To prevent a fire in the home, would it be safer to charge my ebike battery dangling outside in a waterproof box on the end a rope out of a window?

[Nealh]

A different take on the Chinese fire balloons.

 

[guerney]

you have forgotten the water filled butt for it to fall into.

If you use a nylon rope of the right size, the fire will quickly cut the rope for you.


Better than Nylon would be Spectra/Dyneema (e.g. used for kite strings) it has a lower melting point, 147C versus 220C.

A different take on the Chinese fire balloons.

@Nealh - A different take on the water cooled battery, a burning one: Charge the battery indoors perhaps, on nylon netting stretched over a water butt made of suitable material? The nylon/Spectra/Dyneema netting would melt in the event of fire, allowing the flaming battery to fall into a large volume of water inside that water butt? Melting of cheap Linear Low Density Polyethylene barrels could be prevented by adding a concrete layer at the bottom? Or there could of course be reasonably priced barrels available, made using a more heat resistant material (steel barrels are a steal at less than £100, ebay linked below). As water evaporates, keep adding water until the fire is completely extinguished... also pump out water, to prevent water temperature becoming so high it softens/melts the plastic barrel? The eco-conscious could collect the toxic water outflow using barrels outside, those who don't care can simply drain water into the toilet, poisoning everyone and everything.

Tamco® Closed Head Poly Drums | U.S. Plastic Corp.

Specifically engineered for superior strength and durability, Tamco® Drums are an excellent choice for the storage, handling, and transpo...

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Oil Tank Barrel Open Top Steel Drum Diesel Water Container, Lacquered Interior | eBay

The Open Top 210 litre Steel Drum is UN approved. Supplied with lid and lever latch ring and internally lacquered. Although we refer to these drums as 210, they’re also referred to as 45 or 55 gallon, 200, 205, 216 litre etc.

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[guerney]

You are going the wrong way. Raise your battery above your house with an helium balloon. Using a thermally controlled switch to release the tether and charge cable, should your battery ignite. Thus it can float away to bother someone else. Also with enough altitude the battery will be kept much cooler, preventing the chances of ignition.

That's an excellent idea! Helium can be bought from Argos:

https://www.argos.co.uk/sd/helium-canister/