Power sucker

In my last several road trips, I used my iPad (first one, then two, and then the third generation) as GPS, and found that during the 4 to 5 hours of driving, battery life fell respectably 50%.  This afternoon, however, I tried another approach by tethering to my new Galaxy Nexus phone.  I found that that iPad battery dropped 60%+ even though my trip had shorten to 3 hours.  Of that top of that my Nexus phone was also sucking up batteries.  So at the end, I found it a very bad idea using tethering thing way.  Better directly leave the microSim in iPad instead.