[MrSweet1991]

So, I got home a few days ago dropped my partner off and then went to head off but the car was dead, like you press the start button and the lights dim.. so straight away I buy another battery because the car was off the road for 15 months and to keep the alarm going I had to keep charging the battery and it would eventually die which is supposed to damage the cells and I was also under the impression if the alternator wasnt working the car would have gone into limp mode so with those two factors I purchased a new battery.

Again, car was fine and stopped off at a shop and this time same again lights dimmed out and cranked maybe twice (typical low battery symptom) so called my dad to get a jump start.. having waited 10 minutes I placed the fob into the car (its comfort access so fob usually in pocket) and this time it managed to slowly crank about 3 times just enough to start.. got home turned car off and back on again and it started okay, in secret menu alternator outputs about 13.7v idling and 14.2 driving.

With all of this information, what should I be looking at?

<--Update-->

Sitting in the car now about to head out and thought I would monitor voltage again, the screen is now showing 12.1/12.2 volts, accelerating does nothing.. either alternator or terminal issue? I'm just curious how I'm not in limp mode.

A further update, after my trip I noticed the voltage went slightly down while in a drive thru, it was now 11.9/11.8/12.0v.. I started to think I may get stuck in the drive thru Haha.. but yeah still confused. Car seems to be locking and flashing fine and car locked nice and quick as though battery is okay.

[rasa bmw]

has it been in for the battery cable recall ?

[MrSweet1991]

Originally Posted by rasa bmw

has it been in for the battery cable recall ?

No, I took it to BMW today for the blower motor recall but I've never had a recall in relation to the battery cable. I did come across a YouTube video where a chap replaced the entire length of the positive battery cable but beings as mine wasnt known for this recall I never paid to much attention. If i wanted to go down that route of checking, what exactly am I looking for?

[rasa bmw]

Originally Posted by MrSweet1991

No, I took it to BMW today for the blower motor recall but I've never had a recall in relation to the battery cable. I did come across a YouTube video where a chap replaced the entire length of the positive battery cable but beings as mine wasnt known for this recall I never paid to much attention. If i wanted to go down that route of checking, what exactly am I looking for?

ihad it done on my 06 330d but my 07 335d does not have the battery recall.i have seen videos on changing the cable etc,,,my 330d has felt like its cut out while driving once or twice,power down,,put clutch in and lights come on,,let clutch out and its going again,,thats been twice after the recall..strange one

[MrSweet1991]

Originally Posted by rasa bmw

ihad it done on my 06 330d but my 07 335d does not have the battery recall.i have seen videos on changing the cable etc,,,my 330d has felt like its cut out while driving once or twice,power down,,put clutch in and lights come on,,let clutch out and its going again,,thats been twice after the recall..strange one

Yeah, I looked into this more after you mentioned it but I don't have that issue. Where mine differs is I never have an actual power cut, it will just be a case if driving as normal, no warnings or power symptoms (radio still playing etc) but when I try to start the car all the lights dim as though the battery is too dead to output enough power, which may actually be the case but its finding out how it gets like that in the first place.

I've been monitoring voltages and while running its 14.1/14.3 and with ignition the battery appears very strong 13v slowly going down to like 12.9/12.7.. but there was the one occasion where the voltage while running was 12.1ish and the accelerator made no difference at all.. if it was positive side of things then surely, if it was random at making a connection I would experience power cut outs but mine can drive.. so I'm wondering if it's an occasional bad ground?.. the symptoms of a failing bad ground steal from engine mount to chassis/frame is slower cranks but mines really quick.. I seem to be doing circles when I try to narrow it down. Nonetheless I'm going to check every connection including those positive sides but it was raining yesterday so I had to stop.. I'll remove the rest of the boot liner later and then take out the fuse box side and then work on engine points.

[rasa bmw]

Originally Posted by MrSweet1991

Yeah, I looked into this more after you mentioned it but I don't have that issue. Where mine differs is I never have an actual power cut, it will just be a case if driving as normal, no warnings or power symptoms (radio still playing etc) but when I try to start the car all the lights dim as though the battery is too dead to output enough power, which may actually be the case but its finding out how it gets like that in the first place.

I've been monitoring voltages and while running its 14.1/14.3 and with ignition the battery appears very strong 13v slowly going down to like 12.9/12.7.. but there was the one occasion where the voltage while running was 12.1ish and the accelerator made no difference at all.. if it was positive side of things then surely, if it was random at making a connection I would experience power cut outs but mine can drive.. so I'm wondering if it's an occasional bad ground?.. the symptoms of a failing bad ground steal from engine mount to chassis/frame is slower cranks but mines really quick.. I seem to be doing circles when I try to narrow it down. Nonetheless I'm going to check every connection including those positive sides but it was raining yesterday so I had to stop.. I'll remove the rest of the boot liner later and then take out the fuse box side and then work on engine points.

ha ha i think im going loony link..happened yesterday twice,,same thing,,but it was me ha ha,,had cruise on at 32 mph in a restricted motorway zone,,then when it ended i put my foot down,,then when changed upto 4th gear,,it slowed quickly before i put foot downen into 5th,,clutch in and foot off gas,slowed again then it clicked in my loony noggin,,it was the cruise control,,,reverting to 32 mph as i never deactivated it,,always doing it in my cas now,,my old e46 any clutch press would deactivate it,,but on the later e series you have to switch it off or dab the brakes,,i hate it as i just forget,

[rasa bmw]

Originally Posted by MrSweet1991

Yeah, I looked into this more after you mentioned it but I don't have that issue. Where mine differs is I never have an actual power cut, it will just be a case if driving as normal, no warnings or power symptoms (radio still playing etc) but when I try to start the car all the lights dim as though the battery is too dead to output enough power, which may actually be the case but its finding out how it gets like that in the first place.

I've been monitoring voltages and while running its 14.1/14.3 and with ignition the battery appears very strong 13v slowly going down to like 12.9/12.7.. but there was the one occasion where the voltage while running was 12.1ish and the accelerator made no difference at all.. if it was positive side of things then surely, if it was random at making a connection I would experience power cut outs but mine can drive.. so I'm wondering if it's an occasional bad ground?.. the symptoms of a failing bad ground steal from engine mount to chassis/frame is slower cranks but mines really quick.. I seem to be doing circles when I try to narrow it down. Nonetheless I'm going to check every connection including those positive sides but it was raining yesterday so I had to stop.. I'll remove the rest of the boot liner later and then take out the fuse box side and then work on engine points.

i know you have probably looked,,but there are cases of the battery tray filling with water from poor rear light seals

[MrSweet1991]

Originally Posted by rasa bmw

i know you have probably looked,,but there are cases of the battery tray filling with water from poor rear light seals

Yeah, there was a case of water getting trapped at some stage but connections where pristine will upload video and pictures but as far as I'm concerned the rear is perfectly fine. I'm starting to think it's more of a ground strap issue possibly.. ice monitored voltages every journey and so far its output perfect voltages.. it really does only happen on rare occasions it seems