Most consumer devices do not take 40 cells. Letting average joe play with 40+ amps of current at 48 volts is not a great idea.
Right means that the cells must be installed in the correct orientation, must all be the same make, model, and age, and must meet the continuous discharge rate requirement for the application.
I'm sure someone will find a way to get it wrong, but people also find ways to mishandle fuel for internal combustion vehicles with predictable consequences. The accident rate doesn't need to be zero for this to be a good idea.