Hello there sorry for only now replying. So like most bluetooth speakers the louder the speaker is playing the more battery it needs to use to power the speakers. Also when using bluetooth normally your smartphone, tab will drain some of the battery also cause it is using the bluetooth. Most case if your smart device can plug in to the speaker then it will sound similar cause it depends on the 3.5 cable you using if its a good quality cable and if your device have a good sound card also the port but I am sure you will get a little extra battery life with the bluetooth speaker being plugged in to your device / 3.5 input. When using this bluetooth speaker it have to be on even if you want to use it with out it being on cause it need power to drive the JBL speakers so you can get that loud sound and bass from it. Thanks for the comment, hope this answered your questions an thanks for the view appreciate it alot. Stay safe out there.
