Bare cell batteriesThis guide is for cylindrical bare cell lithium ion batteries that charge in a dedicated charger EG 18350 & 18650 batteries. You should ALWAYS follow the manufacturers instructions and this guide is not intended to replace them. This guide has been prepared by forum members who have taken care to accurately research the information provided, but it is provided for use at your own risk and neither the forum or the members who contributed to this guide accept any responsibility or liability for the accuracy of the information or advice nor for any consequence that result from following the advice.
Do's and Don'ts• NEVER leave a Li-ion battery charging unattended or charge while sleeping (these batteries do not have a memory effect so just disconnect and charge them again later).
• NEVER leave an e-cig or e-liquid where pets or young children can get to it.
• NEVER leave your battery in direct sunlight or in other hot locations like your car or near the cooker.
• NEVER carry your battery loose always carry in an insulated container.
• NEVER charge in temperatures below 5 °C, this will affect the long-term safety of you battery.
• NEVER charge in temperatures above 35 °C, this risks starting a fire.
• NEVER charge with a lead or power supply that is damaged.
• NEVER charge near heat sources like a hob, dishwasher or strong light source, including in your car in bright sunlight.
• NEVER charge near flammable items like curtains, soft furnishing or paper.
• NEVER charge where your battery or power supply could get wet E.G next to the kitchen sink.
• ALWAYS disconnect your battery from the power supply as soon as it is charged E.G. light turns green, and unplug the power supply from the mains.
• ALWAYS charge on a non-flammable surface like a ceramic plate or in a LiPo safety pouch.
• ALWAYS charge in an area where there is a smoke alarm.
• ALWAYS store your in a mild temperature 5 °C to 25 °C.
• ALWAYS store your batteries in insulated containers where there is no chance of them moving about.
• ALWAYS dispose of old or damaged batteries safely. Do no bin them. Ask your local council where to take them, usually it will be one of their own facilities.
ALWAYS dispose of your battery if:• It becomes unusually hot, they can get warm especially when you keep them in you hand during use.
• It has been damaged I.E. dented or punctured, leaks any liquid or emits any strange odours.
• It has been submerged or dropped into water, DO NOT charge the battery even if you have dried it out.
• It does not hold a charge overnight.
• It has lost significant capacity.
Tips• Store your batteries in a non-conductive container in a cool place away from flammable materials, ideally at around 40% charge for longer term storage, but never store them when fully discharged for long.
• Keep a record of the date you obtained each battery, label them ideally as it will help you cycle them and predict when they are coming to the end of their life.
• Unscrewing your atomiser adds an extra level of safety over locking your battery when carrying in a bag or pocket.
• Your batteries do not like the cold, they will not work well in freezing conditions.
• Having more than one battery not only gives you a backup but allows more flexibility and makes it easier to find a convenient time to charge the spare while you can be there in case anything goes wrong.
• Let your battery rest for an hour or two after charging if possible.
Types of bare cell Bare cells typically come in two basic forms for e-cigs: cylindrical LiIon or LiPo packs and this guide will only cover the far more common cylindrical LiIon cells.
Cylindrical LiIon cells come in various sizes denoted by their type number EG 18650, the first 2 digits are the diameter in mm, the 3rd & 4th digits are the length in mm and the last digit would be the first decimal of the size though never used according to
Cardex and others. Each size can also come in button or flat top (positive terminal). Often batteries are not exactly the size denoted by their number so it is worth checking before you buy for a specific device. Protected batteries that contain a circuit board normally at the bottom are generally longer, but few people would advise the use of these in e-cigs these days.
mAhThe next number you will see associated with the battery is it's capacity normally in milliamp-hours (mAh) and is how many milliamps the battery can supply in an hour. It is not a perfect way of judging capacity, but is the standard. High capacity batteries will have a low maximum safe current and high drain or high safe current will have lower capacity. The highest capacity have the lowest discharge currents and vice versa.
Discharge current ratingsThe maximum discharge current is a very important number associated with your battery which tells you how many amps the battery can safely supply, you should never go beyond this and will get more usable power if you are at 2 or 3 times the current limit because at these currents the battery voltage will sag under load (go down when fired). This does not only apply to mechanical mods but the vv & vw devices too, a good rule of thumb would be max amps required = wattage x (10/9) / 2.5 so a 50 W mod would need at least 50 x (10/9) / 2.5 = 22.2 A. You will get more usable power if are at 2 or 3 times the current limit because at these currents the battery voltage will sag under load (go down when fired). There is also a maximum discharge current which applies to short bursts (how short varies between manufacturers) and is up to twice the previous figure, don't use this number as a limit it is not safe, if your device gets accidentally activated or stuck on bad things can happen. Unfortunately some manufacturers and vendors have started only quoiting one number and choose the least safe one so be very careful when selecting a high drain battery and do your research or ask on the forum.
A good approximation of the current needed in a variable wattage device is the watts divided by 2.5, for unregulated devices it is 4.6 divided the resistance of your atomiser (4.6 rather than 4.2 gives a 10% margin).
Charge current ratingsBatteries also have a charge current and fast charge current rating, sometimes this in expressed in C rather than Amps to get amps multiply the C rating by the capacity in mAh and divide by 1000 EG a 0.5 C 2500 mAh battery would bee 0.5 x 2500/1000 = 1.25 A. If you can not get the charge current assume 0.5 C and don not exceed 1 C. Never charge above the fast charge current and this may shorten the life of your battery and will probably make it hot. For the best life time charge at the charge current and charge before the battery is empty.
Internal resistanceA low internal resistance is also important especially for high power set ups and affects battery sag, but beyond the scope of this guide.
Battery chemistriesThese batteries come in a variety of types or chemistries which we will not go into any detail about, but there will be links at the bottom for those interested. For vapers there are two important groups: safer chemistry (IMR & IMR-hybrid) which are also high drain and everything else. Typically safer chemistry batteries have manganese oxide in cathode material, but manufacturers are constantly developing the technologies. For mechanical mods and high powered regulated devices (> 15 W) only use safer chemistry high drain batteries. Decent lower powered devices like the Z-Max, VTR, eVic ect have safety circuitry so can use the lower drain high capacity batteries. As said above protected batteries are not a good choice and many regulated devices can not use them.
I have not recommended specific batteries as this changes too often, just be clear about which of the two groups your needs fall into, check if your device can only use one of flat or button top, if you need high drain batteries know the minimum safe continuous discharge current you need and use a trusted vendor. One Internet e-cig reviewer recently claimed that most e-cig wholeslaers in the USA unknowingly sell fake bare cells and that you should only buy from retailers who use a specialist battery wholesaler.
Dual battery devicesThese come in two configurations: series or parallel. With both you should buy the batteries together, keep them together as a set and if one fails replace the whole set with new ones. It is extremely important to ensure that parallel batteries are all the same voltage when putting them in to your device or else very high currents can result in charge from the high ones going into the others. With series batteries periodically check the voltages when removing them they should be within 10 % of each other and the lowest should be above 3 V, preferably 3.3 V. There is a myth that you need to rotate the order of series batteries, do it if you want it won't do any harm, but there is no need to. Series battery packs are in millions of products from cars to power drills and no evidence that the top battery is under more strain than the others, it may drain a vary little faster if it is made hotter by the atty.
ChargersNever skimp on your battery charger, stick to brands like Xtar, Nitecore & Pila from trusted vendors, even though LiIon batteries are one of the simplest to charge small inaccuracies can have big consequences. Most LiIon batteries are rated at a maximum voltage of 4.2 V and safety limit of 4.25 V - 4.3 V, that is a 1.2% - 2.4% tolerance so chargers must measure this vary accurately and err on the side of caution by undercharging rather than overcharging. The tolerance of the actual battery is even tighter at +/- 0.05 V or 0.12 %.
LiIon batteries don't need a trickle charge like other batteries, in fact it will damage the battery and is dangerous. LiIon batteries are charged by a constant current constant voltage algorithm (CC/CV) the bulk of the charging is done in the first constant current phase and this is the current that relates to your battery and charger specifications. This phase will charge the battery to around 70 % then the charger switches to constant voltage or saturation phase which can take longer than the first phase especially at higher currents, doubling the charge current will not halve the charging time. During this phase the current is steadily reducing until the battery is full, this can be observed by plugging your charger into a mains power meter.
At minimum a charger should have a status indicator to show if the batteries are charging, charged or can not be charged. Having several charge current rates is a very useful feature especially if you use different battery sizes. Having gauges, currents and voltages on a nice screen is nice, but not necessary. There are chargers that can measures the battery capacity and some that measure internal resistance although not very accurate they can be useful for assessing the health of your battery
Some chargers like the Nitecore i4 and EFest LUC4 (most 4 battery chargers) and many others have two charging circuits shared between the 4 battery bays, sometime this is referred to bays being paired. When charging 4 batteries the charge current is often halved and when charging two you need to check the instructions to see which two bays to use to get the full charge current (one from each pair or charge circuit). This could also be the case with cheap 2 battery chargers.
Some chargers like the higher range Xtars have a revive feature that can charge batteries that have been over-discharged which initially charges with a low current until the battery gets back the the normal empty level and then charges normally. Multi technology chargers like many of the Nitecores charge several types of battery EG NiCd, NiMh & LiIon will not have a revive feature.
AWT do chargers that have capacity and internal resistance measuring functions that can be useful to try and tell if your battery is coming to the end of it's life.
Charging your batteriesChoose a sensible location away from any heat sources like radiators, washing machines or direct sunlight and put your battery on a flame proof surface a ceramic plate before you start. If you have the manufacturers guidance on charging then follow that, but usually you turn off your battery, connect it to the power supply and turn on the mains power if it is mains powered. Some devices have a screen that will show the charge progress in a battery graphic and some just have a multicoloured status LED. The exact meaning of LED colour codes and flashes varies from model to model and there should be information from the vendor or manufacturers about what they mean.
If you need to leave the room where you're charging for more than a few minutes it is safer to turn the mains to the charger off and disconnect the battery, you can resume charging when you get back and it won't shorten the life of your battery. If you are unwilling to do this then consider a LiPo Safe or LiPo Guard charging pouch that will provide some protection in the event the battery vents, flames or explodes and charge in a room with a smoke alarm.
Once charging is complete disconnect everything and if you have another battery that is only half empty it may be more convenient to charge that now if you are going to be out and about later.
Battery working lifeThe life span of lithium batteries depends on many factors including number of discharge cycles, age and heat exposure. Average life expectancy is about 2 years and 300-500 charge cycles for good quality lithium batteries, note that age is a factor so avoid buying old stock.
Charging to 90% full (approx 4.1 V) can double the life span of your battery, charging to 80% can give your 4 times the life and charging to 75% can give you 8 times the life span. Unfortunately commercial battery charges don not allow you to choose the final voltage currently and strangely charging even slightly below 4.2 V is seen as a negative by many users and vendors. Draining your batteries to empty also shortens their life, the effect is not as much as for charging, discharging to 50% only prolongs the life time by a factor 4 which is the same saving as charging to 80%.
Charging at unsuitably high current (amps) or using (draining) at high current that causes your battery to get too warm will shorten its life. Avoid charging a battery faster than 1 C and a more moderate charge rate of 0.7 C is preferred (C Rate is the mAh divided by 1000). Some high drain batteries are built to run warmer than others.
Store your batteries at around 40% charge if they are not in use for a week or more. Over 3 months at 25 °C your battery will lose approx 4% of it's capacity when stored at 40%, but when stored at 100% charge it would lose approx 20% of it's capacity in the same time.
Storing at unsuitably high temperatures will shorten it's life, try and keep them below 25 °C. In comparison at 40 °C your battery will lose approx 15% of it's capacity when stored at 35%, but when stored at 100% charge it would lose approx 20% of it's capacity over 3 months. This applies to laptop batteries too, so if you only use them plugged in drain the battery to 40% as store it below 25 °C to extend it's life.
Thermal runaway in Li-ion batteriesLi-ion batteries contain flammable material, store very high levels of energy and some are pressurised. If overheated they can suffer thermal runaway producing a dangerous build up of extremely hot flammable gases. Cylindrical metal cased Li batteries normally feature a pressure release safety valve that will allow these gases and possibly liquid to escape before the casing ruptures, known as
venting and even flames in extreme cases
flaming, but if the pressure valve fails to open, is not included or your device does not have sufficient venting a rapid disassembly (explosion) can result. If venting occurs the hot spots inside the battery can potentially continue to heat until the battery combusts or dissembles (explodes).
Thermal runaway can be caused by drawing too high current from the battery this could be a short circuit or running at too high wattage, charging the battery at too high current, charging the battery above it's maximum voltage, heating the battery, physical damage or shock to the battery amongst other causes. Manufacturing defects and poor design can also cause thermal runaway at any time so it is important not to risk using low quality batteries and always purchase from trusted vendors to avoid counterfeits. There are also features the best manufacturers build into LiIon batteries that reduce the risks. There are other potential factors that can cause thermal runaway mentioned in the do's and don'ts section above.
IMR and safer chemistry batteries vent less violently than standard LiIon batteries and thermal runaway can often be stopped if caused by external circumstances EG a short circuit if the cause is rectified before reaching around 250 °C on the best IMRs, but standard LiIon's will continue after they have reached 150 °C degrees. This and high discharge current capability are why IMR and safer chemistry batteries are recommended in e-cigs, the protection circuit on protected batteries is not guaranteed to work, can be destroyed by static or high voltage spikes and as it draws a small current it can discharge your batteries in storage to the point that they will not recharge. There is a trade off they have lower capacity and life span.
If your battery does get too hot take it outdoors and leave it in a safe place to cool if possible and keep pets away from it, then dispose of it once cool. If your battery flames or catches fire use a dry content fire extinguisher if possible or if not available water (be careful of electrical hazards such as a charger still connected to the mains). The FAA recommend immersing it in water too cool a burning battery, but
RCHARGE warn of electrical hazards from large battery packs and surrounding equipment.
More guides on AAE-C
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Battery buying guideConsiderations when using a MechEureka! Volts, Ohms and Watts 101Further informationSafety Concerns with Li-ion Batteries – Battery UniversityCharging Lithium-ion Batteries – Battery UniversityHow to Prolong Lithium-based Batteries – Battery UniversityCharging from a USB Port - Battery UniversityWhat is the C-rate? - Battery UniversityBattery UniversityBatteries in a Portable World 2nd EdRECHARGE Then European Association for Advanced Rechargeable BatteriesECF battery pageTypes of Lithium-ion Battery - Battery UniversitySerial and Parallel Battery Configurations - Battery UniversityProtection Circuits - Battery UniversityCharging without Wires - Battery UniversityShipping Lithium-based Batteries by Air - Battery UniversityCycling Performance - Battery UniversityBattery venting and mod design - ECITABattery venting and mod design part 2 - ECITALi-Ion protection technology and possible dangers - CandlePower forumBattery Basics for Mods: IMR or Protected ICR - ECFWhat exactly does IMR mean - CandlePower forumSmoke and Fire, Hot Cells and Close Calls - The dangerous side of batteries from CandlePower forumLygte battery and charger reviewsBatteries Explained and Safety - VapeTVLithium-ion Battery - WikipediaEEVblog #176 - Lithium IonPolymer Battery Charging Tutorial - YouTubeLithium Assembly Design & Trends - House of Batteries - YouTube
