Best replacement battery for your smart car? Optima Red Top. The OEM Banner battery on the right is crap. Get an Optima 34/78R and a slightly longer negative cable and fit a Red Top. More cranking amps, longer life, resistant to cold and vibration, built to recover from deep discharge. Sealed AGM technology means no explosive gases to vent, which is important because the batter on these cars is right in the passenger compartment. Optima Red Top FTW!