These batteries are nickel-metal hydride (NiMH) type and can be recharged using a compatible NiMH battery charger designed for C-size rechargeable batteries. The charger must provide the correct voltage (1.2 V per cell) and be suitable for NiMH chemistry. Charging typically involves placing the batteries in the charger with correct polarity and connecting the charger to a power source until charging is complete.
Note that the Varta plug chargers mentioned in the sources are designed primarily for AA and AAA NiMH batteries, so you will need a charger that supports C-size NiMH batteries specifically. Always follow the charger manufacturer's instructions for safe and effective recharging. The charging time depends on the charger's specifications and the battery's degree of discharge but usually ranges from a few hours to overnight.
