Because this is an older "W" characteristic charger, the charging current will naturally drop as the battery voltage rises. You should monitor the battery temperature and charge status manually.
Using a manual charger like the KL 1206 requires more attention than modern "plug-and-forget" smart chargers, as it may not automatically stop when the battery is full. Bosch Kl 1206 Manual
The is a robust, legacy 12V car battery charger designed for standard lead-acid batteries . While newer "C-Line" smart chargers have since replaced it in the modern lineup, many KL 1206 units remain in service due to their durable transformer-based design. Core Specifications Voltage Support: 12V. Charging Current: Effective 6A; arithmetic 4A. Because this is an older "W" characteristic charger,