No dashboard size solar panel puts out 4 or 5 amps, this is what is required to run one of these coolers. No car battery is going to run it long before it goes dead. A constant 4 or 5 amp draw is going to kill it.

These coolers are only practical if you have a running car or a 110 volt plug for the cooler.

They would work with a solar panel and a battery if you had a 60 or 75-watt panel.

Or a generator.