Not a bad idea. It must kill the batteries pretty quick though. A 118W, 127 couple cooler running at 9.6 volts draws around 7 amps. Even with the highest capacity NIMH batteries that's only about 12 minutes run time. Peltiers have a way to go before they're practical in battery powered applications. By my estimates keeping a beer at 0°C in an insulated container has a heat leak of <5 watts. If they could ever make a Peltier cooler that operates near the Carnot efficiency this would only require less than a watt of power even on a very warm day, making it practical for battery power. Current coolers require about 10 to 20 times that.