Honda EU10i Owner's Manual page 32

Never connect the different generator models and types.
Never connect a cable other than the special cable for parallel
operation.
Connect and remove the special cable for parallel operation with
the engine stopped.
For single operation, the special cable for parallel operation must be
removed.
Depending on the equipment to be used, an overload may be
caused, the overload indicator light (red) may light, and it may
become impossible to take out any more electric power.
Motors generally require two to three times of their power
consumption for starting.
1. Connect the special cable for parallel operation to the two
generators.
30
UNIT
UNIT
SPECIAL CABLE FOR
PARALLEL OPERATION
(SOLD SEPARATELY)