Unplug your Duracell PowerSource 1800 from any electrical devices it is powering.
Turn off your Duracell PowerSource 1800 and set on a table top or other level surface.
Open the Duracell PowerSource's battery compartment and pull out all three 20-hour amp batteries. Set aside for appropriate disposal or recycling.
Take one of the three batteries to a battery retailer near you and purchase three appropriate 20-hour amp batteries.
Unpackage and insert each of the three replacement batteries into the Duracell PowerSource's battery compartment. Close the compartment.
Plug in the electrical devices the Duracell PowerSource was powering and then turn the device back on.