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Rechargeable Batteries

Discussion in 'The ECF Library' started by rolygate, Oct 14, 2010.

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  1. rolygate

    rolygate Forum Manager Verified Member ECF Veteran

    Supporting member
    Sep 24, 2009
    ECF Towers


    The Battery Page

    This page is a reference section for battery information relevant to e-cigarette use - and especially for APVs (e-cigarettes with large, user-replaceable generic rechargeable batteries, usually with one or more features or functions not available in a mini e-cigarette).

    Part 1 - this post
    Part 2 - next post

    To edit / add to this page, see at foot.


    General advice


    Use a safer-chemistry battery such as Li-Mn or hybrid

    Note 1: we no longer recommend protected Li-ion (ICR) as an automatic choice.
    • IMR (Li-Mn) or hybrids are now (2014-03-21) a far better choice for all removable-cell devices of any kind: mechmod APVs, electrically switched APVs, and electronically-regulated APVs (VV and VW).
    • ICR (protected Li-ion) is now for specific, well-chosen applications and generally means a low current draw of <3A is required.
    Note 2: we no longer recommend Li-FePo4 batteries.
    • They require a special charger, or the switch on a dual-voltage charger to be correctly positioned - which means mistakes will be made.
    • They are a commonly counterfeited battery, and could be re-covered reject unprotected Li-ion cells instead of Li-FePo4 - it may be impossible to verify the supply chain or what the battery really is. Because these cells are normally used in series, there is a significant elevation of risk with counterfeit cells.
    • Although they are probably the most stable of all lithium cells, their heyday was back when 2-cell mechmods were popular for 6 volt vaping, and that time has gone. They have few modern applications in vaping.

    (often called 'lithium camera batteries')

    Mechmods (mechanical APVs) with RBAs (rebuildable atties) may not work with a protected Li-ion cell because the current demand is too high. A safer-chemistry cell is a better choice.


    Rest batteries after charging
    One commonly-reported factor in almost all the incidents we hear of where batteries failed violently while in use is that they were taken directly off the charger and then used immediately, at which point they failed.

    Because of this, we think it may be a good idea to rest batteries after charging them. This advice will not be found in the usual 'reference bibles' on batteries, but we see more and different reports than others. Therefore we now advise:

    Do not use batteries directly after charging them. Use a battery or batteries you previously charged, and that have rested for several hours. This is especially important if using a stacked pair for higher voltage, as statistically the risk is far higher.


    Our advice is that the best and the safer choice of battery for APVs is the AW IMR Li-Mn rechargeable.

    It is a safer-chemistry battery that needs no protection, and has a high-discharge rating meaning that it is safer to use with high-current devices such as atomizers. Here is a good post on battery safety that lists many safer-chemistry batteries and their specifications:
    (9) Battery Basics for Mods: IMR or Protected ICR? | E-Cigarette Forum


    Many think the best option is the largest AW Li-Mn battery that can be fitted (this is partly due to the fact that the supply chain can be verified if due diligence is used). Other safer-chemistry cells where the supply chain is verifiable are an equally-good choice; counterfeit batteries are a problem because the label is false and therefore the battery could be anything.

    But please note that no lithium rechargeable battery can be regarded as 'safe' - that simply is not possible. When we refer to 'safer', we mean the reduction of the possibility of blowing up in the face of a user who has just taken the battery off charge and is applying a heavy current draw to the device. An atomizer is regarded as a heavy current draw for this size of battery. No other definition of relative 'safety' is inferred.

    Lithium batteries of all types are all capable of catching fire if mistreated. This might be by overcharging due to a faulty charger; being placed in a confined space and shorted out (such as in an APV, in a pocket, with the master switch not set to off and either the on button pressed continually or an internal fault in the unit); or similar mistreatment.

    Rechargeable lithium batteries are not safe in an absolute sense and should never be regarded as being so.
    While eGo-type batteries are ideally recharged in a Li-Po charging sack on a fire-proof surface such as cement, stone, tile or brick, the best solution for removable batteries is probably in a cake tin (aka biscuit tin) with vent holes drilled in it (as the charger will not overheat).
    NEVER leave cells unattended while charging.
    APVs need basic safety features such as a locking actuator switch (good) or a master on/off switch separate from the main actuator switch (best), and some form of gas vents.
    Two-cell non-electronic devices should have substantial gas vents (electronic devices are safer as they provide fusing that cannot be bypassed).
    If you choose to ignore these points then you must accept the consequences.

    Lithium rechargeables are not absolutely safe, and neither is an APV with them in. No statement anywhere on ECF may be taken to mean that any particular make of battery is 'safe'. Safe is not a term that can be used for lithium ion cells, which have well-known risks. Some are much safer than others, though, and IMR or hybrid types are safer than ICR cells of any kind.

    Battery fires
    The most common type of battery fire occurs with mid-size (eGo type) units on charge. The next most common, although less frequent, are battery pocket/purse fires where a loose cell was being carried, and the battery shorted out on coins and keys. Don't carry batteries loose - get a battery box (eBay) or an ecig case.

    A note on IMR, ICR and hybrid
    IMR means Lithium Manganese. In fact it is a misnomer because although we say "i m r" it should be "L m r", as it refers to 'lithium manganese rechargeable'. The font used caused a confusion between L and I, but it's too late to change now. Lithium manganese cells are a safer chemistry type that need no protection circuit on the battery itself.

    ICR means Lithium Cobalt. The same confusion has occurred with L and I. Lithium cobalt cells are the regular Li-ion type that need a protection circuit added on to the negative pole of the battery in order to achieve acceptable safety. They are then called a 'protected battery'. The basic chemistry of these cells means that they are not as safe as IMR cells. They cannot be used in high current draw applications either, because although the bare cell can cope with high loads, the tiny electronics in the protection circuit cannot, and there is a maximum practical limit of 2 or 3 amps.

    ICR cells are obsolete now, and there is no reason at all to choose them. There is one possible exception: where a low current draw is needed over an extended period of time, they can sometimes be the best choice. In other words, if you vape at 1.5 amps and want a cell that will last slightly longer between charges, then this is about the only profile that benefits from an ICR cell. In practice they are almost always a poor choice.

    Hybrid cells are a combination-technology variant where (generally) Li-Mn is combined with another type. They are a safer-chemistry type that can deliver high current.

    Battery counterfeiting
    This is a growing problem and all APV users need to be aware of it.

    This is what happens: the counterfeiters buy reject Li-ion batteries in bulk, strip the covers off, and re-cover them with labels that change them to look like popular brands. In this way they can take a cell bought for 10 cents, re-work it, and sell it as for example an AW battery with a retail price of $10. The profits are very high and this practice is growing. It means that you never really know what battery you have unless you buy from somewhere with a verified supply chain. For example, all AW batteries offered for sale on Alibaba are counterfeits, and possibly dangerous.

    Buy the best batteries
    Please don't try to save money on batteries, it is the worst possible area to make economies. It's like trying to buy the cheapest possible parachute, with no idea where it comes from or who made it, and pretending there is no increase in risk. Why would you do that?

    Only use safer-chemistry rechargeables such as Li-Mn or Hybrid in an APV.
    Protected rechargeable Li-ion batteries, or high-quality Li-FePo4 can also be used for specific applications.
    Suitable batteries of any type generally have a C rating of greater than 4C or 2 amps or 2,000mA, and this should now be regarded as the absolute minimum [see Note 1].
    For single-cell VV or VW electronic devices, the C rating needs to be at least 5 amps (more is better).
    For RBAs the C rating must be very much higher, and 10 amps is regarded as the minimum for safe operation unless the current draw is kept low by keeping the coil resistance high.

    Primary and secondary cells
    A rechargeable is also called a secondary cell. An ordinary, non-rechargeable battery is called a primary cell.

    Lithium rechargeables (of any kind) are normally called lithium ion cells. Only use rechargeable batteries. Never use standard batteries (primary cells) in any kind of APV. Standard batteries = stock cells / primary cells / ordinary batteries. This is because they can be mixed with rechargeables by mistake, put in a charger, then used in an APV - resulting in an explosion on first operation of the device (and this has happened). Charging a primary cell often results in fire or explosion, and the main risk is that this can occur on first load demand.

    This can also occur with an unprotected Li-ion rechargeable of course - but the explosion with a standard battery is especially violent as there are no gas vents built in to the battery. In one explosion of an APV involving standard batteries that had been recharged by mistake then used in a 6 volt device, it was reported that a broken jaw and lost teeth were caused.

    Explosions may be due to thermal runaway when a faulty cell is overcharged then put in an overcurrent situation (which atomizer use frequently is, since most small cells cannot safely provide enough power for an atomizer, which might draw 2.5 amps). Protected batteries have a small electronic package built in that trips out in case of various fail modes. However Li-Mn (and some Li-FePo4) batteries can handle heavier loads safely.

    The more batteries and the higher the volts then the higher the risk. Incidents have occurred with a single unprotected battery, but when they are placed in series the risk is higher. Statistically, 2-cell 6 volt+ mechmod users are more likely to experience an incident, and are the only group experiencing explosive incidents*. Battery fires occur in even the most expensive VV devices - basically it is impossible to completely prevent them with lithium cells (phones and laptops have thousands of such fires).

    * Update Q3 2015
    We have now seen some explosive incidents in 2015 with 1-cell 18650 mechmods and RBAs. This appears to be due to super-high current draws exceeding 50 amps or possibly even in the 100-amp range, when using ultra-low resistance coils for cloud chasing. Perhaps the batteries were counterfeits although at this stage it is impossible to say. There is some basic advice that can be given here although it is very likely that those who most need it will not take any heed of it:
    • If using coils of 0.2 ohms or below, more safety precautions are needed (for example you must be very sure your battery is not a counterfeit or a cheap product)
    • Metal tube mechmods pulling super high amps need substantial gas vents in case of a fault that leads to a battery failure
    • A 26650 cell is intrinsically safer for this type of ultra high load duty as it is bigger and can take more abuse before failing (we have no reports of a 26650 cell failing violently)

    The highest risk of all is the use of two batteries in a metal tube APV that appears to be sealed. This is partly because you do not know what those batteries are, as counterfeiting is so widespread now. IT IS WHY METAL TUBEMODS MUST HAVE OBVIOUS SAFETY FEATURES SUCH AS VERY LARGE GAS VENTS with the possible exception of fully-electronic models as they have no serious incident history. Assume that your two batteries are cheap reject (faulty) unprotected Li-ion cells - BECAUSE THEY COULD VERY WELL BE, no matter what it says on the label.

    Li-Mn or hybrid cells are intrinsically safer and in any case will deliver far more current for modern applications than protected Li-ion cells.


    [Note 1]
    There are now some forms of safer technology batteries such as Li-Mn, Hybrid and some but not all Li-FePo4 - see below - these don't need protection circuits built in. It may be wise to build a protection circuit into the APV though, as they can discharge a very high current in a short-circuit* condition.
    * A 'short-circuit' = a 'dead short' = a 'short' = a direct connection between the positive and negative terminal through the device's casing or circuitry



    Rechargeable batteries

    We now advise that Li-Mn or Hybrid rechargeables are used in APVs, in preference to protected rechargeable Li-ions. We suggest the best option, in order, is:

    1. AW IMR Li-Mn rechargeables.
    2. Panasonic or similar hybrid cells. (Sony spinel cells are new on the market at the date of edit [2013-09-01] and it is likely they will also prove acceptable, they are an Li-Mn type). You must ensure that these cells are sourced from an authorised distributor, as they will become extensively counterfeited.
    3. AW Li-FePo4 rechargeables [Li-FePo4's mostly NEED A SPECIAL CHARGER]. Note that these batteries are mostly 3 volt nominal so the system voltage will be lower than normal. They are the best choice for stacking as long as they are not counterfeits.
    4. Good quality (such as AW or Pila) protected Li-ion rechargeables.
    5. Branded protected Li-ions come next - such as *fire Li-ion rechargeables (for *, insert Trust / Sure / Ultra-).
    6. The least-preferable option is a generic protected Li-ion.
    7. Unprotected rechargeable Li-ion cells should not be used.
    8. Standard cells (non-rechargeable) MUST NOT be used.

    Li-FePo4 cells can be used provided that they are top-quality, ideally they should have a rating of 4C or higher. They are only suitable for specialised applications now.

    If using Li-ions then protected rechargeables are advised, as standard 3.7 volt Li-ion lithium rechargeable batteries can explode under certain circumstances which protection circuits generally prevent (over-charging, short-circuit, over-discharge, over-voltage). Thermal runaway (leading to violent de-gassing or explosion) sometimes occurs with these batteries, as they generally have a 1C rating, that is to say, the discharge rate is 1x the capacity - which is not enough reserve power to efficiently power an atomizer, which demands more amps than a small Li-ion battery can effectively deliver (about 4 or 5 times more). This means they are being overstressed. An over-charge incident followed by a high-current demand may result in thermal runaway - in other words the battery may explode on first use after recharging.

    This is not a frequent occurrence - but it does happen. Note that the likelihood of this particular fail mode occurring can be minimized by using the largest batteries possible, since they are not then overstressed. More incidents occur with small batteries like the RCR123 than large batteries, probably for this reason.

    Protection circuits trip out and usually stop these events. The protection circuit is built-in to the battery - the copper surface you can see at the negative end of the battery is the bottom face of the circuit board the electronics are on. Protected batteries are therefore physically longer than their unprotected cousins, as the circuit board has to be added to the lower end of the cell.

    However, there are some batteries such as Li-Mn, Hybrid and Li-FePo4 that do not require on-battery protection as their chemistry is safer [see #1 above]. These batteries can still present risks in some circumstances (if short-circuited for example). As they are not available in protected form, protection should be incorporated into the device. These 'safer chemistry' types are not known to explode, but will go into meltdown with flames if abused.

    Li-Mn or hybrid cells are intrinsically safer and in any case will deliver far more current for modern applications than protected Li-ion cells.


    Rechargeable battery types

    Li-ion rechargeables
    These batteries are in fact Li-CoO2 (aka Li-Co), lithium cobalt dioxide. The nominal voltage quoted is 3.6 or 3.7 volts, which is the same thing - there is no general agreement on whether to call lithium cells 3.6v or 3.7v cells. The 3.7 volt rechargeables are the basic unit used in APVs.

    It is safer to use the protected versions since Li-ion batteries are vulnerable to thermal runaway and violent out-gassing or even explosion in some fail modes, which are probably due to a chain of three faults such as faulty batteries, overcharging, and overdriving. The hot gas expelled is a mix of hydrogen, methane and ethylene, which will not ignite in anaerobic state (without air/oxygen) but burns fiercely as soon as it contacts and mixes with the oxygen in air. The main risk is with using two batteries in series ('stacking') in an APV with no safety features. Since an explosion is likely to be right in front of the user's face on first use of newly-charged batteries when energising the atomizer for the first time, some nasty injuries can AND HAVE been received. A small number of people have been severely injured, and others have received minor injuries. Don't use unprotected Li-ion cells, and make sure your APV has safety features.

    One incident that occurred to a flashlight (torch) user resulted in lithium poisoning lasting several days, from chemical inclusion in the wounds resulting from an explosion. Flashlight users have been using lithium cells (and in sealed-unit high-power applications) for much longer than ecig users, and have the best data on lithium cell incidents since they have experienced hundreds or perhaps thousands of them. See the Candlepower forum, for example.


    A Li-ion battery has no 'charge memory', so it can be charged at any point of the discharge cycle with no ill-effects. It does NOT need a long first charge, or a 'conditioning' first-use full-discharge then a full charge. These are memory effects seen in other battery types such as Ni-Cad and DO NOT APPLY to Li-ion batteries. It's true that a cell may not work at full capacity for the first charge or two but this is not a memory effect.

    These batteries are a nominal 3.6 or 3.7 volts (which is the same thing). They are charged fully at 4.2 volts and best recharged at around 3.4 volts. They must not be discharged below 3 volts or they will be damaged. They can be recharged at any time during the cycle as they have no 'memory' like the old Ni-Cads - and in fact it is advisable to recharge them before they reach full discharge, as this extends their service life. In theory they take 300 recharges but that is under ideal conditions - 150 is more likely to be achieved in practice. Don't fully discharge them - they will live longer.

    Li-ions do not have a good C-rating, for use in high-discharge current applications such as powering an e-cig atomizer. Also, like many products, batteries are often over-rated and the *actual* real-life rating is nearer 0.5C, not the 1C often given by the manufacturer. For example the typical real-life discharge rating of a RCR123 Li-ion rechargeable is about 500mA, half an amp, which as you can see is too low to power any kind of atomizer properly as they draw 1 amp and up. This is one reason batteries die - they are worked far too hard. These batteries are in effect not up to the job as they are too small. Physical size is important in a battery.

    Advantages of Li-ion batteries:
    - Very high charge density compared to Ni-Cad or Ni-Mh 1.2 volt cells ('main street' rechargeables).
    - Low self-discharge rate.
    - No memory effects.
    - Reasonable service life, about 150 - 200 recharges.
    - Cheapest from of lithium cell.

    - Poor high-current discharge performance.
    - Applications that require high current (like e-cigs) will shorten the life of the battery.
    - Unprotected batteries might be used by mistake, these are dangerous in high-current use mode, they can AND DO explode especially if used in series and then overdriven.
    - The protection electronics can fail due to being zapped by static, or a faulty charger - so the battery is rendered unsafe and there is no indication of this. It usually fails safe, i.e. dead - but this cannot be guaranteed.
    - These cells would be a poor choice for use in a mechmod with an RBA (a mechanical APV using a rebuildable atomiser system, where the coil resistance might be low either by design or accident) because the current draw would be too high for sufficient safety margin.

    All batteries of the type we are referring to - Li-ion, Li-Mn, Li-FePo4 - are actually Li-ion cells, but we just use the term 'Li-ion' to refer to the Li-Co type.

    Li-Mn or hybrid cells are intrinsically safer and in any case will deliver far more current for modern applications than protected Li-ion cells.

    IMR Li-Mn rechargeables
    Manufacturers include AW and BDL. AW are reported as higher quality. These batteries are unlikely to explode in use and there are no reports of this occurring (but they can melt down with flames if abused by for example short-circuiting or APV switch lock-on). They are recommended in place of Li-ions and do not need protection. These batteries are of high quality and are therefore expensive - but you get what you pay for.

    - No memory effect.
    - They have a high current discharge potential and therefore it may be wise to have a protection circuit in the main device. The discharge rating is often 8C, meaning it is likely that a lot of amps would be available if the battery were to be short-circuited (= a dead short or shorted-out).
    - They will be overcharged by old-technology chargers and may burst.
    - Overcharging (>4.25 volts) will shorten the service life, which is 500 charges under ideal conditions.
    - Discharging below 3 volts will shorten the service life.
    - If you run a Li-Mn down below the minimum discharge voltage, the cell can be damaged. As there is no 'trip out' as with a protected Li-ion, this is a concern.

    You can extend the service life of these cells by not recharging above 4.16 volts or discharging below 3.4 volts.

    Hybrid rechargeables
    These modern hybrid-technology cells combine Li-Mn with other battery technologies. They are a safer-chemistry type. We don't currently have enough history with them to fully detail their pros and cons.

    Advantages of hybrid cells:
    - They are a safer-chemistry type and need no protection
    - They can deliver high currents and have high C ratings
    - Quality is good because they come from the most respected names in battery technology
    - Some cells (check C rating as there is a wide variation) are a good choice for the toughest ecig applications (e.g. sub-ohm RBAs)

    Disadvantages of hybrids:
    - They are not a cheap battery
    - Because there are several different types, we don't know if all factors apply to all types
    - They will soon be counterfeited, like AW's cells, so make sure to buy from an authorised dealer
    - If you buy from Alibaba for example, to get a good deal, then don't be surprised if you get a counterfeit

    Li-FePo4 rechargeables
    These lithium ferrous phosphate batteries have a safer chemistry. Li-FePo4 is a newer technology and more expensive than Li-ion. This is a safe technology and they don't need any protection. AW batteries make these, and they are a very good choice as they are capable of taking the high load of an e-cig. They come in the same form-factor as the Li-ions used in ecig APVs and are an excellent substitute, preferable in all ways except for the cost - however, note the 2 cautions below.

    - Very long service life of 1,000 charges, under ideal conditions.
    - No memory effect.
    - Fast recharge.
    - Do not connect in parallel.
    - 2 cells max in series.
    - Discharge rate is commonly 5C to 8C, sometimes 10C, so they will certainly power atomizers effectively - but short-circuits need to be guarded against. The 26650 cell for example can put out 70 amps in a dead short.
    - Nominal voltage (type 1 eg RCR123 format) = 3.0 - 3.3v, min. discharge v = 2.8v, max. charge voltage = 3.6v; nominal voltage (type 2 eg AW 14500 Li-FePo4)= 3.6v.

    Special cautions:
    - Needs a special charger - different for the two types.
    - Some Li-FePo4 cells have a low discharge rate (C rating) of less than 1C - so it would be advisable to check the discharge rating before purchase.

    AW brand Li-FePo4 cells are reported as being the best.

    We have one report of a Li-FePo4 failure in an APV, but it might have been due to one of these two reasons:
    1. Tenergy Li-FePo4 cells are reported as being widely counterfeited. Because the batteries YOU are using could be counterfeits, it is VITAL that your APV has clearly visible safety features such as large gas vents. DOES IT?
    2. CAUTION: most Li-FePo4 batteries have a working voltage much lower than the Li-ion equivalent - 3.2 volts - and they CANNOT be used with Li-ion chargers.

    AW do make a 3.6 volt Li-FePo4 battery (their 14500 model) but this is not the norm for Li-FePo4. There is a very good chance that some users of Li-FePo4's will overcharge them, leading to failure, since the MAXIMUM charge voltage is 3.6 volts but the common Li-ion chargers put out 4.2 volts. Because of this, AW's Li-Mn rechargeables are thought to be the best option for APVs.

    NEVER place 3v batteries in a 3.7v (normal) charger. Li-FePo4's, with very few exceptions, are 3v batteries. These RCR123 format cells can be placed in series for a nominal 6 volts. Special precautions need to be taken with stacked batteries.

    Ni-Mh rechargeables
    These are the stock rechargeables found on main street. They come in the usual AA and AAA formats, with a nominal voltage of 1.5 volts although the real voltage is just 1.2 volts per cell - so 3 or 4 cells in series are needed for e-cigarette use. They are a safe technology and do not explode with mild abuse, and can be safely placed in series ('stacked'). No protection circuitry is needed. An APV can be built successfully using these standard rechargeables although it is worth pointing out that the C rating of most cells will be too low, leading in theory to shortening of service life.

    There are some minor disadvantages (shorter life etc) but on the whole they can be used successfully. Each cell delivers 1.2 volts, so some adjustment of the battery numbers / arrangements has to be made. For example 3 in series will provide 3.6 volts (good for normal e-cig use, with an on-load voltage probably around 3.3v), and 4 in series gives 4.8 volts (about 4.5 volts on load). These standard rechargeables are a good choice for APVs that are specifically built for the form factor and voltage requirements. It is likely that there will be noticeable voltage drop unless C-size cells are used; few 14500-size cells (= AA size) have enough C rating to run an atomizer.

    - Available everywhere.
    - The multi-cell battery holders found in electronics stores can easily be used as a boxmod case.
    - Safe technology, no explosions even when stacked.
    - In theory, a shorter service life. This does not seem to have been found to be the case in APV tests though, as many Li-ions don't last long in practice.
    - Lower voltage so more cells are needed - at least 3 cells in series, and 4 is better.

    Li-Poly rechargeables
    These lithium polymer battery packs are normally square/flat. Their use is not common in APVs. They are typically used in RC planes and cars. However more APVs are coming on the market with integral Li-Poly battery packs that cannot be changed by the consumer.

    We don't recommend the larger Li-Poly packs as they seem to be more delicate than other types and can apparently catch fire after impact damage such as being dropped, or while recharging after being dropped (see the battery fire videos linked below, which all involved Li-Poly packs). We are hoping that the smaller packs do not suffer from this issue.

    Tenergy Li-FePo4 batteries
    This is an interesting subject. Here are some of the factors:

    - Tenergy Li-FePo4 3 volt cells have a manufacturer's C rating of about 0.75.
    - If the manufacturer rates a cell at about 0.5 amps safe discharge, ECF cannot then tell people it is suitable for use at 2.5 amps. You can probably see why.
    - Independent tests seem to show, however, that these batteries are good quality and will perform at 4C with no problem. This would make them ideal for use as a stacked pair for 6v vaping.
    - However, and most importantly, it looks as if these could be the most counterfeited battery out there. In other words you may think you have a pair of Tenergy Li-FePo4 batteries but in fact you have a pair of junk reject re-covered unprotected Li-ion cells: the most dangerous situation possible.

    So, what is the answer? If you know for sure you have genuine Tenergy 3v Li-FePo4 batteries, it seems as if they could be very suitable (although we cannot officially say that for obvious reasons when the manufacturer says they cannot take more than a half-amp load). But you need to be very careful indeed because there is a chance the batteries might be fakes. That could leave you in a dangerous situation, if used stacked in a metal tubemod.

    SEE PART 2, in next post


    Members with specific technical knowledge are invited to help improve this page.

    Updated 2014-03-21 - page split into two parts; ICR recommendation demoted
    Updated 2014-03-20 - added IMR, ICR explanation; hybrid cell list reference
    Updated 2013-09-01 - added ref to Panasonic hybrid cells and Sony Spinel cells
    Updated 2012-04-24 - changed refs to APV from mods
    Updated 2012-04-15 - added advice to rest batteries after charging
    Updated 2012-03-10 - added latest info on Tenergy batteries
    Updated 2012-03-08
    Updated 2012-01-21
    Updated 2011-05-23

    • Informative Informative x 1
  2. rolygate

    rolygate Forum Manager Verified Member ECF Veteran

    Supporting member
    Sep 24, 2009
    ECF Towers

    Battery size chart - Li-ion rechargeables

    - most cells are 3.6 / 3.7v nominal (= same thing).
    - the first two digits of the battery code equals the diameter - so a 14500 is 14mm wide. The next two digits are the approx. length (ex: 50 = 50mm or 2 inches), and the last number is the shape, 0 = round.
    - CR123 is a size format - the proper code for rechargeables is RCR123a.
    - RCR123a batteries come in both 3.7 and 3 volt versions. CAREFUL!
    - NEVER place 3v batteries in a 3.7v (normal) charger. RCR123's are commonly 3v batteries (a nominal 3.2 or 3.3v cell is a 3 volt cell).
    - most sizes are available in Li-Mn and Li-FePo4.
    - small and medium Li-Mn's are 3.7v like Li-ion's. Large Li-Mn's *may* be 3.8v.
    - most Li-FePo4's are 3.2 / 3.3 volts. Be aware that single-battery devices will therefore have a lower voltage than normal.

    10180 battery - 3.7 volts nominal
    10mm x 18mm (1/3 AAA size)

    10280 battery - 3.7 volts
    10mm x 28mm (1/2 AAA size)

    10440 battery - 3.7v
    10mm x 44mm (AAA size)

    14250 battery - 3.7v
    14mm x 25mm (AA diameter but half length)

    14500 battery - 3.7v
    4.2 volts off charge, 3.7 volts in use, 3 volts minimum
    14mm x 50mm (AA size)
    THIS IS THE SMALLEST CELL THOUGHT TO BE SUITABLE FOR USE IN AN APV. Cells smaller than this simply do not have a high enough C rating. Not all cells of this size will have sufficient power, only AW Li-Mn cells are known to be safe at this size, others may be but this cannot be stated as fact.

    16340 battery - 3.7v
    16mm x 34mm (nominal CR123a size)

    17335 battery - 3 volt
    17mm x 35mm (close to nominal CR123a size but slightly larger so may not fit all equipment)

    17340 battery - 3 volt [may only be available in Li-FePo4]
    17mm x 34mm (close to nominal CR123a size but slightly larger so may not fit all equipment)

    17500 battery - 3.7v
    17mm x 50mm (slightly wider than CR-123, fits most flashlights, but 1.5 times the height of the typical CR-123a battery - two of these will often replace three CR-123a batts)

    17670 battery - 3.7 v
    17mm x 67mm (about the size of two CR-123 batteries, but less overall voltage, 4.2v max vs 6.6v max from two primary batteries)

    18500 battery - 3.7 v
    18mm x 50mm (wider than CR-123a, about 1.5 times the length of a single CR-123a battery)
    THIS IS THE SMALLEST SIZE WHERE THE CELL TYPE IS NOT IMPORTANT. All cells of this size and larger should be able to safely supply the 1.5 amps the average atomizer requires.

    18650 battery - 3.7v
    18mm x 65mm (wider than CR-123a, about 2x the height of a single CR-123 battery)

    26500 battery - (no Li-ion version* found in vendors lists, Li-Mn and Li-FePo4 are available)
    3.7 v - AW Li-Mn version
    3.2 v - Li-FePo4 version
    26mm x 50mm (this is "C" cell size)

    26650 battery - (no Li-ion version* found in vendors lists, Li-Mn and Li-FePo4 are available)
    3.7 v - AW Li-Mn version
    3.2 v - Li-FePo4 version
    26mm x 65mm (same diameter as C cell but slightly longer)

    * All these types of batteries are strictly speaking of the Li-ion type. To be accurate the statement should be: "No Li-Co version found.....".


    List of safe and less-safe batteries

    A good current listing (at 2014-03-21) of suitable batteries is here:
    (9) Battery Basics for Mods: IMR or Protected ICR? | E-Cigarette Forum

    Good batteries for APV applications have a C rating of greater than 6 amps / 6,000mA. In general:
    1. The biggest battery is the best battery in an APV
    2. The best manufacturers/vendors are AW, Panasonic, Sanyo, MNKE, Sony, Orbtronic (often using repackaged Panasonic cells).
    3. The best battery type, in order, is:
    a) Li-Mn (IMR)
    b) Hybrid
    c) Li-FePo4 - MUST BE THE HIGH-CURRENT TYPE - C rating of minimum 4C. Main use is for series circuits (stacking).
    d) Protected Li-ion

    Ni-Mh and Ni-Zn are excluded from this discussion as their voltage is so different that they cannot be used in standard APVs - however, if a device is built for them, they are suitable if they comply with the normal requirements (principally the C rating).


    Power rating for rechargeables

    The critical factor for ecig APV use is the C rating (discharge current) in amps. The minimum possible value for safe and effective ecig use is 2 amps (= 2,000mA) although ideally it needs to be higher as a regular atomizer usually draws 1.5A to 2.5A - high-current RBAs etc. will need a much better C rating than this.

    Chart of C ratings vs size
    1C or less for some Li-FePo4
    Assume 1C for generic Li-ion unless otherwise noted
    1.5C for ultra/sure/trust/-fire Li-ion
    2C for AW ICR (Li-ion)
    3C for BDL 10440 IMR (Li-Mn)
    5C for BDL 14500 IMR (Li-Mn)
    8C for AW 14500 and 16340 IMR (Li-Mn)
    10C for AW 18650 IMR (Li-Mn)
    10C for AW Li-FePo4

    Max drain rate in amps is C in mAh / 1000 x C rating
    Example: an AW IMR Li-Mn 14500 battery has a capacity of 600mAh. The C rating is 8C (it can supply a load of 8 times the capacity). Therefore the max discharge current in amps is:
    600 x 8 over 1000 (600 multiplied by 8 divided by 1000)
    = 4800 / 1000
    = 4.8 amps
    This shows it has enough beef to safely and effectively run an atomizer - which some 14500's don't. In other words it is less likely to go into thermal runaway if there is an internal fault in the battery, is overcharged, and is then used to power a device that draws a relatively high current such as an atomizer; and it will not suffer from excessive voltage drop when powering the atty.

    Useful formulas
    Amp draw = voltage / resistance
    Example: a 5 volt APV is used with a 2.5 ohm atomizer - what current is drawn?
    5 / 2.5 = 2
    The battery must supply 2 amps.

    Power used by atomizer in Watts = volts x amps, or volts x volts / resistance
    Example: a 5 volt APV delivers 2 amps to the 2.5 ohm atty - what power is used?
    5 x 2 = 10
    The atty uses 10 watts
    5 x 5 / 2.5 = 10 watts


    Hints and Tips

    If you want the best, safest battery for your APV, buy the largest AW IMR Li-Mn to suit, and get the best charger you can - a Pila charger for example, or Nitecore, Xtar.

    The safer APV is the one with the larger batteries. Small cells are heavily overworked running an atomizer. Don't forget safety features in the APV, either - see Links below.

    "If you want rechargeable CR123 batteries ONLY use protected or two Li-FePo4 (or Li-Mn if you can afford it - ed.) - BUT make sure that the Li-FePo4 is AW - it can take the load, some others can't. also sells a CR123 that can handle the load (16340 - just a different name)."
    - quote from a modder.

    "Personally I think vendors should warn against using anything except 18650 size batteries, the AW Li-Mn 14500, the AW Li-Mn 16340, or the AW Li-FePo4...... but I ain't holding my breath for the day that happens..."
    - quote from an experienced modder.

    When pairing batteries, especially in series (stacking them for double the voltage), it is important to use two identical batteries preferably of the same age.


    Size Chart - Pila Batteries

    Pila make high-quality rechargeable Li-ion cells, and are a good source of quality protected Li-ion cells if this is your choice.
    Left col: standard battery code, right col: Pila #

    18650 = 600A (was 168A)
    17650 / 70 = 600S (was 168S)
    18500 = 300A (was 150A)
    17500 = 300S (was 150S)


    Why do batteries explode?

    A while back this wasn't clear, but we are fairly sure about the answer now. There are several reasons but far and away the most likely is over-driving a battery that may be faulty in some way, followed by counterfeit batteries (which is basically the same thing). Here are the current answers in order of likelihood:

    1. Demanding too much current (in amps) from a battery that cannot safely provide it, and that may be faulty and that has been overcharged. Small rechargeable cells often do not have a discharge rating high enough to drive an atomizer safely. This means if there is some form of fault or issue anywhere in this series:

    manufacturing quality (low quality)
    manufacturing fault (any of a number of faults are possible)
    charging cycle (a charger can become faulty, and overcharge a battery)
    battery care (dropped or damaged, paired with a non-identical battery, etc)
    paired up in series (this magnifies the risk exponentially)

    ...batteries can fail and go into thermal runaway.

    Explosive events only happen when batteries are stacked and there are no safety features.

    Large batteries rarely suffer a violent de-gassing / explosion event; small cells are usually the culprits. The RCR123 format has more than its fair share of incidents, probably because it is normally under-rated for the job and paired in series with another battery. Very few RCR123 types are rated high enough to run an atomizer safely. 'Safely' means that if there is a fault somewhere (as in the 'chain' list above), the cell can still work without danger.

    There is no safety margin in most of these small cells. If you get the biggest battery you can, the safety factor is massively increased - many (possibly most) small cells can't realistically handle the load of an atomizer.

    2. Counterfeit batteries are a big problem now - and this will get worse. In practice, you cannot know what your batteries really are: just because the label says Brand X does not mean that is what they are.

    Counterfeiters buy cheap reject unprotected Li-ion batteries, strip the cover off, and fix a fake label on them. You think you have good Li-FePo4 batteries but in reality they are junk unprotected Li-ion cells. This is a fast track to a meltdown, or even an explosion if they are stacked and there are other issues.

    3. Placing them in series to double the voltage increases the risk. There are more factors that can go wrong, such as double the chance one cell in the pair might be faulty; pairing two cells that are not absolutely equal in all respects; and doubling the voltage and thus the workload.

    4. Using unprotected lithium batteries is a fast track to danger. Just don't do it.

    Use protected lithium (Li-ion) rechargeables, or much better, a battery with a safer chemistry such as Li-Mn or hybrid. We have not heard of an Li-Mn cell failing explosively, although it may happen of course - no rechargeable battery is entirely safe. We only have one report of a Li-FePo4 failing (and it was probably a counterfeit). There are dozens of reports of Li-ion cells failing violently.

    5. System faults may be an issue - such as a faulty switch, or a metal edge that scrapes off some of the battery coating, allowing a different negative path to exist (a 'short' to the case).

    Take a look at the videos of the lithium battery fire in the Links section below, and you will appreciate the possibilities better. The battery that caused the expensive blaze in the auto workshop was of a different type to those we use - a Li-Poly flatpack cell - but some of the chemistry is similar.


    Are APVs safe?

    It depends what you mean. From the above factors we can see that the safest battery is the biggest 'safer-chemistry' cell you can buy. This is why a 26650 cell is intrinsically safer than an 18650 cell for ultra high load duty.

    You also need the right charger for it. The APV itself needs to have some safety features such as large gas vents.

    No lithium batteries are absolutely safe, and therefore no APV can be said to be absolutely safe - but you can cut the risk to very low levels by taking the sensible route. There is more risk than with a standard e-cigarette because the cells used in APVs are big enough to cause more problems if they fail; and because standard e-cigs are safe due to several factors such as built-in protection.

    Let's look at two risk cases:

    Case #1
    If you: buy a (1) large (2) AW IMR Li-Mn battery (18650 and above) and (3) buy the correct charger, and (4) run it in single-cell mode, and (5) test the cell and the charger for correct voltage, and (6) the APV the battery is used in has large gas vents - then it seems unlikely you will ever experience a serious incident.

    As soon as you vary any of those 6 factors, the risk increases.

    Case #2
    If you use two small unprotected Li-ion cells in series, in a metal tubemod with little or no gas venting, with a cheap charger, and never test the voltages - then you're probably at maximum risk.

    Let's say that Case #2 has a risk factor of 99 as the only thing you can do worse is charge and then immediately use two primary cells; and in Case 1, you're at factor 10 ex 100 - the lowest practicable risk rating. Everything else is somewhere on that scale. You decide, by your purchase and usage decisions, where you will be on the scale.

    No APV is entirely safe, it can't be, due to the batteries inside it, which are all potentially miniature sticks of dynamite due to their stored energy. Watch the lithium battery fire vids and you will understand this.

    If an APV has no safety features built in, the risk factor goes up. For example if it has no gas vent holes, the casing may have to fail somehow to vent the gases, and this is going to be more violent. A small RCR123 cell has the potential to cause a surprisingly powerful explosion if contained in a strong, gas-proof container. No normal container is strong enough to hold an explosion in - the opposite is true: the stronger the container, the more powerful the explosion. A grenade is just a strong gas-proof metal casing. Metal tube APVs need especial care in your purchase decision: buy one with gas vents.

    You need to take every possible action to ensure that your APV is not a potential pipe bomb. Each of your purchase decisions has a crucial effect on this:-

    1. Could you buy an APV with a larger battery? Larger batteries are safer.
    2. Did you buy a genuine AW Li-Mn battery from an authorized distributor - or something cheaper? There are no cheap AW batteries - a cheap AW cell is a counterfeit.
    3. Did you get the best battery charger you could find - or the cheapest?
    4. Do you have a multimeter, so that you can test the charge voltage and resting voltage occasionally?
    5. Does your APV have built-in safety features such as large gas vents?
    6. If it is a metal tubemod (the type with a history of explosions when using two batteries in series), does it have very large gas vents?
    7. If you are using two cells in series, are there multiple safety features?

    In effect, you decide the scale of risk. Every decision you make either reduces or increases the risk. Don't try to offload the risk onto someone else - IT'S ALL YOURS AND ONLY YOURS.

    APVs with metal casings
    Is a device with a metal casing safer or less safe than one with a fragile/plastic casing?

    This question cannot be answered as it would require extensive destruction testing of several types, in order to provide an answer. It is true that small gas vent holes are not sufficient to prevent an explosion, but it should be carefully noted that there are several reports of events where an explosion occurred, stating that gas vented strongly for several seconds before the explosion - indicating that small vents may at least give a warning of the event, enabling the device to be dropped.

    It seems logical, though, that in the case of a metal tubemod, it should have large gas vents. The prospect of the top cap blowing off first is not pleasant, and where this happened, serious injury has resulted. DON'T USE A METAL TUBE APV WITH TWO BATTERIES AND NO LARGE GAS VENTS unless it is a fully-electronic device.

    At 2012-01-18 there has just been a serious explosive event where the 2-battery metal tubemod's top end blew off, causing serious facial injuries and putting the victim in intensive care.
    2012-02-16: another exploding APV incident of a very similar kind, with reports of the top end blowing off causing serious injury (this one was reported around the world).




    Useful info, good list of safer-chemistry cells:
    (9) Battery Basics for Mods: IMR or Protected ICR? | E-Cigarette Forum

    A useful small article on different rechargeable types:

    A useful battery listing:
    Batteries + carriers & testers

    AW batteries - info & direct sales:
    AW's LiIon Batteries Sales Thread *Part 12*

    Micro USB Li-ion chargers:
    FS: Worlds smallest Li-ion charger with led display! -dual ma versions now available!

    Video footage of a Li-ion battery explosion :
    Li-poly battery fire footage | E-Cigarette Forum

    In the field of small rechargeable battery-powered equipment, flashlight/torch users have done much work. There are many useful pages on the flashlight users' sites. Here is an example, an analysis of micro LED flashlights and batteries to a very high standard:
    A look at small flashlights

    Link to the poisoning incident from a Li-ion batt explosion, candlepower forum, post [HASHTAG]#128[/HASHTAG]:
    ROAR of the Pelican (CR123 Explosion during use, firsthand account)

    Another poisoning incident - links in last post:
    Inhaled vapors from battery!!!


    APV safety features:
    EMSS - ECF Metal tubemods Safety Specification


    Battery charging issues

    ~ In any rechargeable battery system, the charger is at least as important as the battery. ~

    One reason batteries die is that they are not charged fully and/or correctly. If we look at car batteries for example, the only reason most die is because they are not charged correctly, since this is impossible with a standard car alternator - it provides a fixed voltage of 13.2 volts (the 'float voltage') and varies the current, not the voltage. A lead-acid battery cannot be charged fully with one voltage, it needs a minimum of two voltages and ideally three voltages for full service life:
    - A 'bulk charge' value of 14.4 volts at high current for short time intervals.
    - A 'float' voltage of 13.2 for long periods.
    - An 'equalisation' voltage of 17.5 volts at very low current, occasionally, in order to knock sulphate off the plates.

    This can only be achieved by using an alternator controller with programmed voltages. If such a controller is used, and battery electrolyte levels checked, a car battery might last 100 years. It's true that over-discharging them below their minimum voltage is another main cause of battery failure - but this is unlikely in a car battery unless the vehicle is left unused. Another way to kill a battery is to over-current discharge it, that is, ask it to supply more current than it is physically capable of safely doing, in its normal working profile. For a car battery this would be several hundred amps though - they can supply 5,000 amps in a short-circuit. The poor charging regime is what kills car batteries, as they are never charged more than 70% by the fixed 13.2v a car alternator outputs.

    So you can see that the charger is critical. You get what you pay for. Buy the best charger you can find, it's worth it. The best car battery chargers are called Marine Chargers (from a yacht chandler), these have programmed voltages since boat owners cannot afford dead batteries, there's no roadside assistance out there to save their bacon if they start drifting onto the rocks. Specialist marine alternators and truck alternators do the same job.

    So: you might go out and buy the cheapest battery charger you can get; then you'll put your APV in front of your face, and ask the battery/batteries to deliver more current than they are happy to deliver (if standard Li-ion rechargeables below 18650 size). Is that wise?

    These chargers will charge AW and Pila batteries, Li-Mn and Li-ion.
    They will not charge most Li-FePo4's.
    Battery spacers may be needed to charge all sizes of battery.
    Pila IBC Lithium Charger (With extra free spacers)


    Members with specific technical knowledge are invited to help improve this page.


    Update history

    2014-03-21 Major update, page split into two

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