> I think good advice is to keep your devices as cool as you can (ie don't leave your cars in sunlight when there's shade),

In some climates, such as where I live, the larger issue is the cold in the winter. From what I understand, Li-ion batteries don't like being charged below 0 C. And it is not uncommon for it to dip to -15 C or even -20 C here.

Really, from what I understand, batteries want to be kept above freezing but cool. So yeah, don't leave it in direct sunlight in the middle of summer. The more difficult problem is the winter (unless you happen to have a heated garage).

> You're going to use your devices, so you won't control the temperature or, largely, the charge percentage.

> I think good advice is to keep your devices as cool as you can (...), and keep the battery between 20% and 80% as much as possible.

Yeah that's kinda what I meant. Where it's easy or possible to do so (for eg lots of modern laptops & phones allow charge limits), it's better to follow these guidelines.

> Batteries are ultimately consumables, so don't stress too much. Just care for them as much as convenient, and that's it.

Yeah I agree (and that's what I meant by my last sentence), however, a lot of people (including eg my dad!) end up having battery issues while being unaware that they can do things to protect their hardware.

For example, my phone has enough capacity to last the whole day even at 60% of it's capacity. I've set it to stop charging at 80% (the lowest possible SOC) for this reason. On my laptop, I frequently reduce it to 60% as I use it plugged in.

> I don't think this advice is useful.

I'm afraid I don't get what's not helpful? We're probably talking across each other.