The KL 1208 makes a high-pitched whine. Solution: Normal. That is the switching transformer oscillating at 50-60kHz. If it screeches or clicks loudly, stop using it. The manual lists "audible coil noise" as acceptable only below 40 decibels.
12V Lead-Acid (Standard, Gel, and Maintenance-free). Minimum Capacity: 5 Ah. bosch kl 1208 battery charger manual exclusive
: Designed for all 12V batteries with a capacity of at least Charging Performance : It can charge a 50 Ah battery to 80% in approximately Global Use : Operates on AC input voltages between 90V and 260V The KL 1208 makes a high-pitched whine
I can then provide specific diagnostic steps for your situation. If it screeches or clicks loudly, stop using it
: Lights up approximately 30 seconds after charging starts. Flashing : Charging is still in progress.
: Batteries generate explosive gases during charging. Never smoke or allow open flames/sparks near the unit during operation.
For models with a "TEST" function, you can perform a simple health check without mains power: