Rechargeable Cordless Eco Hot Water Bottle The cordless "Nukunuku" eco hot water bottle can be carried anywhere and reused. It requires no troublesome water changes, and a 15-minute charge from a power outlet provides warmth for up to 8 hours. It can be used as a warmer on your lap, as a bed warmer in your futon, or to warm your feet like a kotatsu by placing them on top of it. The cover is washable. Hot Water Bottle Rechargeable Hot Water Bottle