Car gets no electrical power at all...won't start or take a jump.

1996 Nissan Maxima Service Repair Workshop Manual DOWNLOAD

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you mentioned new alternator and battery, but it seem that the alternator is not charging, when you install the new battery the car started and run and after hours of running specially if head light is on the car shuts down. this is an indication that the alternator is not charging. (factory defect) have it checked or return part to auto supply.
if alternator is good and you have the car jumped and run it will not shut down even if your battery is dead because the charge of the alternator is enough to power the electrical system of the car until you turn it off. this applies to all cars

you cut cord have open circuit.your electrical cord has three wires neutral wire white wire black wires hot wire and bare wire for ground. if you cut either neutral wire or hot black wire in the electrical cord no power can flow to trimmer motor if you cut wire need to fix wire to get trimmer work again.

Check all fuses ,wiring anywhere short or check alternatour

Sounds like it needs a battery.

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Check battery ground wire or get a new battery.

Yes this may help try a new ignition switch .i had a 93 and it done the same thing to me .hope this help you ....

check battery out and battery connections real close

Check for power at starter solenoid on switch side (purple wire) should have 12-12.6 volts if you have power to the solenoid and it won't do anything then the starter is bad.

TEST YOUR ALTERNATOR AND HAVE THE BATTERY CHECKED IF THEY ARE OK
YOU MAY HAVE ELECTRICAL SHORT