BikeMaster High Performance Maintenance Free Battery BTZ7S High Performance Maintenance Free - Additional plates inside battery provide up to 30% more power (cranking amps) than the Yumicron battery. Dealer fills battery from included acid tubes to create a sealed, spill-proof battery.Never needs refilling. High level of power (cranking amps) possible for todays big bikes. Yuasa and BikeMaster batteries are all made using the same construction techniques. The advantages to Bikemaster are the greatly reduced prices.