HI all, 2006 650i convertible. Seems to have an intermittent issue with starting. The battery appears to be ok as car clock is staying on time and not falling out but when I have tried to start the car the engine would not crank over, implying insufficient amps. However, the engine then did crank over and start up the next morning. Very strange.

Has anyone experienced this and identified the source of the problem. It could be something simple e.g. I need to give battery terminals a good clean, they are tight on, or there is something else awry

Any thoughts/advice gratefully received.

Paul 

hi Paul.

how about a Dodgy sticking starter motor? 
@greydog mentioned somewhere about bad starters pulling too many amps and killing batteries. Not sure if it affects your model though? 

Could you try attaching your car to another running one with jump leads and try to start it? If it starts fine, then I would be inclined to say battery, but if not, I would look at the starter motor. 
 

Morning 

Magneti Starters there was an issue with them when they were starting to fail they would pull massive amps at cold start killing batteries. Several owners changed batteries when it was the starter at fault a guy with a 5 series not far from me had 2 batteries (one changed under warranty) I put a Clamp Ammeter on the starter cable and measured 940amps at cold start, 

So as Stu says get the starter checked but check all connections first and check the engine earth straps (seen a few of those) 

Of course if all those are OK more digging required

Dave

HI gents, great feedback as always. I have removed the battery terminals, cleaned and reattached them and have not had anything since, so far. I will get the starter checked though especially if it is a Magneti one.  

HI all, had another incident this morning. Warning came up on dash stating excess discharge. Clicking sound on starter for sure. Looks like the draw on the battery is the starter as reported and is around cold start and cranking amps 

To support this I have had the battery checked and all seems good with the battery. Only other thing I have seen before on other vehicles is battery discharge via the alternator but that seems to be an in use issue not a cold start one. Ill get the next service to identify the starter and see if it is a Magnetti as reported by Greydog. That should square the circle on this matter.