are lithium ion battery really that dangerous?

firebolt126

Newly Enlightened
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Mar 11, 2014
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Before I came to this forum, I always thought lithium ion battery were fairly safe. I remember sticking any old rechargeable AA battery into my old charger my dad had from his old company (that charger is probably 10+ years now). We leave them unattended for hours and pop them out once its done. My friends also does the same thing, especially those that use power tools and had bigger lithium ion rechargeable batteries. They would occasionally leave their 12-18.5v lithium ion battery for their drills charging unattended while they do something else. Are 18650 battery so prune to dangerous situation that ones must be cautious of overcharge and over discharge? What about those cell phones and laptop people leave charging overnight. I believe that kill the battery life when overcharging occur, but I believe the electronics are built in with very capable technology to prevent accidents.
 

oKtosiTe

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Jan 7, 2012
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Sweden
Before I came to this forum, I always thought lithium ion battery were fairly safe. I remember sticking any old rechargeable AA battery into my old charger my dad had from his old company (that charger is probably 10+ years now). We leave them unattended for hours and pop them out once its done.
AA cells are not Li-ions. When they are, they're generally referred to as (Li-ion) 14500 cells.
While leaving AA cells in a decent smart charger after charging is done, many dumb chargers will simply continue to overcharge fully charged cells, often resulting in :hot: electronics and batteries.
Good practices, good cells and good chargers make Li-ions very safe for daily use, but overcharging or overdischarging low-quality/unprotected cells and using them in series inside a aluminum pipe-bomb (read "flashlight") is a recipe for disaster. I regularly link to this thread as an example.

My friends also does the same thing, especially those that use power tools and had bigger lithium ion rechargeable batteries. They would occasionally leave their 12-18.5v lithium ion battery for their drills charging unattended while they do something else. Are 18650 battery so prune to dangerous situation that ones must be cautious of overcharge and over discharge? What about those cell phones and laptop people leave charging overnight. I believe that kill the battery life when overcharging occur, but I believe the electronics are built in with very capable technology to prevent accidents.
Power tools, laptops, phones, etc usually have protection and balancing circuitry built-in. Since it is easy to buy cheap and/or unprotected cells (of suspicious quality), it is better to be safe than sorry and warn prospective users of the risks.
Many older and cheaper tools actually use different chemistries altogether.

Oh, and since this is one of your first three posts: :welcome:
 
Last edited:

SilverFox

Flashaholic
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Jan 19, 2003
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Bellingham WA
Hello Firebolt126,

Welcome to CPF.

Let me give you two different scenarios and see if you can pick the one that could be more dangerous...

First of all you need to realize that stored energy can be dangerous. NiMh and NiCd cells have about 1/3 the stored energy as Li-Ion, so there is a higher potential for danger when using Li-Ion.

Scenario 1: You purchase a brand name laptop computer. The computer runs on a Li-Ion battery pack, has a sophisticated charging algorithm built in, has protection against high and low voltages, and has thermal protection. The circuit that runs the laptop has been designed, tested, and approved for its intended use. The cells used are designed around the intended use paying attention to use rate, charging rate, and run time.

Scenario 2: Your laptop battery wears out and you hear that you can take it apart and there is a good chance that some of the cells may still have some life left in them. You harvest the cells from the battery pack removing all the extra circuitry and plan on using those. Since you paid nothing for the cells, you aren't interested in paying for a quality charger so you go for the cheapest charger you can find. You also don't take the time to test how well the cells perform under your intended use and also don't bother to check the charger to see if it is working properly. Since your "barn burner" light only uses 3 cells and the laptop battery pack had 6 cells you figure you are reducing your risk in half.

As you can see in their intended application batteries can be safe but when you change everything without the proper engineering and testing things can go wrong.

Most lights don't have the circuitry that laptops and cell phones have. This means that there is more opportunity for things to go wrong. The R/C people started replacing Nickel based batteries with Li-Po batteries before we started using them in flashlights. We decided that warnings could be helpful after reading and watching reports of houses, garages, and automobiles being burned up after not paying attention to the details involved with dealing with Li-Ion chemistry.

If you find a light that is powered off of your power tool battery and you charge the battery with the charger provided for the power tool, you have most likely minimized any danger.

As a result of this attitude of caution we have people running tests on various brands of cells and various chargers and pointing out the positive and negative aspects of them. In addition people that are modifying and making flashlights are paying attention to the particular requirements of Li-Ion cells. We are getting closer to much safer use.

A little common sense goes a long way when dealing with this chemistry, but don't discount the dangers and once you understand them you should do fine.

Tom
 
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