You can use M1+ for up to 9 hours on one charge with a further 36 hours within the charging case.
Please note, however, this time may be reduced by several factors including:
High volume levels
Higher volumes require more power to drive the speaker inside. Reducing to a lower level can prove beneficial for your hearing and extend the use of the earbud.
Always using one earbud as the master version
Swapping the master between left and right occasionally will ensure that one earbud does not deplete at a faster rate than the other.
Using the highest possible codec
Using AptX or AAC may deplete the battery quicker as more data is being transferred between your device and Melomania 1+. If you can restrict your device to SBC only, you may experience longer listening time.
'High Performance' mode gives you the best quality earphones sound experience, with a listening time of up to 7hrs (earphones) and 35hrs (total case + earphones).
'Low Power' mode extends listening time to up to 9hrs and 45hrs in total.
The option to switch between these modes can be found within the Melomania app under Settings.