Can I leave the battery to charge overnight?

Yes, although you can fully charge the headset’s battery within 2-3 hours, it is not damaging to the battery to keep it in the charger overnight.

Is the headset battery replaceable?

The battery in the BeHear headset is rechargeable (tested up to 600 cycles) but not replaceable. We designed it this way to provide protection against water and dust damage for the life of the product, as well as to keep the cost to the consumer low.