What do you think of this situation and how can I be safer?

Hello,

I run an ebike tour company and have about 40 bikes. I started small and didn't give much thought to safety with regard to batteries but now when I look at 40 batteries left to charge overnight I wonder if I might be missing something with regard to safety.



I am using panasonic 18650 cells. Charging with unbranded chargers. Each battery has it's own charger.

Thoughts?

The harmonics on your local power grid must be a bit noisy!

As long as it's ventilated and there's nothing else to catch fire, it's probably OK. Just make sure nobody can be trapped in there should one catch fire.

A battery fire is extremely rare, but it just takes one cell to start one, and i think you've got at least 30,000 cells in that picture, and all those batteries are next door to each other. So you're playing the battery lotto with the odds biased against your favor.

If i ran your shop..
I would certainly have some fire protection, and sprinklers are not going to do it. I mean a metal enclosure like a heavy duty gun safe, at the very least. And a port to ventilate the metal case to the atmosphere in the case of a fire or offgassing event.

Hell, even charging them in a concrete/brick/metal room would be better. Because if a lot of those chinese firecrackers go off, there'd better not be carpet or wood or anything else flammable around.

We've seen a lot of homes and businesses burn down from these things. It's super unlikely that your average ebike rider will have a fire event, but being an ebike shop, you have a risk factor of 40x; it's something to think about..

Thank you for the input.

I am building a new office now and the battery charging area will be 100% non-flammable. At that point my concern would be that one battery catches fire and there is a domino effect. I have $20k invested in those batteries. I am considering building individual charging enclosures out of old army ammunition boxes but wonder if that might be overkill.

The harmonics on your local power grid must be a bit noisy!

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Could you explain what you mean by this? Much appreciated.

Individual enclosures would probably be the easiest in total, containing each 10Ah fire and gas is not so hard but at 100Ah scale it would be.

Marlz said:

The harmonics on your local power grid must be a bit noisy!

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Could you explain what you mean by this? Much appreciated.

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If you turn a radio on in the same room, plugged into the same socket, it might have a noisy hum - this is an example of harmonics impacting the local electricity grid.
https://www.youtube.com/watch?v=vkh8Jfmm3hk

Interesting. Looks like the business is going well. I have 8 batteries, have each one inside a cheap metal toolbox. rather than store and charge in the building (where we hire hiking gear) they are stored in a locked metal enclosed trailer. I picture them belching smoke and probably flame but expect they wont set off the ones nearby.

Look at some youtube vids of battery fires, then ask yourself if those metal boxes will contain the effect ?
Gas and smoke will certainly escape such that you wont be able to get near...and likely not in the room even.!
Smoke gets everywhere and will (obviously) trigger fire alarms so make sure your “fire proof room”. Is on a separate system to any other part of the building......preferably the “charging room” should be a completely separate building . ( metal shipping container? )
http://jimmymacontwowheels.com/battery-fires-create-concerns-for-every-electric-bike-owner/

have each one inside a cheap metal toolbox.

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any problem with heat?

Ambient heat isn't a problem in my situation and the boxes are gappy enough for my slow charge (but it is something I would test/ consider/modify for).

In my case i'm not really concerned with smoke, hopefully they are gappy enough to release it. I guess the ammo box mentioned is a similar concept & would be more secure, if that is necessary. I expect a cell would have to exit the box and enter another. I keep them more spaced than on your rack with radiant heat in mind (in a fire).

I'm relying on life experience and guestimates more than tech knowledge.

I'm not suggesting that you take out a huge loan and build a state of the art battery facility immediately, but...perhaps each week you should take a few steps in the right direction. First, get a cheap $20 IR "no contact" pistol thermometer, Heres a random link https://www.ebay.com/p/Etekcity-Las...meter-Temperature/2254419320?iid=202203917271

and also a cheap FLIR, which uses your phone as the screen. Not necessarily this one, but here is quick $300 google result...

https://www.ebay.com/p/Flir-One-Pro-LT-Pro-Grade-Thermal-Camera/22030648463?iid=362540982275

When a new pack has been working fine for a few weeks, we can assume that it doesn't have any glaring manufacturing defects. So if one of them catches on fire, what is happening inside? Heat expansion and cooling contraction can eventually cause one of the bus spot-welds to crack off, causing the remaining spot-welds to carry more current than before, leading to hot spots (each end of an 18650 typically has four spot-welds).

Vibration over time can cause a break-through on the internal insulation layers, allowing some part to short. The more vulnerable part is the shoulder of the positive end. The entire bottom and sides are charged with the negative electrode, and there is only a small gap at the positive end between the two electrodes. If there is insufficient protection in that particular spot on every cell, one of them could suffer a catastrophic short, which would cause every cell in that P-string to short and go off (these packs are likely 4P).

When the internal separator between the rolled-up anode and cathode sheets has shrivelled up, it's as if that cell has been suddenly replaced by a fat copper wire. That's why the entire P-group begins feeding the fire. If the rest of the pack goes up, it will simply be from heat because that 4P string is so close to the rest while it is burning. Too much heat causes the electrolyte to boil off into a gas.

https://www.electricbike.com/inside-18650-cell/

There are several failure modes where the one bad pack will be running hot and charging hot, long before it dies. Its trying to warn you in the only way that it can. They will all get warm, but if three out of 20 are noticeably warmer than the rest, you know what to do. If you really need to keep them for a while, run an extension cord outside to charge the hot three packs out there, and unplug them when you leave for the day.

The first time you decide to retire a pack, dissect it, since I suspect you made a bulk purchase from the same supplier, and the rest are likely identical.

As a mental experiment, imagine that you will be burning a pack on purpose. Try to find a metal cabinet that is tall and thin, like gym lockers. Put in metal mesh shelves so air can flow upwards from the bottom (heat rises). Put in maybe five packs on five shelves. Leave a couple inches of airspace between side-by-side cabinets. Sometimes you can find used metal lockers like this, very cheap, at a salvage place.

On the tops of the cabinets, add cylindrical vent-tubes, possibly similar to the exhaust on a typical homes water heater, and route the vents to the outside. Maybe add a small fan on the bottoms of the cabinets, blowing upwards.

If you want to do something immediately, I'd replace the shelves with metal instead of wood. The battery packs on the top row are unlikely to set their shelf on fire, but the lower packs could set the wood above it on fire. Scoot the shelves away from the wall a foot or two. Maybe add some fire-resistant paneling to the back wall and the floor underneath. It wouldn't take much to dramatically reduce the chances of a fire spreading.

Here's a tip, if you only charge the packs to 4.1V per cell, they will last longer, possibly even twice as long, compared to the typical 4.2V per cell that is the norm.

On the chargers, once they are running for a half hour, they will be as warm as they will get. Feel them to see which side is hottest, it will be easy to tell. They look to be the same, so their internals will be identical. Epoxy a large aluminum finned heat sink to the hot side. This should help the chargers last longer. If a charger ever does go bad, cut off the heat sink and re-use...https://www.accelthermal.com/assets/images/116-500.jpg

Try this on five chargers, and check the temperature differential between the finned and un-finned chargers by using the pistol thermometer you just bought...

Wow, thank you so much to everyone! You have given me some really good ideas and advice that I will certainly implement in the weeks to come. :thumb:

I suggest you start research on safe, tested and approved battery charging by appealing to your local fire department, which can guide you to the information. Advice to "just stick it in a metal box" may be sufficient, or not. I think you will find it worth the effort to insure your security by tuning into existing guidelines. Your Fire Department is there to help.

I am not sure if ammo cans are airtight, but probably moreso than you would want. You need to vent any rapidly expanding gasses. Keeping them in an airtight can is called a bomb.

Before calling the fire department, you may want to VERY carefully examine local building codes, and your insurance regulations. If a violation is found, they can shut you down and it may not be quick or easy to open up again. Could also be VERY expensive. Also, any records they make are public, and available to your insurance provider.

Partly for the above reasons, a separate, metal building or container NOT ACCESSIBLE BY THE PUBLIC in any part or section might be a good idea. I'm seeing way too much wood and flammable materials there, likely in the same building where employees work and customers can be. Not ALLOWED there and NOT ABLE to get there are two very different things, you want the second one.
At minimum, you need a securely locked door, and that may not be good enough.

The odds are fairly low, but forty times fairly low, plus forty times the several hundred bucks each battery costs, are getting into significant risk territory.

Simply put: your charging place needs to be somewhere you can have a roaring fire and not get anything else messed up. In your case it will be a big fire!

They do sell fireproof cabinets with external venting just for businesses like yours. It wouldn't make financial sense for the individual bike owner, but it might for you.

https://www.store-batteries.com/

Battery safety should start with the manufacturer of the batteries / bicycles. I see no reason that electric bicycles should be any more dangerous then cordless power tools, laptops, etc. No I am not typing on a laptop while sitting in a fire proof box.

My suggestion is to only buy batteries, bicycles, and equipment from reputable manufactures. Reputable means not Alibaba.com

Also do inspect electrical stuff for damage and replace, repair as needed. When stuff gets old. Replace.

You might try watching some Youtube videos of lithium pack fires to get an idea of what happens.
https://www.youtube.com/results?search_query=lithium+battery+fire

One pack is bad enough, but you don't want one to spread to another one and create a domino effect. Some kind of non-combustible separators (sheetrock, tile backer board, bricks, metal) between packs would stop propagation. Anything directly above a burning pack will be exposed to flames.

Individual metal boxes with vents would be the best. The vent keeps the box from exploding but should be designed to prevent oxygen from the room from getting into the box during a fire. This way the pack just smokes a lot but no flames. Enclosures made from stuff like sheetrock or tile backer board might work just as well an something you can DIY for relatively low cost. If the packs are small enough, you might be able to use cement cinder blocks laid sideways and stacked.



I have also seen some decent looking Nomex bags that can contain a pack fire. These would be easy to set up but no idea about the cost.

Marlz said:

I am building a new office now and the battery charging area will be 100% non-flammable.

Click to expand...

Might want to follow all the fire codes for new construction. Local building inspector is a good source for information. Garages are usually built so a auto / gasoline fire don't spread to the building. 5/8 inch drywall on walls and ceiling. Steel door with springs on the hinges so it is always closed. Concrete floor. No heating / cooling vents between garage and building. Lots more codes that I don't know about. Ever notice the step up between a attached garage and a house? That's in case gas spills on the floor. Don't want it running into the building.

Thanks for all the continued info coming in.

To add a bit to this, I am in a developing country. Therefore, almost no building code, fire department, etc.

The charging area I am building is entirely cinder block walls with a metal roof and metal shelves. As mentioned before, I am now looking into putting the batteries into individual metal ammunition boxes.

Thanks again!

Well, you can look up the fire codes for places that are more preventive about it than others, and follow those, as a guide.


Regarding the results if a fire does happen, IIRC, SF Bikes in California was destroyed in such a fire.
https://endless-sphere.com/forums/viewtopic.php?f=1&t=66285
I don't know if they ever rebuilt.

Well, my bike battery burned my house, destroying the garage and smoking the crap out of the living area.

But really, fires are incredibly rare, when you consider the number of these batteries out there. Even the notorious hoverboard fires were rare, compared to the numbers sold that Christmas.

Two main things to worry about. Human life is the big one. I hope nobody lives in the building, and similarly, I hope nobody is sleeping next door in an adjoining business. Like you live above the shop, or maybe there is a very close distance to the wall of a motel, apt, or something like that. Cinder block building helps with that, but not if it shares a roof with anything else.

The second one, is also really big.. Whatever you have for insurance, improve it. ( if possible where you are that is) Have your agent actually inspect your place, and follow what he may recommend. If it does happen, you simply gotta have good insurance. I did, and boy was I glad I had just recently upped the pay out on mine. It sucked to go through the rebuild, but we actually came out of it with extra cash, because we did not fully replace everything that burned.


As for your setup, again, make sure your insurance approves. The one thing I see is packs very close to each other, and wooden shelves. That could be improved relatively cheaply. You might look into some kind of building salvage lockers. Lots of little cubicles, but no real need to have doors. Just a simple piece of metal between each pack, and a bit more space. Or perhaps just metal dividers on standard metal shelving.


And of course, fire alarms, preferably the kind that calls the fire dept for you.


All this stuff is costly, and may take time to implement. But I'd be talking to your insurance agent TODAY.