... sorry to know about your dead battery, if this is happened on 2 devices maybe it's due to your battery management with all my respect.No just black, new one gunmetal, 2nd battery dying, will be down to 2 working. The crystal coils are the only way to use it.
Prefer to put your device under recharge as soon as the battery jauge reaches the red colour which means low battery, you may be able to get 1 or 2 more dabs but this is not good for the battery. I have myself 4 working Qomos, my first is a beta black Qomo, it's still working well despite it's one I don't use a lot cause the T° settings was set too high but battery starts to drain by itself which is a sign the battery is dying, although with some proper care I can expect to get it still in job for another year I believe (device is just less than 3 years old if I remenber well).
Have fun!