[nomiS330d]

About 6 months ago I was driving somewhere and my phone that was charging off the *** lighter starting charging then not charging intermittently. When I got where i was going I left the car for a few hours then when I got back to it it wouldn’t start so I jumped it using my noco booster thing. Everything was fine for a few weeks then it started doing it again every couple of journeys.
I did a lot of googling on it and found people saying the IBS could be faulty so I unplugged it which cured it…….or so I thought! Last week on my way to work I all of a sudden got loads of warning lights about abs and other items. I pulled over and the engine cut out! Then wouldn’t restart because the battery was completely flat. The rac came out and jump started it (my noco didn’t have enough power to start it). He checked the alternator was producing power which it was. I’m now using Carly to make sure it’s charging every time I go anywhere so I don’t get stranded. So far, it’s done it once more, not charging when I start it so I switch it off then restart and it then charges! Very weird!
Could it be that the alternator is gradually failing or could it be something to do with the electrics somewhere else? During all of this I’ve never once had the battery light come on the dash even when it’s not charging.
Sorry for the long winded post.

[therealdb1]

How old is the battery?
That's where I would look first.
Modern(ish) batteries fail in peculiar ways.
Simply measuring the voltage, even under a load, is not going to tell if it's serviceable or not and BMW's trick electronics are extremely susceptible to batteries that are not 100%.
I recently had to replace my 14 year old original battery. To the naked eye it looked fine but cranking was sluggish and all sorts of fault codes, airbag, abs, dsc, etc. would spring up each time I started the car. New battery - problem solved!
If your problems persist with a new battery it sounds like a dodgy connection, possibly because of a corroded earth, or IBS but to be fair you don't often hear of IBS causing trouble.
Has your car had the main power cable recall done?
Sorry my reply is as long winded as your question!

[nomiS330d]

Bosch battery is about 2 years old.
I’ve looked at all the wire connections, they all look fine.
I guess if the was a dodgy connection somewhere the problem would come and go when driving over bumpy roads. This problem is either there or not when the cat is started and will either be there or not until the engine is switched off then restarted.

[nomiS330d]

The battery isn’t an AGM. I didn’t know anything about that when I bought it. Still not sure how important that is.
My car hasn’t had a battery cable recall. It had the heater one which I had done. I’ll go check that the battery cable recall isn’t relevant to my car though.

[0l0dom0l0]

Did you code the battery to the car?

[therealdb1]

Originally Posted by nomiS330d

I guess if the was a dodgy connection somewhere the problem would come and go when driving over bumpy roads.

Not necessarily, if the dodginess is due to corrosion or oxidisation of the connection it would be consistently high resistance and not simply intermittent. The available voltage would then be dependent upon the load. This time of year you may have the lights, heater, rear screen heater, etc. all running which might cause IBS to shut down certain ancillaries like a cigarette lighter to conserve power.

Don't suppose your 2 year old battery is still under guarantee by any chance?

[therealdb1]

Originally Posted by 0l0dom0l0

Did you code the battery to the car?

This is very important especially if you changed to or from AGM to traditional lead acid. In 2 years with incorrect charging it could have killed the new battery.

[Chappers 71]

A 30minute drive or even a couple of hours drive won’t be enough to completely charge a flat battery, it will need two/three days on a charger to fully recharge it.
If you are not doing regular long journeys keep the car plugged into a trickle charger.

[nomiS330d]

Originally Posted by 0l0dom0l0

Did you code the battery to the car?

Yes.

[nomiS330d]

Originally Posted by Chappers 71

A 30minute drive or even a couple of hours drive won’t be enough to completely charge a flat battery, it will need two/three days on a charger to fully recharge it.
If you are not doing regular long journeys keep the car plugged into a trickle charger.

The weird thing is it always starts but doesn’t always charge. When I was driving it to work not realising it wasn’t charging so the battery went flat, when the rac got me going I drove the final 10 miles to work which was on Monday. I’m a lorry driver that stays out all week so on the Friday afternoon when I got back I fully expected the battery to be flat but it wasn’t, it started straight up! So I’m assuming the battery is alright. The issue is, it usually gets charged as normal but occasionally it doesn’t, very random.

[Chappers 71]

Originally Posted by nomiS330d

The weird thing is it always starts but doesn’t always charge. When I was driving it to work not realising it wasn’t charging so the battery went flat, when the rac got me going I drove the final 10 miles to work which was on Monday. I’m a lorry driver that stays out all week so on the Friday afternoon when I got back I fully expected the battery to be flat but it wasn’t, it started straight up! So I’m assuming the battery is alright. The issue is, it usually gets charged as normal but occasionally it doesn’t, very random.

Mine always started no problem even though its only usually driven once a week. I had it plugged in for a diagnostic & low battery warning came up & then had to jump start it, had previously driven it for 40 minutes or so. Got home after a further 15 minute drive & car started up no issues next day.
Took it to my local battery shop, he checked battery & all was good other than the machine saying it needed charging. I was then told to put it on a trickle charger for 2 or 3 days as the cars alternator won't fully charge a completely flat battery.

[therealdb1]

Don't forget these cars consume a fair bit from the battery when not being driven. I sat in my car for an hour following a half hour drive the other day and I could hear the HDD running, heater flaps moving up and down and all sorts of whirring and buzzing which probably discharged all that I had put into the battery while the engine was running.
I guess that's why they need IBS
Because mine is a second car I always put it on trickle charge between drives and even then it can take a couple of days for the charger to register "full battery".

[nomiS330d]

I’ll give that a go next weekend then. Thanks.