When the internal non replaceable battery dies the product dies; that's also one reason to prefer wired over wireless. I wrote product instead of headphones because the principle is applicable to every product whose battery can't be replaced by design. All those discarded single use vapes are a good example of that, and... surprise! All of them actually contain rechargeable cells but no recharging circuitry and port, the reason being that rechargeable Lithium cells are much cheaper than primary non rechargeable ones because of economies of scale. Just another example of greed being so damn efficient at producing e-waste.