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Comment by dheera | Hacker News Reader

I feel like for home battery backup there needs to be some kind of lower energy density solution that has zero fire risk.

Weight is not a factor for home energy storage, there is no need for lithium cells.

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Currently, that is LiFePO4. It is cheaper than LiPo packs used in electronics, half the energy density, twice as many charge cycles, and doesn't burst into flame. The lithium is flammable but requires external ignition.

Larger batteries, including some electric cars, have switched.

LiFePO₄ (LFP) is overwhelmingly safe and cheap. Lithium isn't the problem here exactly.

It seems unlikely that there's any practical chemical batteries with 0 fire risk.

But I do think there should be home energy storage that doesn't involve chemical batteries. Where are all the pumped hydro, flywheels, and compressed air storage for consumer use?

There’s no perfectly safe energy storage. The danger comes from the concentration of energy. Water can cause flooding or you can drown in it. Flywheels can disintegrate into shrapnel. It’s always risk management.

LFP is the present solution, but sodium ion is the next step. Given the abundance of sodium in the sea there should never be any problem sourcing it.

https://cambridgerenewables.co.uk/product/eleven-energy-4-5-...

Weight is not a factor for home energy storage, there is no need for lithium cells.

That depends on your living situation. I live in a third-floor apartment, so weight is very definitely a factor.

Weight always is a factor since heavy batteries cost more to transport, period. It's always relevant, not least for the installation too.

We're talking on the order of millions of kilograms for the building materials that needed to be transported to build it. The batteries needed for backup power for its occupants won't come anywhere close to that, even at far lower energy density than lithium.

The apartment building can have unified power backup in its foundation/basement.

If you reduce the energy density by a factor of 10, the weight for power backup needs will still be far lighter than the concrete.

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