Yes, a low battery will crash a nav. Try putting the car on a high amperage charger while you do the test or do the test with the engine running. Most likely, it will be fine. Your problem is likely either a low battery or a failing battery.

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2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input