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Comment by digi_owl | Hacker News Reader

Yeah i have read enough scary stories about people dealing with 18650 cells (effectively AA sized lithium batteries used in high powered flashlights etc), that trying to build a powerbank from used laptop batteries with enough capacity to handle domestic appliances is not something i would undertake.

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I have a sneaky suspicion that their insurance isn't going to cover the fire this may cause. These are lithium batteries, with who knows what for quality control, being used by people with who knows what for education. This could be a tragedy in the making.

They're lithium-ion batteries, which contain very little elemental lithium and do not result in lithium fires (which are very difficult to put out). True lithium batteries (the kind that can cause lithium fires) are not rechargeable.

http://batteryuniversity.com/learn/article/safety_concerns_w...

[edited to add link]

The idea that insurance won't cover fires from unpermitted, DIY stuff is mostly urban legend. Most homeowners' policies are what are called "all hazards" policies. They cover any kind of damage for any reason, with explicit exclusions like war, earthquake, flood. Outright arson / fraud by the policyholder would also obviously be excluded.

Banks would object to policies that excluded unpermitted work, since it's relatively common and this type of exclusion would leave them with lots of exposure.

So, they may decide to drop you like a hot potato afterward, but a fire from your homebrew powerwall would likely be covered. Read your policy fine print to be sure.

The batteries being talked about are 18650s, which is mentioned pretty clearly in the article and apparent from every single picture of batteries in it. This makes sense, because the vast majority of laptops sold across the world use a set of 18650s as their batteries. These are also the form factor of batteries being used in current Tesla powerwalls (though I believe they will also switch to the 21700 form factor as production of that ramps up).

18650s are just as safe as any other battery chemistry in everyday use, but they're a high energy lithium cell. In particular, if you do bad things to them, they may light on fire. It's not that hard to take appropriate precautions to avoid that, and reasonably sized lithium-ion battery fires can generally be put out with a standard househould fire extinguisher.

It also appears the community is collaborating to spread good information about powercell design to avoid/manage fires inside the units, in the unlikely event a cell starts a fire. If the container for the powercell is designed correctly, it can contain a complete unit burndown: https://electrek.co/2016/12/19/tesla-fire-powerpack-test-saf...

In short, you're overestimating the risks and underestimating the level of safety attainable with these products.

> In short, you're overestimating the risks and underestimating the level of safety attainable with these products.

No. When it comes to things that might produce fire inside your house, there is no such thing as overestimation. You cannot be over protective when it comes to fire safety.

Source: I was a firefighter for +7 years.

"You cannot be over protective when it comes to fire safety."

Ridiculous. There are obvious examples of overestimation of risk, why not prohibit electricity in homes entirely for example? Should I get rid of my kitchen stove?

This kind of absolute rhetoric is banal, obviously absurd, and is not helping anyone.

Effective safety measures involve accurately quantifying and balancing risk.

In the article it says they don't put them in their house. They put them in a shed or other detached building.

> there is no such thing as overestimation. You cannot be over protective when it comes to fire safety.

Have you ensured your house is built exclusively of fire resistant materials, and avoided buying modern furniture with inflammable fabric covering and interior padding? Have you installed a Halon system in your home and all physically adjoining structures?

What an absurd statement.

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