Ensure the charger is unplugged from the mains before connecting to the battery.
For further details, you can view the Kleinlader ML 1208E Manual via the archive. BOSCH 7 780 301 144 Battery Charger - Onlinecarparts.co.uk
The Bosch KL 1208 can test a battery's state without being connected to mains power: Connect the cables to the battery. Set the switch to .
For further assistance, you can search for official manuals using the Bosch Service Manual Search by entering your device's E-NR number. Bosch Home Appliances step-by-step checklist for winter battery storage or more details on deep-cycle battery Instruction manuals - Bosch Home Appliances