Recharging drone battery burns down (ahem!) a Fire Station
- Thread starter KurtpH
- Start date
@maelstrom - I expect they may cause an increase in battery temperature due to the containment but the Bat-Safe has metal walls that I imagine would conduct some of that away, and as long as the battery is reasonably healthy would withstand the amount of heat generated without causing runaway. If a battery is that close to having thermal runaway it should be showing signs of its condition, which should be an indicator either not to charge it or to watch it closely.
@cgmaxed - From the photos, I'd say the charging was taking place inside the centre vehicle. I'm guessing that there was no smoke detector inside the vehicle and the way those things burn, a significant amount of damage may have already been done by the time it was detectable, especially if one faulty battery then set others alight.... I couldn't see any fire suppression systems in the garage itself in the photos of the wreckage.
@cgmaxed - From the photos, I'd say the charging was taking place inside the centre vehicle. I'm guessing that there was no smoke detector inside the vehicle and the way those things burn, a significant amount of damage may have already been done by the time it was detectable, especially if one faulty battery then set others alight.... I couldn't see any fire suppression systems in the garage itself in the photos of the wreckage.
cgmaxed
Well-Known Member
I didn't look at the article. I didn't realize it started in a vehicle. My comment can be disregarded.
I was charging a 6S 1500 Mah battery when this happened. Glad I was using the Bat Safe. A lipo bag (I have several) would not have contained this.
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cgmaxed
Well-Known Member
I was thinking, I bet a fire safe would be a good place to put a charging lipo. Even with the lid open, a hard firesafe would contain the fire pretty well, unless sparks and hot pieces started flying out of the safe. Keeping the lid shut would definitely keep the fire contained, until it burned itself out.
Thing is that charging batteries creates heat. Anything that stores that heat (bag/box/tight shorts) is going to cause other problems. Smart charges and battery controllers will reduce charge rate when the battery heats, but cheap off-brand chargers probably won't have the safety features, compounding the problem.
In any case, if a device starts burning, creates it's own oxygen in the process, and is inside a sealed case, you now have what is commonly referred to as a bomb.
A fire safe - one of the self sealing types - would probably be a good option. Or, a glass firing kiln - if fusing glass is your hobby. Safes start at rating around for 1000f. Sentry safes are rated 1700f for an hour, and are fairly cheap, and small. Kilns are rated to 2450f for days, but are expensive (relative to a safe). But hey - with a kiln now you can make glass and ceramic accessories and bling up your Drone!
In any case, if a device starts burning, creates it's own oxygen in the process, and is inside a sealed case, you now have what is commonly referred to as a bomb.
A fire safe - one of the self sealing types - would probably be a good option. Or, a glass firing kiln - if fusing glass is your hobby. Safes start at rating around for 1000f. Sentry safes are rated 1700f for an hour, and are fairly cheap, and small. Kilns are rated to 2450f for days, but are expensive (relative to a safe). But hey - with a kiln now you can make glass and ceramic accessories and bling up your Drone!
@cgmaxed - I don't believe your earlier comment should be disregarded - it is relevant in that there should have been a dedicated area set aside for charging with adequate detection (and given it was a Fire Station, some form of suppression?) available in that area.
Also, I think an unmodified fire safe would in all likelihood be a bad idea - don't forget, they are designed to protect the contents from a fire outside the safe... A fire inside the safe, particularly if sealed, would create a significant amount of pressure, that's also why Ammo cans are no good unless they're modified to vent the gases safely in the event of a fire. If the lid/door is left open or ajar, hot, toxic gases are not effectively filtered they could also transfer a lot of heat, and possibly embers which may trigger a fire in nearby materials.
If anyone is interested, you can see what I built here:
I'm not saying these are by any means the best option but may inspire people to come up with something even better 
Also, I think an unmodified fire safe would in all likelihood be a bad idea - don't forget, they are designed to protect the contents from a fire outside the safe... A fire inside the safe, particularly if sealed, would create a significant amount of pressure, that's also why Ammo cans are no good unless they're modified to vent the gases safely in the event of a fire. If the lid/door is left open or ajar, hot, toxic gases are not effectively filtered they could also transfer a lot of heat, and possibly embers which may trigger a fire in nearby materials.
If anyone is interested, you can see what I built here:
Thanks eEridani,
The pressure is taken care of by vent holes with a layer of glass fibre matting for filtering, it's further retained by metal mesh screens to keep glass fibres from falling out - it allows gas pressure to escape while filtering combustion particles and trapping a lot of the heat, unfortunately the toxic components to the gas will still be released so good ventilation is still needed, but that would be the case anyway - even the Bat-Safe says it doesn't filter out all the toxins in the gas. I assume they're using plain glass fibre matting but I haven't seen any specific info on that. Here's the reply from their website FAQ regarding a user question about the toxic fumes -
FAQ | BAT SAFE LLC | United States
Frequently asked questions about our BAT SAFE's.
www.bat-safe.com
If they ever develop a matting that has catalytic or other properties for neutralising the toxins in the gas, it's an easy enough move in my build to replace the glass fibre matting (you'd need to separate the lid components in the Bat Safe)... thankfully I haven't had my build tested yet and I hope that remains the case!!
One other method I have seen is to use cinder blocks to encase an area used for charging and cover with a plastic bag filled with sand. In the event of a fire it burns through the bag and the sand envelopes the fire. It won't put it out completely but effectively contains it until the Lipo burns out. I have also decanted some sand into small buckets with lids for field use - in the event of a lipo fire in the field, at least I have something relatively cheap, readily available and and effective on hand to cover the fire with. Again, hoping I never need it!
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Wow -- a company suggesting they inhaled fumes from a burning LiPo battery and since they felt no immediate ill effects everything is fine for everyone using the product.
www.nature.com
And what is HF you ask?
emergency.cdc.gov
HF is not something to be around ... it may not kill you immediately, but it can do serious damage in very short order.
Toxic fluoride gas emissions from lithium-ion battery fires - Scientific Reports
Lithium-ion battery fires generate intense heat and considerable amounts of gas and smoke. Although the emission of toxic gases can be a larger threat than the heat, the knowledge of such emissions is limited. This paper presents quantitative measurements of heat release and fluoride gas...
www.nature.com
And what is HF you ask?
CDC | Facts About Hydrogen Fluoride (Hydrofluoric Acid)
Information on terrorism and public health. Provided by the Centers for Disease Control and Prevention (CDC).
emergency.cdc.gov
HF is not something to be around ... it may not kill you immediately, but it can do serious damage in very short order.
@eEridani - Thanks for those articles, very helpful.
I agree that wasn't a very bright thing to post on a company website and any of those gases could be very dangerous, but in order to establish the level of risk, you'd need to know the exposure levels based on the quantities of those gases in the air you're exposed to. From the info you've posted that looks to be pretty high risk that I'm not sure is reflected in real life experience (unless my Maths are out - happy to be corrected!).
Firstly, the available information from a SDS (MSDS) is generally aimed at describing occupational exposures, so larger quantities of the chemical. For the HF alone (I haven't looked up the others yet) the Peak exposure limits (should not be exceeded during any part of the work time) that I've seen is around 3ppm (parts per million), equivalent to 2.6mg/m3. Bear in mind this is for pure HF, but the article you posted does provide details of how it has measured so let's take it that they are on a par.
From the article you posted, HF release was measured for battery chemistries that are not usually encountered in our hobby - the closes equivalent being the Laptop pack, or "G" in Table 1. That battery was listed as being 5600MaH, at a rating of 124Wh, so running at around 22.2 volts (6s)
For a rating of 124Wh, it reportedly yielded 15mg/Wh of HF. Thats' a total amount of HF for that battery of 1860mg.
The SDS Peak exposure value of 2.6mg/m3 means you would need at least 715 cubic metres of air to dilute the HF down to a tolerable exposure level. That's a very large room or a very good airflow through an average size room. Even if we go for a 50Wh battery, e.g. say a 6s 2200MaH, you're still looking at ~360 m3 of air needed. That isn't just about the room size but also depends on the amount of time taken to move the air, so how quickly air in the room can be changed. A smaller roomm would need faster air exchange to achieve the same level of dispersion.
That's worst case - in reality, a battery may not give off as much HF as that, hopefully it will be in a large room with good ventilation, so ventilation is very clearly the key here.
Respiratory protection needed - if you're looking for a mask that would protect you (either full face or wearing separate tight fitting goggles to protect your eyes) it would need to include an organic vapour cartridge.
Real life experience would tend to indicate that there may not be quite as much HF present as that study indicates or that air exchange is happening faster... that may be because of the way the amounts were measured, compared to the exposure points encountered by users - that will depend on factors such as whether the gas sinks or rises, how quickly it disperses, etc. In any case, it is a really good indicator that great care needs to be exercised when dealing with a burnt LiPo.
Key Indications of exposure are watering eyes and irritation of airways which are apparent prior to reaching peak exposure levels so anyone experiencing that needs to immediately get clear and work out a better approach.
The thing that surprises me is how willing people are to handle burned battery residue, with no gloves, getting it on their clothing, etc. If I was dealing with a burnt battery I would want to be wearing disposable gloves, not touch anything else and wash my hands thoroughly after glove removal prior to touching my face, or doing anything else really.
I agree that wasn't a very bright thing to post on a company website and any of those gases could be very dangerous, but in order to establish the level of risk, you'd need to know the exposure levels based on the quantities of those gases in the air you're exposed to. From the info you've posted that looks to be pretty high risk that I'm not sure is reflected in real life experience (unless my Maths are out - happy to be corrected!).
Firstly, the available information from a SDS (MSDS) is generally aimed at describing occupational exposures, so larger quantities of the chemical. For the HF alone (I haven't looked up the others yet) the Peak exposure limits (should not be exceeded during any part of the work time) that I've seen is around 3ppm (parts per million), equivalent to 2.6mg/m3. Bear in mind this is for pure HF, but the article you posted does provide details of how it has measured so let's take it that they are on a par.
From the article you posted, HF release was measured for battery chemistries that are not usually encountered in our hobby - the closes equivalent being the Laptop pack, or "G" in Table 1. That battery was listed as being 5600MaH, at a rating of 124Wh, so running at around 22.2 volts (6s)
For a rating of 124Wh, it reportedly yielded 15mg/Wh of HF. Thats' a total amount of HF for that battery of 1860mg.
The SDS Peak exposure value of 2.6mg/m3 means you would need at least 715 cubic metres of air to dilute the HF down to a tolerable exposure level. That's a very large room or a very good airflow through an average size room. Even if we go for a 50Wh battery, e.g. say a 6s 2200MaH, you're still looking at ~360 m3 of air needed. That isn't just about the room size but also depends on the amount of time taken to move the air, so how quickly air in the room can be changed. A smaller roomm would need faster air exchange to achieve the same level of dispersion.
That's worst case - in reality, a battery may not give off as much HF as that, hopefully it will be in a large room with good ventilation, so ventilation is very clearly the key here.
Respiratory protection needed - if you're looking for a mask that would protect you (either full face or wearing separate tight fitting goggles to protect your eyes) it would need to include an organic vapour cartridge.
Real life experience would tend to indicate that there may not be quite as much HF present as that study indicates or that air exchange is happening faster... that may be because of the way the amounts were measured, compared to the exposure points encountered by users - that will depend on factors such as whether the gas sinks or rises, how quickly it disperses, etc. In any case, it is a really good indicator that great care needs to be exercised when dealing with a burnt LiPo.
Key Indications of exposure are watering eyes and irritation of airways which are apparent prior to reaching peak exposure levels so anyone experiencing that needs to immediately get clear and work out a better approach.
The thing that surprises me is how willing people are to handle burned battery residue, with no gloves, getting it on their clothing, etc. If I was dealing with a burnt battery I would want to be wearing disposable gloves, not touch anything else and wash my hands thoroughly after glove removal prior to touching my face, or doing anything else really.
The photo from earlier showed three fairly large batteries - 22.2v 1.5Ahr - 100Whr total - and with Lithium being the main ingredient I'm still concerned the HF byproduct concentration is dangerous.
I'm not defending nor criticizing taking extra precautions against a battery failure. In fact, I feel a bit concerned that I take zero precautions myself. I do however take any sign a battery is failing and dispose of it as soon as possible, swelling being one of the signs of improper chemical breakdown.
Your analysis of the actual gas concentrations contrasted with what the articles have to say is interesting, thank you, especially since the article is concerned with a battery fire on airplanes or other enclosed spaces with fair air circulation.
But in homes, the gases released will likely form a cloud - and not be evenly dispersed. You said this, but the term cloud is more easily understood by the masses. There are physics behind the cloud formation - basically mass, temperature and density effects. Circulation will eventually break up the cloud, but room size isn't the only factor: a 20x20 garage is no safer than a 5x5 closet in the initial stages of gas release.
I would bet there are readily available compounds that will absorb and neutralize some of the HF and some of the other compounds released. Even a layer or two of common charcoal filter pad could help, followed by a lime or bicarbonate of soda based filter. Maybe a layer of carbon and a layer of the same media that was coated in baking soda (dipped in a saturated solution of soda water and then left to dry). These layers could be stacked outside the glass and steel vents in a less heated zone. Any reduction will be better than none.
Well - back to my Air 2 strobe clip design. I will NOT put tape on my drone.
My thoughts as well, wouldn't the heat build-up from enclosing the charging batteries be more likely to cause an issue, rather than the recognised, but extremely unlikely, chance of battery faults causing a fire?
While enclosing batteries in a container/box may also trap some heat, a healthy battery will stay well within a safe range. A box will allow a little more room for the heat to dissipate than a bag and the walls of commercial Bat Safe boxes are metal, which may help conduct some of that away.
If the battery is in a condition where the difference made by enclosing it would cause thermal runaway, then firstly, it should be showing some signs beforehand and you should be disposing of it (i.e. more than slight swelling, not holding as much charge, etc) and if you were to chance charging it, you definitely NEED a battery box of some kind......
I've been charging in a battery bag like this for years..... https://amzn.to/3zOzsGW
I also charge in my garage on a concrete floor with plenty of space around it. Four years ago one of my Phantom 4 batteries caught fire. Luckily I was only charging one, it was a mess. Huge amount of smoke from such a small battery.
I also charge in my garage on a concrete floor with plenty of space around it. Four years ago one of my Phantom 4 batteries caught fire. Luckily I was only charging one, it was a mess. Huge amount of smoke from such a small battery.
You can charge them outside in a large metal trunk that locks and is fixed to the slab so no one can steal them. Then they won’t burn down the house again.
I got this one from Home Depot for $150-$200.
Totally kills the problem and I can charge the whole fleet at once. No smoke in the house, garage or shop is possible.
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But, as someone pointed out earlier, they have an internal seal. Any gases venting from the battery during charging will pressurise the box. If it does catch fire, the overpressure could be lethal.
TnDronePilot
Well-Known Member
Well I just learned a whole bunch. I was researching those lipo bags on Amazon and just came here for the truth. I'm going to retrofit a 50 cal metal ammo box tonight. So are the holes on top in case the battery goes up in flames or for heat dissipation while charging? I've been charging my batteries all over the place including my SUV when on a long shoot. Holy crap! I've been playing Russian battery roulette.
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