It's most likley because it's trying to pull to many watts. These inverters will shut down automatically if whatever you plug in is something that's going to pull to much power. They are only good to 150 watts. They are actually pretty small and mount to the bottom of the passenger seat. The total wattage needed for the kettle to operate should be stamped somewhere on it. You might want to check and see what it is. They work nicely to run small things and laptops but aren't really desighned to run larger things. I keep an actual 600 watt portable inverter under my back seat that I can just connect to my battery if needed in case I need more power than my factory inverter can put out.
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