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As you all know, there have been a spate of battery explosions over the past few weeks involving lithium and lithium ion batteries. This isn't anything new (remember the laptop battery fires?), but as lithium batteries become more common amongst the laser community, safety is one of the most overlooked issues with them.
There are two types of lithium batteries- lithium primaries (which contain lithium metal) and lithium ion rechargables (which only contain lithium compounds). Both are extremely dangerous if used incorrectly.
In Lithium primary cells, the lithium metal is expended as the cell is depleted, whereas with lithium ion rechargables the compounds remain, albeit in a lower-energy state.
Lithium ion batteries are rechargable, however, lithium primaries are NOT. Attempting to charge lithium primaries may result in a fire and/or explosion.
Charging and storage
Lithium ion batteries should never be charged unsupervised, regardless of whether they are protected cells or not. Check the cells every hour (at the very leas), and quickly unplug the charger if they are too hot to touch. Move these cells outside in an area away from flammable materials, and allow them to cool. It is inadvisable and dangerous to use overheated cells.
Charge the cells in a metal box, preferably along the lines of a large ammunition box. Do NOT use a completely sealed box, as that will only turn the box into a fragmentation grenade when a battery does explode. The box will also contain any lithium metal in case of a leak or fire.
Before storing batteries, ensure that they are not shorted out by any objects, including other batteries. It is advised to use plastic battery cases to store batteries in.
Extinguishing Lithium Fires
So, you've taken all the correct precautions when charging, but a battery burst. What happens now?
Firstly, remember the days of High School chemistry class? Lithium is an alkali metal- and as a result it's very reactive. Once a lithium fire starts, it's incredibly hard to put out.
The WORST thing you can do is to throw water on it. Lithium will react with the water to produce hydrogen gas, which will only intensify the fire.
The other problem is that most household extinguishing agents don't do terribly much for a lithium fire either. Being a Class D fire (combustible metal), most extinguishing agents will react in an adverse way to it (e.g. water and foam), or will not work at all. (e.g. dry chemical*)
*There is a difference between dry chemical and dry powder. The terms are not interchangeable.
Metal fires will often burn hot enough to be able to strip the oxygen from CO2 and continue burning. They will also break down Halon and related agents into hydrogen chloride into other toxic compounds. Sodium Bicarbonate (Class BC dry chemical) and ammonium monophosphate (class ABC dry chemical) extingushers have little to no effect.
In the heat of a fire the chemicals in lithium ion batteries may also decompose to form lithium metal. This lithium metal combusts more violently than lithium compounds, and also releases dense lithum oxide smoke, which is an irritant.
Extinguishing these fires isn't an easy task. Better not let the fire start in he first place- however, sometimes accidents do happen. Short of investing in a (very expensive) Class D dry powder extinguisher, there's not much common fire extinguishers can do.
When fires do happen, you've got two options- dry sand, or dry table salt. Both work equally well in large amounts. You will need at least two kilos, with 3 or 4 if you have lots of batteries stored together.
Note the emphasis on the word dry. The extinguishing agent must be kept in an enclosed container, free from all moisture before use. Any water, even miniscule amounts, will react with the lithium and intensify the fire. One of the best options is to store it in one of those larger cookie jars with the rubber seal on the lid. Do not expose the extinguishing agent to the atmosphere.
If possible, tape a bag of silica gel dessicant to the lid of the jar. This will help to keep the agent dry.
Store a long-handled metal spade or ladle near the jar. Using your hands, or the jar itself, is a very bad idea. Keep the spade with the jar at all times.
Applying the extinguishing agent is easy- simply scoop the stuff from the jar, and cover the burning lithium fragments with it completely. Do not leave any parts of the burning material exposed to air. Continue to pile the sand or salt over the material until it is covered with at least two centimeters of sand or salt.
If possible, cut power to the charger (if the battery is still in the charger) before extinguishing. If this is not possible, then apply the extinguishant first.
Remember- common sense applies here. In an explosion, flammable material will be sprayed all over the room. Put out the material near flammable materials first (near wood, paper or clothes).
The sand works because it cuts off the oxygen supply to the fire, and quickly draws heat away from the fire. (removing two elements from the fire tetrahedron)
The salt works because it melts, and forms a thin, molten blanket over the material, cutting off oxygen supply to the burning metal. Salt also cools the burning metal, but not as well as sand or copper powder (found in Class D extinguishers).
So, that's it. There's not much needed, but basic safety precautions (jar of sand/ salt, and a spatula) can easily save you from $$$ worth in property damage.
The jar isn't any different from a proper Class D extinguisher (save for the fact you have to scoop it on yourself). They either use salt or copper powder as an extinguishing agent, and it works.
A quick dot-point summary of everything above, by charliebruce. Nice, short points that are easy to remember:
Whilst storing:
* Store in a strong box (ammo case?)
* Avoid short-circuiting them
* Remember that pressure is a problem as well as the shrapnel produced - a completely sealed box is not ideal.
Whilst using:
* Never mix charged and part-charged cells, or disposable and rechargable cells.
* If they get more than mildly warm then stop using them and consider replacing - if they ever get too hot to touch when charging or discharging, then dispose of them.
* Never use any cells you aren't confident are safe, especially in high-current appliances (torches, high powered lasers etc) - you can see the results of torch explosions elsewhere and it isn't pretty.
Whilst charging:
* Make sure they are rechargeable types!
* Never leave them unattended, especially in the first section of charge cycle.
* Charge in a safe container (similar to the one for storage) but keep your "storage" and "charging" boxes separate - if your charging batteries have a problem, you don't want them near the other cells!
* If they get uncomfortably hot (greater than body temp.) at any point, especially in the first hour of charging, then stop charging them for a while. If they get very hot indeed, stop charging them and when cool, dispose of (recycle) safely.
* Always have an appropriate extinguisher nearby (DRY Salt or sand).
In the event of fire:
* Cut power to the charger/device first.
* Never use water or CO2 - only DRY sand or salt.
There are two types of lithium batteries- lithium primaries (which contain lithium metal) and lithium ion rechargables (which only contain lithium compounds). Both are extremely dangerous if used incorrectly.
In Lithium primary cells, the lithium metal is expended as the cell is depleted, whereas with lithium ion rechargables the compounds remain, albeit in a lower-energy state.
Lithium ion batteries are rechargable, however, lithium primaries are NOT. Attempting to charge lithium primaries may result in a fire and/or explosion.
Charging and storage
Lithium ion batteries should never be charged unsupervised, regardless of whether they are protected cells or not. Check the cells every hour (at the very leas), and quickly unplug the charger if they are too hot to touch. Move these cells outside in an area away from flammable materials, and allow them to cool. It is inadvisable and dangerous to use overheated cells.
Charge the cells in a metal box, preferably along the lines of a large ammunition box. Do NOT use a completely sealed box, as that will only turn the box into a fragmentation grenade when a battery does explode. The box will also contain any lithium metal in case of a leak or fire.
Before storing batteries, ensure that they are not shorted out by any objects, including other batteries. It is advised to use plastic battery cases to store batteries in.
Extinguishing Lithium Fires
So, you've taken all the correct precautions when charging, but a battery burst. What happens now?
Firstly, remember the days of High School chemistry class? Lithium is an alkali metal- and as a result it's very reactive. Once a lithium fire starts, it's incredibly hard to put out.
The WORST thing you can do is to throw water on it. Lithium will react with the water to produce hydrogen gas, which will only intensify the fire.
The other problem is that most household extinguishing agents don't do terribly much for a lithium fire either. Being a Class D fire (combustible metal), most extinguishing agents will react in an adverse way to it (e.g. water and foam), or will not work at all. (e.g. dry chemical*)
*There is a difference between dry chemical and dry powder. The terms are not interchangeable.
Metal fires will often burn hot enough to be able to strip the oxygen from CO2 and continue burning. They will also break down Halon and related agents into hydrogen chloride into other toxic compounds. Sodium Bicarbonate (Class BC dry chemical) and ammonium monophosphate (class ABC dry chemical) extingushers have little to no effect.
In the heat of a fire the chemicals in lithium ion batteries may also decompose to form lithium metal. This lithium metal combusts more violently than lithium compounds, and also releases dense lithum oxide smoke, which is an irritant.
Extinguishing these fires isn't an easy task. Better not let the fire start in he first place- however, sometimes accidents do happen. Short of investing in a (very expensive) Class D dry powder extinguisher, there's not much common fire extinguishers can do.
When fires do happen, you've got two options- dry sand, or dry table salt. Both work equally well in large amounts. You will need at least two kilos, with 3 or 4 if you have lots of batteries stored together.
Note the emphasis on the word dry. The extinguishing agent must be kept in an enclosed container, free from all moisture before use. Any water, even miniscule amounts, will react with the lithium and intensify the fire. One of the best options is to store it in one of those larger cookie jars with the rubber seal on the lid. Do not expose the extinguishing agent to the atmosphere.
If possible, tape a bag of silica gel dessicant to the lid of the jar. This will help to keep the agent dry.
Store a long-handled metal spade or ladle near the jar. Using your hands, or the jar itself, is a very bad idea. Keep the spade with the jar at all times.
Applying the extinguishing agent is easy- simply scoop the stuff from the jar, and cover the burning lithium fragments with it completely. Do not leave any parts of the burning material exposed to air. Continue to pile the sand or salt over the material until it is covered with at least two centimeters of sand or salt.
If possible, cut power to the charger (if the battery is still in the charger) before extinguishing. If this is not possible, then apply the extinguishant first.
Remember- common sense applies here. In an explosion, flammable material will be sprayed all over the room. Put out the material near flammable materials first (near wood, paper or clothes).
The sand works because it cuts off the oxygen supply to the fire, and quickly draws heat away from the fire. (removing two elements from the fire tetrahedron)
The salt works because it melts, and forms a thin, molten blanket over the material, cutting off oxygen supply to the burning metal. Salt also cools the burning metal, but not as well as sand or copper powder (found in Class D extinguishers).
So, that's it. There's not much needed, but basic safety precautions (jar of sand/ salt, and a spatula) can easily save you from $$$ worth in property damage.
The jar isn't any different from a proper Class D extinguisher (save for the fact you have to scoop it on yourself). They either use salt or copper powder as an extinguishing agent, and it works.
A quick dot-point summary of everything above, by charliebruce. Nice, short points that are easy to remember:
Whilst storing:
* Store in a strong box (ammo case?)
* Avoid short-circuiting them
* Remember that pressure is a problem as well as the shrapnel produced - a completely sealed box is not ideal.
Whilst using:
* Never mix charged and part-charged cells, or disposable and rechargable cells.
* If they get more than mildly warm then stop using them and consider replacing - if they ever get too hot to touch when charging or discharging, then dispose of them.
* Never use any cells you aren't confident are safe, especially in high-current appliances (torches, high powered lasers etc) - you can see the results of torch explosions elsewhere and it isn't pretty.
Whilst charging:
* Make sure they are rechargeable types!
* Never leave them unattended, especially in the first section of charge cycle.
* Charge in a safe container (similar to the one for storage) but keep your "storage" and "charging" boxes separate - if your charging batteries have a problem, you don't want them near the other cells!
* If they get uncomfortably hot (greater than body temp.) at any point, especially in the first hour of charging, then stop charging them for a while. If they get very hot indeed, stop charging them and when cool, dispose of (recycle) safely.
* Always have an appropriate extinguisher nearby (DRY Salt or sand).
In the event of fire:
* Cut power to the charger/device first.
* Never use water or CO2 - only DRY sand or salt.
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