We just got a new battery on our Nissan Maxima, but yesterday while I was driving it everything electrical shut off. Lights wouldn't work, radio, dash board clock, speedometer, nothing would work. So I pulled over and shut off the car, I was able to restart the car just fine and drive it , but nothing electrical works, I don't know what it could be, please help! :confused:

Begin by testing all under-dash and under-hood fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-46563-3.html#post252145

For the past 5 years, the Maxima has had a good record for electrical components. This problem would appear to be related to installation of the new battery and since the car can be started the battery sounds OK.
This link lists a similar problem:
Nissan Repair: battery problem, nissan maxima, battery cables (http://en.allexperts.com/q/Nissan-Repair-825/battery-problem.htm)