Dead 2004 X5 4.8is...

[Roadhouse]

Hey all,

Got an annoying issue with my ride - she's dead as a doornail... It's a 2004 4.8is, in otherwise immaculate condition.

First happened a few days ago - unlocked the car, jumped in and went to crank it over and it died. Zero lights inside, but had 1 headlight on!

Anyway wouldn't crank at all so called the roadside service company and they connected up their battery jumpstarter and started perfectly. He tested the battery and it had 92% charge after about a minute of running. Also did a load test and passed fine. Had him baffled...

Anyway, no issues for the past 5 days since, then same thing happened today - dead as a doornail.

Any suggestions? Could it be the battery, even though it tested fine, or could it be an electrical gremlin lurking somewhere? Seems strange to be fine one minute, dead the next, then fine again (for a while) the next...

Had anyone had a similar issue and if so, what was the fix?? What other areas other than the battery should I be looking at?

Many thanks
Simon