Lithium battery packs for various guides, teaching and other purposes, can be customized to 7.4V14650-1050mAh for small loudspeakers, 7.4V18650-2200 mAh for large loudspeakers, 11.1V18650-2200 mAh for large loudspeakers, etc. Battery capacity, plug and protection board operating current can be customized according to customer's product requirements.