Yuasa yucel sla batteries yuasa y21 12 the yuasa y21 12is a 12v 21ah sealed lead acid battery designed for standby use this battery is waterproof the agm principle relies on the use of blotters between the lead plates in which the acid is soaked the agm technology enables you to have a more efficient battery for a wide range of applicationsapplications robotics engineering alarms backup systems medical devices telecommunications toys signalling it systems yuasa yucel y21 12 v