Leaving the charger on will generally not effect the battery. This notion that overcharging the battery is harmful came from the days of Nickel Cadmium batteries. These days most batteries are Lithium ion. Regardless, as my video says, these speakers loose their battery, its a known fault.
I do not think that the front cover can be taken off in Onyx 3 and above. It was possible up to Onyx 2. Though I may be wrong about this as I personally did not try to open it.
True, speakers will power up from the charger instead. Don't know if the battery will or will not survive. Its a known problem with these speakers that battery dies, expect it.
But it's not wireless....... majority of consumers bought it hoping it was wireless.... I have speakers that are wired louder than the harman... I bought cause its loud for a "portable speaker" To me anything that still needs a wire isn't portable
