I know that @Syonyk has direct experience in rebuilding e-bike battery packs. I wonder what he thinks of this source.
Splitting new old stock stuff and salvage cells? Store it outside... not against a building?
I'm not a big fan of abusing lithium, and I really don't run in the "FREE POWER BATTERY!" circles or anywhere close to them out of respect for my blood pressure. Those groups habitually and casually abuse lithium, put it in sketchy cases that are easy to short, and talk about how AMAZING each others builds are. I don't even try to correct them anymore, because they've built a shell against anyone telling them they're wrong. Even if you quote manufacturer datasheets at them.
IF the new old stock packs have never been fully discharged (I consider about 2.0V/cell a hard limit for "I'll attempt to charge it again," if I know how it got there, otherwise I won't put power to anything below 2.5V/cell), and are generally matched in terms of age and storage condition (temperature matters a lot for lithium wear), then it's probably safe enough to split them, reassemble them, etc. At this point, some of my cells are pretty much new old stock (a few years old), but I also know that they've been stored, unused and not attached to anything, in identical conditions, so I've no worries about using them in projects. And I check voltages before using them. But if you don't know the history of the packs, you shouldn't be mixing and matching, even if you've done a snapshot of their current state. It doesn't tell you how they're degrading, just where they are currently. With a competent BMS on the pack, it's probably safe, but... eh.
I treat lithium with an awful lot more respect than most of the people doing videos, spot weld only, etc. But, against my predictions from 5 years back, I'm not aware of a huge number of DIY Powerwall house fires. And most of those people abuse the hell out of the batteries.
*shrug* You get what you pay for. I wouldn't put a cheap salvage pack near anyone or anything I cared about, but presumably the don't fail that often.
As for front wheel hub motors, they're fine on the flat, and they absolutely suck climbing any sort of hill. Steering gets all sorts of weird and if it's slick and the front spins up (climbing a hill, more weight is on the rear wheel), you probably go down in a hurry.
I've not been doing much with ebikes lately, though. Working from the property and living on a 55mph road with increasing traffic means on my increasingly rare trips into town, I'm more likely to take something that can do highway speed. I'm just not comfortable doing 20mph on a rural two lane 55mph road.
