If you mean battery polarity then the protection circuit in the battery should prevent problems but if you mean mains polarity then that won’t matter – can you identify exactly where the smoke came from?

GW, its not unheard of for the batteries to spontaneously to let go or "vent" as its known, in use!

Yes most of the venting incidents will be very minor & the battery will just fail to work, don’t be alarmed by the videos on youtube as people only want to video dramatic things.

It’s not unknown for this sort of stuff to be spec’d on the old european voltage stabdard (230 +/-6%) rather than either the old UK spec (240 +/-6%) or the new pan-european including the UK spec (230 +10%/-6%). When they changed the standard they changed it in such a way that we in the electricity companies didn’t need to do anything, old equipment would still work but equipment suppliers had to increase the tolerance that their kit would work over. If they didn’t then someties things fail.

That said I am assuming there is a decent regulated power supply in most chargers (they’re pretty cheap) and it would surprise me if one I bought failed.

So maybe it was just a duff one – contact the seller and see if they’ll honour whatever king of warranty a Hong Kong internet seller provides.

Iain