They're not exploding that often. But you need to buy a decent one

If you get it from a reputable company it's no different to the phone battery. You can also get fire proof charging cases if you're really concerned about it.

As long as you avoid dropship crap, check for registered CSA certification in Canada.

E-bike makers are going through certifying bodies like the UL in the USA to have their batteries tested. It's not widespread but getting better, look for certified batteries.

It's not common but make sure both the bike and battery are certified - UL here in the US. My rule of thumb is to buy a brand that's sold in bike stores, even if you buy it DTC. Odds are better you'll get something where you can get parts that way, or store support if you don't do your own work.

I have a watt meter that's programmed to shut off the output when the power draw drops below a set threshold for 60 seconds. It also powers a couple computer fans that cool the charger, so it's set at 10W cutoff. Works great, and because it's WiFi, I can plug in the battery when I get home, set a timer on my phone since I always let the battery sit for an hour to cool down or warm up to room temp before charging, then trigger it remotely to start. https://a.co/d/akYxqL9

Just make sure you buy a timer based plug you can use so that the charger only gets power for a set time. I have one and it shuts off after 6 hours (though it can be set for shorter durations too). Just helps mitigate the amount of time a battery is plugged in.