It seems to be generally agreed that those aren't consumer-ready.

Protected cells are hard to find, there are multiple chemistries, it's easy to accidentally put a 14500 in an AA device and break it, etc.

16340 is probably the friendliest cylindrical lithium, but really I think what we need is a square GoPro style battery, with builtin protection, a data channel that can tell the host exactly how to charge it, and that can be safely paralleled or put in series up to a reasonable voltage.

If you used Dallas onewire for the data channels, all you'd need to do to make a pack is put them all in parallel and let the host chip figure it out.

Just like, solve the battery issue once and for all. You could even have coin cell sized versions.

> You can be pretty liberal about cells in parallel, it's series that bites you.

Yeah but at least the BMS he uses does balancing to (hopefully) keep the series packs from going into dangerous voltage territory.

A dodgy cell in a parallel pack however, there's no way a standard BMS can detect that, hence pre-install measuring and matching... of course you can go for individual cell protection as well or buy cells with built-in protection but the former is overcomplicated (and hard to get right) for a DIY project, and the latter not an option as the cells from vapes don't have a need for protection circuitry. Hence, matching is a must.

> He's using a 5s arrangement, it looks like - so his 100w fast charging will only be around 5-6A, not 30A, which those wires will probably be OK with (though i would have picked something thicker myself)

Fair point, but still, that's not looking remotely near the 0.5 mm² that one should use for 5-6 amps of current.

Well, at least once actual explosive goes kaboom, it's gone. A battery in runoff is a fire hazard for much longer time.

first off : terrible advertising.

second : how many times do mechanical-contact 18650s need to be attempted before it's settled universally that it's a bad idea for vehicles (like e-bikes that your advertisement mentions)?

I hated the VRUZEND design too and they at least had the insight to use 18650s with overlapped bus-bars for the sake of rigidity and continuity through deformation.

The design that you're using is, imo, most similar to the JAG35 pcb-over-terminal designs -- but as far as I know he doesn't bother trying to use PCBs over loose 18650s; only to interface with existing and pre-welded packs or packs with pre-welded stud interfaces, usually already fairly rigid prismatic packs [0]

PCBs aren't that rigid necessarily; it's easy to imagine conditions in which batteries might drop out of the network. Even with lots of bolts and thick PCBs -- uneven thermal expansion due to a poorly made cell, for example. The kind of conditions that would fry a lot of motor controllers under load should the voltage suddenly change somewhere.

No thanks. Let's stick with welding, it's now dirt-cheap to buy a battery welder and it's not nearly as irreversible as groups that sell things like this would make you believe.

[0]: https://jag35.com/products/fully-assembled-12v-4s2p-1200a-le...

Probably the best outcome. Nicotine is a pretty potent poison, not sure how much is in vape juice though.

> Your great-grandfather may have built his own house, your grandfather probably climbed the roof to replace some tiles which got blown off in a storm, your father may have stood on a ladder to paint the walls. They all seem to have survived long enough to reproduce so you are able to warn off people from trying to be self-reliant because it may hurt them.

Survivor bias. Look at average life expectancy up until the 1950s... it was shockingly low. Most people had many MANY many children just to see one or two live to adulthood - accidents and pandemics claimed their lives, workplace injuries and wars took them as adults. Your great-grandfather likely had four to five siblings [1], earlier generations were at around seven in the US [2].

It's only because of vaccines, OSHA, antibiotics and medicine that human life expectancy has exploded over the last decades. House fires are among the most stubborn killers that still remain, the numbers are going down extremely slowly [3].

[1] https://ourworldindata.org/global-fertility-has-halved

[2] https://populationeducation.org/wp-content/uploads/2020/04/a...

[3] https://www.usfa.fema.gov/statistics/residential-fires/