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Comment by jstanley | Hacker News Reader

> they must be calibrated to account for the higher internal resistance of reused cells

How can the cell tell whether it is "reused" or not?

If it is true that the cell-level fuses must be calibrated to account for the fact that the cells are reused, would it not also be true that fuses must be recalibrated after some time even if the cells remain in their original application?

> Please don't fuck around with batteries unless you know what you are doing (you don't)

The "you don't" part isn't helpful, because it encourages a worldview in which technology is magic that can not be understood or harnessed.

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> The "you don't" part isn't helpful, because it encourages a worldview in which technology is magic that can not be understood or harnessed.

An essential part of that is actually understanding it and knowing what your limits are.

When you do extensive research, understand all the risks involved, and seek help to review your work, it is definitely possible to do projects like these - even as a hobbyist. The problem is that this looks to be closer to "hold my beer while I grab whatever cheap module I come across on AliExpress".

I design electronics for a living, and I personally wouldn't want to touch a project like this with a ten-foot pole. The risks are just not worth it. There are plenty of other fun things to do which aren't going to burn down my house.

> If it is true that the cell-level fuses must be calibrated to account for the fact that the cells are reused, would it not also be true that fuses must be recalibrated after some time even if the cells remain in their original application?

If you are being conservative, the fuse is already well below any peak ouput a cell might give you so aging cells are considered. Also in large packs, cells should (in theory) age roughly equally. But If you match a LG HG2 and a Sony Conyon and both fuse them for 50A and then wait a few years of usage your gonna have a bad day

They didn't say you couldn't learn, they said don't fuck around. That seems like pretty reasonable advice to me.

I wasn't objecting to "don't fuck around with batteries", I was objecting to the unequivocal "you don't [know what you're doing]".

I totally second that wording and I do know what I'm doing.

This setup is only safe in a structure that doesn't have people or other stuff in it and that you are not going to be upset about if it burns down.

I wrote it that way because the hacker ethos here makes a lot of people assume they know more than they actually do about all things tech. It's easy to learn how batteries work and how to make big packs of cells but the practical and institutional knowledge required to do it safely is not something one should just "hack" into. That's why.

It's extremely helpful! It helps keep the author of TFA safe.

The "you don't" is leaning on the idea that if you actually know what you're doing, an internet comment saying you don't isn't going to dissuade you. If you aren't confident enough to ignore an unequivicol "you don't understand this", then you definitely don't know enough to mess around with this. (The converse, of course, isn't true. There's always going to be someone who is still overconfident enough to ignore it even without having enough knowledge).

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