How can I contain a 26650 fire?

[TomBrown]

I regularly charge 18650 and 26650 batteries unattended. I'm charging several at my house right now but I'm at work.

The danger is a bit scary so I charge the cells in the middle of a concrete floor, a few feet away from anything combustible.

I'd like to move the chargers permanently to a shelf with some sort of fire containment barrier. I'm thinking of a partial enclosure of either concrete board or perhaps sheet metal. It would be open to the front for access.

Does anyone have an idea of how difficult a battery fire is to contain? Will it melt through 20ga steel?

The fires I've seen haven't been that bad.

 

[ven]

IIRC a bucket of sand is a good precaution. However, decent cells and charger, if untended have a timer on the plug set for X amount of time...........just a thought. This for example after 3hrs will shut off.

I charge..........well lots, maybe 4-10 cells a day, inc the odd 26650 cell at 2a rate. No buckets here though..........

 

[Str8stroke]

If charging at a low amperage, how about a Lipo fire bag? Only issue I see is heat build up.

I use a .50 cal ammo can with holes drilled for ventilation and wires. Concrete floor or sits on ceramic tiles. Then a 5 hour wall timer.

 

[HarryN]

There is fire containment, and then there is dealing with the smoke damage. I had 2 slices of bread char in a toaster that didn't pop (yes, I left the room to deal with the kids) and when I returned it was an amazing amount of smoke. It took 3 days of professional cleaning, and us moving to a hotel room to deal with it. The toast never flamed, just turned black.

I guess my point is that I never charge batteries inside the house unless I am nearby, and those are cell phone and laptops. I only charge free standing batteries in the garage and in a steel bucket - and when I am nearby.

 

[andrewnewman]

HarryN makes a good point about the potential for toxic smoke damage. There is no sure fire way to prevent all accidents but one reasonable approach might be to charge the batteries in a garage with a cement floor and no air-exchange with living quarters. I wouldn't put an entire lithium ion charging station inside a Lipo fire bag for heat dissipation reasons personally. If the charger melts down and is hot enough even protected cells will vent. Your original idea of a 5 sided box with open front made of cement board is a good one. I might put the whole charging station on a fire brick to manage heat and I would make sure the front was not too close to anything flammable or anything you cared about (like a car hood for instance). A timer is a good idea but be sure it isn't near enough to the charger to be effected by the heat of a potential fire. If you are home, a small bucket of sand is an excellent idea. Also if you are charging many cells at high current I'd try it first when you can monitor how hot the power supply for the charger gets. If in doubt get a larger power supply. Finally if you really want to take a final step, wire a safety box with a fusible link that will cut the power to the outlet downstream and place it at the top of your box. These safety boxes are typically used in oil boiler installations and placed above the boiler. (See: https://www.beckettcorp.com/wordpress/wp-content/uploads/2015/06/thermal-switches.jpg)