries in the refrigerator doesn't make much of a difference in battery life unless you live in an area with high temperatures year around. It's not dangerous to refrigerate them but be sure to let them come to room temperature before opening whatever airtight wrapping/container you have them in.
- If a battery wrap becomes damaged, replace it immediately. Replace the top insulator ring if it's also damaged.
- Every time you buy batteries also buy battery boxes or sleeves, wraps, and top insulator rings. You...will...need...them.
***This is the resting voltage, NOT the voltage "under load" that the battery drops to when being used. If your mod stops firing when the battery drops to 3.2V the battery can rise back to to 3.5V or even higher after resting for a while. This "resting voltage" is the important voltage, the one to be used when determining how low you are really discharging your batteries.
While stopping at 3.4V, 3.6V, or even higher might extend battery life a bit you are missing out on a lot of additional vaping time that you could use before needing to recharge. That additional vaping time can be enjoyed every day for, at most, just the cost of one extra set of batteries a year. Stopping at these higher voltages won't hurt the battery though. Just let the batteries sit for an hour before charging to see what their true resting voltage is when deciding how low you want their voltage to go in your mod.
- When you start getting earlier and more frequent "low battery" alerts from your regulated mod even though you haven't increased the power.
- When you notice that your mechanical/unregulated mod doesn't hit as hard, or for as long, as it used to (before needing to recharge your battery).
- If your battery starts getting warmer during use or charging even though you haven't changed power settings or your coil resistance.
- If your charger will no longer get to 4.20V before stopping. Make sure the charger is functioning properly and try switching charger bays before replacing the battery though.
- If you see physical damage to the metal top or can of the battery. Things like dents and deep scrapes should not be ignored! A damaged wrap and top insulator ring can be replaced without needing to replace the battery.
- If the battery vents and leaks fluid, even the smallest amount. Continuing to use a battery after it has vented can lead to the battery overheating and possibly going into thermal runaway and bursting.
- If the battery has rusted badly. You don't need to worry about a few small spots but if they are pushing the wrap up or growing larger then replace the battery.
- If the battery discharged down below 2.0V for a long period of time. Accidentally discharging down below that for a short period of time is ok. But if you left a battery unused for a long period of time and it's now dropped below 2.0V, replace it. You might be able to "recover" the battery with certain chargers but it's probably damaged and it's just not worth it.
- There's no need to replace a battery on a fixed schedule, e.g., once a year. Those who use their batteries at high power levels might have to replace them every few months, or even sooner. Low power vapers can easily get a couple years of use out of their batteries.
- Never throw your battery in the trash! Please recycle it. Many electronics or home improvement stores and vape shops will accept your batteries for recycling. First give the battery a couple of wraps in whatever tape you have to insulate it from any metal it might touch.
- You do not need to replace a battery if you dropped it but there's no physical damage
Inside each battery there are two things that can interfere with the flow of current in or out of the battery. The two of them together are called the internal resistance of the battery.
Why is internal resistance important? It's what causes your battery to heat up and the voltage of your battery to sag.
So what are the two things that add together to create the the battery's internal resistance?
First, it's the actual resistance of the metal contacts and the internal structure that carries current through the battery (the electrolyte, separator, etc.). This resistance is typically only a few milliohms (thousandths of an Ohm) to a couple dozen milliohms.
Second, it's the efficiency of the chemical reactions and flow of the ions through the battery. These ions can't be transported through the battery at any rate we want. As the current level rises there is a difference in the density of the ions in different parts of the battery. This change in the density and distribution of the ions results in a voltage difference between different points of the battery. We see this effect as a voltage change as soon as current flows. Knowing the voltage change and how much current is flowing we can use Ohm's Law to determine the equivalent resistance that would cause the same voltage change.
These two resistances added together (one actual and one equivalent) give you the internal resistance of the battery...or the IR. The "DC IR", direct current internal resistance value, is the one we want to use. Since we pulse our batteries for up to several seconds we want to use the IR value measured when switching between two steady current values, one of them being zero amps in our case because we pulse our batteries on/off.
The "AC IR" value often quoted in battery datasheets is lower but this is something we would use only when measuring performance in an unregulated PWM device. It's measured by pulsing the current at 100Hz or 1000Hz.
The typical DC IR (which I'll just call IR) of a new Samsung 25R battery at room temperature is roughly 0.022-0.025 ohms. For a high-capacity 5200mAh 26650 battery the IR can be as high as 0.06 ohms. This is what causes the large voltage sag when we try to vape with these high-capacity 26650's at higher power levels.
The IR of a battery affects how we vape by causing the voltage to sag during discharging and the voltage to rise during charging. Since these voltage drops or rises are just temporary, and aren't the true voltage of the battery, this can be a problem.
So how does IR affect us when vaping? What other problems does it cause?
We'll cover this in a future article.
Calculating the current being drawn from the batteries in a regulated device can be very confusing. You can't do it the same way as you would for a mechanical/unregulated device and there are so many different battery configurations; single, dual parallel, dual series, triple series, etc.
The way I keep it all sorted out is to remember that, in a regulated mod, the coil isn't connected to the battery. The regulator is. To calculate the current being drawn from each battery when using variable-wattage (VW) mode you need to calculate the maximum wattage each battery supplies.
Here's how I do it...
As an example, the RX200 has a maximum wattage rating of 200W. Since it uses three batteries that means each battery supplies 200W / 3 = 67W. For dual parallel or series 150W devices each battery supplies 150W / 2 = 75W. You use this method for series or parallel devices, it doesn't matter.
Once you have the maximum wattage for each battery then you can use the following formula to determine the maximum amount of current that can be drawn from each battery...
Max Amps Per Battery = Max Wattage Per Battery / Minimum Voltage Per Battery
For the RX200 the minimum possible cutoff voltage is 9.0V, which is 3.0V per battery (unless you set the cutoff higher). For most other devices the minimum is 3.2V or 3.1V per battery. Let's use the Sigelei 150W TC device as an example. This device has a minimum battery voltage of 6.4V, which is 3.2V per battery...
Max Amps Per Battery = 75W / 3.2V = 23.4A
So you want a battery that can safely supply 23.4A of current if you're using the mod at its maximum rating of 150W.
I should add that to get as close as possible to calculating the max current being pulled from your batteries you should add an additional 10%. This will account for the inefficiency of the regulator. For example, if your device draws 23.4A then add 2.34A for a total of 25.74A. Not a big difference, but it's there. That changes the equation to...
Max Amps Per Battery = (Max Wattage Per Battery / Minimum Voltage Per Battery) / 0.9
If you know you will not be exceeding a particular wattage that is less than the maximum then you can use that wattage in the equation instead. This often means you're able to use a higher capacity battery like the HG2 or 30Q instead of a high current rated, but lower capacity, battery like the VTC4 or HB6. It's worth doing the math to find out.
This works for series or parallel devices. It does not matter how they are connected as we are already taking that into account when we calculate the max power for each battery.
It takes much longer to explain all this than it does to actually calculate the amount of current being drawn from your batteries. I hope this helps make the very confusing process of determining how much current is being drawn a little bit easier.
Have you considered using a battery because of its high pulsed current rating? At first glance the pulse rating seem to make a lot of sense. After all, when we vape we don't run our batteries continuously. We only use them for a few seconds at a time. And considering how much higher the pulse ratings are, versus the continuous current ratings, it's very tempting to choose a battery based just on its pulse rating.
There are no standards for these pulse ratings. One battery reseller could base their rating on taking 4 second draws every minute and another might base their rating on 10 second draws every 20 seconds. These two examples will result in very different temperatures and performance. The same battery could get a 40A rating one way and a 30A rating the other way. This makes comparing batteries by their pulse ratings very difficult, if not impossible.
But that's not the worst of it!
What happens if our regulated mod autofires or our mechanical mod's button gets stuck on or accidentally pressed in our pocket? If we have set up our mod with a low resistance coil that forces us to only rely on a battery's pulse rating, we could be in big trouble. We could easily overheat the battery, causing it to vent or perhaps even burst.
Choosing which battery is best to use based on pulse ratings is not only practically impossible, it can be unsafe too.
So how should you choose a battery to get both the most power for your mod and still be safe? Either go by the continuous discharge rating (CDR) or find a reviewer that tests batteries beyond the CDR and records temperatures to know when it becomes unsafe. But for longer battery life, consider running your batteries below their CDR. It adds a greater safety margin as the batteries age and lets them run cooler.
I have set up a table of safety "grades" for all the batteries I have tested to date. This table shows you what discharge current levels are safe and which might be dangerous for each battery. It can be used as part of choosing which battery might be best for you:
18650 Safety Grades -- Picking a Safe Battery to Vape With
For more detailed information on the batteries I've tested, here's a list of links to the results of each test:
List of Battery Tests
If you're considering using a battery that has a rating above 30A, check this out before you buy them:
There are no 18650 batteries with a genuine rating over 30A!
We've all seen them, the batteries with 35A (35 amp) or higher current ratings. And it seems that they would be the perfect choice for mech (mechanical mod) users or really low ohm coil builds, doesn't it?
Except for the fact that as of July 2015 January 2016 there are no 18650 batteries rated at above 30A continuous available to us vapers!
Batteries are manufactured by only a handful of companies like Samsung, Sony, and LG. It takes millions of dollars to start up even a modest battery production line. The companies you see selling these high-amp batteries are just too small to be able to afford that kind of investment. So where do they get the batteries from? The established battery manufacturing companies like Samsung, Sony, and LG!
These smaller companies buy the batteries, rewrap them (i.e., they put their own "wrap", or sleeve, on them), boost up the current and capacity ratings, boost up the price too, and sell them as high performance batteries. This is how we know that there are no 35A or higher rated 18650 batteries out there. None of the big battery companies make them!
Since these battery rewrapping companies use the same batteries that we can buy at a lower price with the original manufacturer's wrap still on them, why should we buy them? In my opinion, no reason at all unless they are the only ones you can get.
Can these 35A and higher rated batteries actually be used at those high current levels? Technically, yes. Those high current ratings are just "pulse" ratings, passed off as continuous current ratings. This means those batteries can only be used at those current levels for short pulses of current. You might be thinking that this isn't a problem because we only vape for a few seconds at a time. But using them like that isn't safe.
Since battery rewrapping companies typically exaggerate the ratings by quite a lot, or pass off the pulse rating as the continuous current rating, we don't know how hard we can safely run those batteries continuously. And this can lead to big problems if we have a regulated mod that autofires or if we have a mech mod and its button sticks or is accidentally pressed in our pocket. Without knowing the battery's true continuous current rating this could easily lead to the battery spraying hot, toxic stuff inside your mod ("venting"). Or worse, it could cause the battery to go into "thermal runaway" where the temperatures rise tremendously and the cell violently bursts open.
To help you figure out how hard you can run different batteries, take a look at my 18650 Safety Grades table. It can help you narrow down your choices:
18650 Safety Grades -- Picking a Safe Battery to Vape With | E-Cigarette Forum
For some great information on batteries and battery safety (and many other topics), see Baditude's blogs:
(18) Baditude's Blogs | E-Cigarette Forum
And don't be afraid to just ask for advice here at ECF. If you see a battery that you want to buy, but aren't sure if it's safe to use in your mod, please ask us! We want to see everyone vaping safely and will be glad to help.
So, are there 30A batteries? Only one, the LG HB6 1500mAh 18650. You can see the classic tradeoff between capacity (number of mAh) and the current rating here. Typically, if you want high capacity you can't have a high current rating. And vice-versa. If you see a battery with both, check around for test results or a review before buying it.
There are other batteries that handle almost as much current as the HB6 though. I recommend the Sony VTC4 as the best all around battery for over 20A. At around 20A it's hard to beat the Samsung 25R. Just be sure to buy from a reliable vendor that carries genuine batteries, like one of these (in no particular order)...
So be careful of these batteries boasting that they're rated above 30A and vape safe!
This blog is my personal opinion only and is based on my battery testing results and knowledge of the batteries that are available on the market. If you are a vendor or supplier with a battery you are confident has a continuous discharge rating over 30A, I would be happy to test it and post the results.