E46 - Battery died all of a sudden

[JaFool1]

I'm hoping this is a case of an old battery finally giving up and not a parasitic drain....

Yesterday I took my 330i out around midday. I was driving for around 30 mins total with around 4 stops (engine off). There was no sign of any battery issues at all.

I jumped back in later in the evening - flicked the ignition to 1, wound both front windows down with no issue, Flicked the ignition to 2 and everything went dead. No dash lights, interior lights, windows, nothing. After leaving it for a few hours one of the interior lights and airbag light began to flicker when ignition turned to 1.

We tried to jump start it for around 20 mins but no joy. All the electrics come on when cables connected up but as soon they are disconnected everything goes completely dead again. A multimeter gives a reading of 5.5V

Has anyone experienced anything similar? Is just a standard dead battery or is there something draining it?

[Johnnytheboy]

In my experience of more modern vehicles (by which I include E46's), when the battery goes it often goes terminally with no warning.

[Locknut]

The same thing happened to me with a Nissan a few years ago. I started up at my house and drove about a mile to the shops. I parked up and went into the shop. I came out a few minutes later and when I tried to start the car the battery was dead.

[d_a_n1979]

Yup, new battery but check the FSU hasn’t failed, common battery drain...

Get the biggest battery you can for the car, like the E39, the M54 engine wasn’t a decent battery, so the Bosch S4 019 at minimum, if the S5 019/ Yuasa 019 are ideal (if they’ll fit in the battery compartment)

Voltage should be c12.4v at engine off and c14.4v with engine idling...

[anonymous-user]

I used to have the same issue with an E46. The battery would work fine for a week or so and then suddenly I would get a click and nothing would happen. I was convinced it was parasitic drain so I used to always carry another battery and swap them over, charging the other when I got home. It was so annoying I was looking at buying the cheapest brand new car I could just so I didn't have the issue anymore.

Tested the battery with a voltmeter and nothing was wrong at all.

It happened one day at my dads and I had forgotten to charge my second battery so he found one in his garage and fitted it. I never had the issue again, I must have had two defective batteries.

If I were you I would fit a known good battery as this may well solve the problem.

[JaFool1]

UPDATE

After unscrewing the negative connector on the existing battery and resting it ontop of the terminal all the lights in the car came back on. I connected it back up and the car started first time. 14.4V whilst engine running and 12.5V when engine is off.

What on earth? Is there some sort of overload protection that was reset when disconnecting the battery?

I'm going to keep the new battery in the boot for the next few days just in case...

[cossy400]

Wire wool the battery posts. could just be they 've furred up and lost a good connection.

of all you 've done is rested the wire on the terminal start with the simple stuff

[E-bmw]

JaFool1 said:

What on earth? Is there some sort of overload protection that was reset when disconnecting the battery?

No, you have just found the dodgy connection that was causing the problem.

[d_a_n1979]

As others have said, cacked up connections. Clean them and it’ll be fine...

[Zener]

cossy400 said:

Wire wool the battery posts. could just be they 've furred up and lost a good connection.

of all you 've done is rested the wire on the terminal start with the simple stuff

This ^ and no the E46 dont have a reset strategy in place , good battery post connection is paramount if you dont want to spike various electrical modules fitted to the car inc the ECU/DME you had your warning already