• A PBusardo Video - A Visit To The Yongdeli Battery Factory

    2017.10.15 0 Posted By Cool

    2016-03-23

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  • Mech Mode Safety Resistance Chart

    2017.10.14 0 Posted By Cool

     

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  • Why bother with testing cell temperature?

    2017.10.13 0 Posted By Cool

    Source: e-cigarette-forum.com - Published by Mooch in the blog Mooch's blog.

     

    As an example, suppose one cell had a 30A continuous discharge rating (CDR) and another cell had a CDR of 20A. The 30A cell sounds like it would be a better choice for use in a device that draws lots of current. But if it rises to a temperature of 120°C delivering that current, that cell is overrated and will have a very short life...if it doesn't vent or burst first. The 20A cell might actually be a better choice depending on how hot it gets. Something you could determine if you had the temperature data.

    I feel strongly that temperature must be a part of any cell testing or otherwise the tests can't be used to compare cells. These tests are my first step in trying to get a handle on how we can give these cells true CDR's. Based not only on capacity and voltage-under-load but also based on how safe they are to use at different discharge current levels.

    Manufacturers rate their cells for use at temperatures up to 60°C, maximum. At temperatures exceeding about 45°C a cell's aging accelerates, shortening its life. At 70°C-80°C a cell starts increasing its self-heating due to additional exothermic chemical reactions. If this self-heating is not stopped, or the heat pulled away by cooling, it will eventually lead to venting, bursting, and possibly thermal runaway. At approximately 120°C an important component in a cell starts melting (the separator), leading to short-circuiting and more self-heating. This is a point where the cell starts to be in big, big trouble. And so is anyone using that cell.

    Different chemistries have different temperature thresholds for thermal runaway but all suffer similarly at temperatures below this (accelerated aging, exothermic reactions creating gas and increased internal pressure, separator melting, etc) which can lead to venting and/or bursting. It's why I did not differentiate between the chemistries when setting the maximum temperature I would let a cell reach before stopping a test.

    Testing ICR cells (LiCoO2, "lithium-cobalt-oxide", "LCO") is riskier than testing the IMR (LiMn2O4, "lithium-manganese-oxide", "LMO") cells we normally recommend for use in a vaping device. This is due to the lower thermal runaway temperature of lithium-cobalt. It makes measuring of the cell temperature during a discharge all the more important.

    I have set a safety limit of 100°C for all of my tests, which is a ridiculously high temperature to operate a cell at! But I know that vapers will always want to reduce device size by reducing the number of cells so we'll go as hot as we can without getting too close to thermal runaway. Know that operating at over about 45°C reduces cell life though. If the cell exceeds 100°C before completing a discharge at its continuous discharge rating (CDR), then the cell is definitely overrated. It's just to dangerous to use continuously at that discharge current level. Under certain circumstances I'll let the discharge continue even if the cell temperature is above 100°C. But this is guaranteed to damage the cell and might lead to venting or thermal runaway.

    For reasonable cell life, I have set a limit of 75°C. While this is high enough to speed up the aging of the cell, it will still allow using the cell for a reasonable amount of time before needing to replace it. Beware of using any cell at higher temperatures than this. Not only can the damage become quite severe very quickly but it also takes you closer to the temperature at which the cell could vent.

    I realize that vaping does not discharge the cell continuously and that it will run cooler when used in a device, even if each time the device is fired it draws current equal to the cell's CDR. But we must have a safety margin when using these cells! If a device autofires then knowing that the cell you have picked will not vent, or worse, is very important. And a cell that is short-circuited might not destroy itself, and your device, if we can pick the one that runs cooler at high discharge current levels. This can only be done if we know how hot these cells get.

    I would love to see the ECF community come together to create a set of standardized test requirements to use when comparing cells and determining their safety at different discharge current levels. Using these tests we could set an accurate and safe current limit for each cell. Not just for continuous current, but also for "pulse" current testing that better simulates what happens when cells are actually used in a device. Additional tests could include cell leakage rate (good for estimating degree of damage to a cell), internal resistance, total joules delivered for each discharge current level (not a test, just some math), and cycle life testing.

     

     

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  • Mooch´s 18650 Battery Safety Ratings - 10/2/2017

    2017.10.13 0 Posted By Cool

     

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  • Mooch´s Recommended Batteries - 3/25/2017

    2017.10.13 0 Posted By Cool

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  • Mooch´s Battery Charge Current Ratings : 8/28/2017

    2017.10.13 0 Posted By Cool

     

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  • How can we extend the life of our batteries?

    2017.10.13 0 Posted By Cool

    Source: e-cigarette-forum.com - Published by Mooch in the blog Mooch's blog.

     

    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.

    Temperature

    • 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.


    Discharging

    • 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.


    Charging

    • 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.


    Miscellaneous

    • 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.


    Additional Information

    ***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.

     

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