It could take longer than you would like, possibly a tank of gas from the other vehicle depending of course on how large the other car's alternator is.

The best way to do it would be to take out the battery and bring it to an Autozone or some place similar. Ask them to test it which they will do for free but cannot do it unless it is charged. At that point they will charge your battery for free (it might take an hour or so . . . so plan to run some arrons in the area or come back later to pick it up). Doing this will also tell you the condition of the battery.

There have been some issues with these vehicles where certain components of the vehicle will malfunction and drain the battery while the vehicle is off. First make sure the battery is good then make sure that it was your XM radio that drained the battery and not some other malfunctioning component on the vehicle. And if in your budget, it might be a good idea to purchase a battery charger in case something similar happens again because it sure is a pain the pull the battery out of one of these Xs.

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2010 Lexus RX350 still new
2003 BMW X5 3.0i w/sport package w/68K miles. (gone Thank God!)
2002 Dodge Ram 2500 4X4 cummins diesel w/198K miles, custom repo truck
2009 Scion tC w/46K miles
2007 Suzuki SV650 custom streetfighter
2000 Lexus GS400 w/165K miles