When changing from a 20 amp to 30 or 40 amp charger you must also change the inline slow burn fuse to 30- 40 amp to match the charger output.I did not do this at first till I lost my shore power for awhile the battery went dead. When the power kicked back on, the 20 amp fuse blew because the charger was putting out 30 amps. Ken Bousum #711