A good rule of thumb is definitely the larger the speaker, the longer the battery life. But this isn’t always true, points like far more updated Bluetooth firmware versions can significantly influence power efficiency, in addition to a large Bluetooth four.0 speaker won't past as long while you’d hope https://www.bluetoothspeaker.top/popular-bluetooth-speaker-colorful-led-wireless-bluetooth-audio-high-power-subwoofer-speaker/