acoustic level 45 dBA battery curve Z battery type Lead-acid battery product certifications BIS curve equation Efficiency curve load maximum 100 % curve X-axis maximum 100 % curve X-axis minimum 0 % curve X-axis title Load curve X-axis units Percentage curve Y-axis maximum 100 % curve Y-axis minimum 50 % curve Y-axis title Efficiency curve Y-axis units Percentage extended runtime […]