New York City wants lithium-ion e-bike batteries to be stopped at the border

I can't really fault them for that. Unfortunately, LiIon is everywhere.

> “As soon as the battery is charged, I disconnect it. You shouldn’t leave it charging for too long,” Lopez told The Associated Press in Spanish, “because if you leave it on there too long, that’s when you can cause a fire.”

That's a sign that they are using really bad charge controllers and chargers. There are supposed to be all kinds of safety measures in place that stops cells from overcharging. But: when they go there is no stopping it (effectively, there are ways but they won't be handy). I've built a (large) e-bike battery, 170 cells. At full charge that's 2.2 KWh worth of charge in a pack that is about as large as the hole in the frame of a bike. It's fantastic to use but I'm very much conscious about how dangerous such a pack is and how crappy the designs are of many commercial packs using exactly the same cells. LiIon is inherently unsafe and the older those packs get the more risk they embody.

There are safer chemistries, Lithium-Iron-Phosphate for instance (or LiFePO for short). Roughly similar from an application point of view, slightly more expensive. Unfortunately, most e-bikes (which are used and stored in proximity of unsuspecting consumers, charged in hallways of apartment buildings) use Lithium-Ion. I think that we'll see many more of these fires as packs get older and they have been exposed to more vibration and possible water ingestion. Even the big brands have problems.

If you have one of these and it's a cheap or older pack then make sure it is damage free, check it (even if that means opening the case) to make sure that there is no moisture in it that can cause the electronics to malfunction or the contacts to corrode and make sure the sense wires are all good. Broken or damaged sense wires are the number one thing I've come across in packs that failed, and in more than one case this was due to sense wires shorting out which is one very small step away from a runaway fire.

Laptop batteries are sensitive too, but given the nature of the laptops themselves people tend to treat them with more care. Impact is a big no-no and if you suspect a pack has been subjected to impact treat it with great respect and keep it out of any residence, usually your local disposal service will know how you can get rid of it in a responsible manner.

I've got a huge file on Lithium-Ion safety prepared, it's been in the works for a very long time because getting it right really matters, for now just take my word for it: don't take any chances with this stuff, play it as safe as possible and treat any battery that has been involved in an accident or a fall as you would a live explosive. If you think I'm exaggerating you can do some googling for examples of packs that go 'foof' without any warning at all. Sometimes in crowded elevators, sometimes in residences, garden sheds, bike stores (especially risky because that's where people will bring their bikes to be repaired after a fall or accident). And if either battery or charger gets suspiciously hot don't take any chances, disconnect and have it checked and keep it in a safe place until it has been checked.