here is the install from the manual. If you read carefully it does not say you "must" use a relay. Says if in doubt. And draws 3 amp, your cigarette lighter draws more lol
Connect the RED wire to an isolated switched 12V source in your vehicle. A switched 12V source goes ON as soon as “key on” power is active. The circuit to which you will pull power from should be able to support a 3 amp draw. Make sure this connection is protected with a 5A fuse.
Circuits that share power with the vehicle’s stereo, ignition system, ECU, lighting, or fuel pump should not be used. When in doubt, create an additional circuit using an automotive relay available at any automotive parts supplier. See the next section for a relay installation diagram.
The BLACK wire should be grounded to a solid ground source. The best possible ground source would be the battery ground (-) post.