Induction warmers; plate warmers; induction cookers; controllers for induction warmers, controllers for induction cookers, controllers for plate warmers; batteries to power induction warmers; batteries to power plate warmers; batteries to power induction cookers; rechargeable batteries to power induction warmers; rechargeable batteries to power plate warmers; rechargeable batteries to power induction cookers; and battery charging systems for recharging rechargeable batteries configured to pow...