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Comment by derbOac | Hacker News Reader

How safe would something like this be? It has a lot of appeal to me but I'm already getting nervous about battery fires as it is.

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As long as you have voltage and temperature monitoring with either a relay or preferably a power-fet for each and every cell it is safe and reliable

This approach is much easier for prismatic cells but I have seen it successfully done with cylindricals

I posted a link to the spec sheet in these comments and the certifications are shown. If your concern is the Li-Ion battery itself, that's a fair question.

I would definitely build a separate shed out of concrete blocks to keep it if allowed.

Concrete blocks are not tolerant of certain heat ranges (they can crumble) so maybe some extra hard portland cement would do the trick? A cistern filled by rainfall or garden hose could be built of the same material just above the battery compartment with a quick drain to totally douse the battery if needed.

Water can be problematic in lithium fires.

Maybe the upper chamber would need to be a hopper full of suitable material to try to contain a Li-Ion fire.

The concrete shed will be ok during normal operation. It would be there just to protect the battery from the elements and to make sure it wouldn't burn down my house should it enter thermal runaway.

It would be for the same reason I have my generator and its fuel in a dedicated shed today.

For the love of god insulate a shed if you must use one

The temperature swings won’t just hurt performance but risk thermal runaway if severe enough

Good point! But that shouldn't be too hard. Probably easier than soundproofing a generator shed.

Here are some facts about the BYD Seal EV:

- A Seal costs around $66k in Australia, before any subsidies.

- A Seal has a 80 kWh battery.

- BYD says the LFP batteries in the Seal should last around 25 years.

- BYD says they will ship a Vehicle to Grid kit (ie, when they do it can become a house battery). They already have a 3 kW "mains" power point in the car.

- I don't know how safe it would be, but in Australia people generally park their cars in a garage that is part of the house.

House consumption varies a lot, but if you remove aircon, pool filters and the like, 20 kWh / day will probably do you. So the Seal's battery should last 4 days.

In comparison, house batteries in Australia cost around $1000/kWh installed. If prices at the same rate a Seal should cost $80k for it's batteries, and you get a car thrown in for free.

If they're LFP batteries, then they should be pretty safe. That chemistry has a much higher bar for runaway fires.

LiFePO4 is extremely underrated in conversations about Li-ion. They are my go-to unless I need high power density high drain

Particularly larger LiFePo4 cylindricals and prismatics are fantastic. They have surprisingly good quality control despite almost entirely coming from largely untraceable Chinese manufacturers

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