[k9vdimmest]

I recently purchased a 2016 BMW 320i F30 LCI (with the b48), I noticed that whenever I would start the car it would struggle for a second then turn on completely fine. As I hadn't driven it much I initially chalked that up to the car starting rough as it was cold, but then, even after the car would warm up it would still take a second to start.

I installed a dash-cam with a hardwire kit, this dash-cam's hardwire kit allows the user to tell the dash-cam to turn off if the battery's voltage is below 11.8v (which is the lowest voltage setting). This would in theory with a good battery, allow the dash-cam to run for at least 24 hours before it having to shut off. Instead, my camera would shut off within 30 minutes of the cars ignition being turned off.

I grabbed my scanning tool and checked the voltage of the battery through the OBD port and the battery voltage read 12.4v with the engine off (granted I did move the car into the driveway moments prior). However, when I started the car, the battery voltage dropped to 7.75v and once the alternator started to charge the battery it went back up to 14.2v on average.

I've read online that this isn't normal and it's a sign that one of the battery's cells is dying if not completely dead, which would (in my assumption) explain the poor startup and dash-cam shutting off.

Has anyone else experienced the same symptoms and has replacing the battery worked for them?

[alohasurftoad]

Time for a new battery

[Billfitz]

Dropping to 7.75v isn't normal, but it doesn't necessarily mean the battery is bad. There are a number of possible explanations, including but not limited to a bad cable to the starter, loose or corroded cable connections, or a deteriorated engine ground strap. The dash cam may be turning off because the circuit you wired it to is turning off on command of the power management system, which in many cases is due to time rather than voltage. One way to test the camera situation is to hook up a charger to the under hood posts before it shuts down. If it still shuts down it's a time related shut down. Changing the battery may be the answer, but it may not. You wouldn't be the first by any means to accept advise to change the battery to find out that it made no difference. If your Sydney is in Oz (you should make that clear) I'd be looking at the corrosion issues. Salt sea air isn't copper friendly.

Edit: take a look at this, specifically the edit just made today. https://f30.bimmerpost.com/forums/sh....php?t=2078396

[k9vdimmest]

Originally Posted by Billfitz

Dropping to 7.75v isn't normal, but it doesn't necessarily mean the battery is bad. There are a number of possible explanations, including but not limited to a bad cable to the starter, loose or corroded cable connections, or a deteriorated engine ground strap. The dash cam may be turning off because the circuit you wired it to is turning off on command of the power management system, which in many cases is due to time rather than voltage. One way to test the camera situation is to hook up a charger to the under hood posts before it shuts down. If it still shuts down it's a time related shut down. Changing the battery may be the answer, but it may not. You wouldn't be the first by any means to accept advise to change the battery to find out that it made no difference. If your Sydney is in Oz (you should make that clear) I'd be looking at the corrosion issues. Salt sea air isn't copper friendly.

Edit: take a look at this, specifically the edit just made today. https://f30.bimmerpost.com/forums/sh....php?t=2078396

Thanks for all the help, I'm located in Sydney so I'll have a look around today and see if there is any corrosion. I'll also see if I can hook up a battery charger to the battery and see if the car starts up better

[Billfitz]

If you can get your hands on a high capacity auxiliary battery or charger or even another car hook it up to your under hood posts and see what happens to the voltage when you start the car. If it still dips below 11v you know that something is causing a major current draw.

[k9vdimmest]

Originally Posted by Billfitz

If you can get your hands on a high capacity auxiliary battery or charger or even another car hook it up to your under hood posts and see what happens to the voltage when you start the car. If it still dips below 11v you know that something is causing a major current draw.

I just had a look around the car and I couldn't see any corrosion. Nothing around the battery, fuse boxes etc, as It's been raining here in Sydney I haven't been able to go under the car. I'm going to attempt to hook up another car to the hood posts.

What voltage should I get the battery to before attempting to start?

I'll have my scanning tool connected so it can give me a reading of the lowest voltage.

[k9vdimmest]

Originally Posted by Billfitz

If you can get your hands on a high capacity auxiliary battery or charger or even another car hook it up to your under hood posts and see what happens to the voltage when you start the car. If it still dips below 11v you know that something is causing a major current draw.

Ok I've got some results:

I left the car for 6 hours and before leaving it I checked the battery voltage and it was at 12.5v. After 6 hours the voltage was still at 12.5v so the battery is probably ok.

I connected another car to the 320i's hood post and let the other car charge the 320i's battery for a little while. at 13v I started the car and it did the same split second weak crank and the battery voltage dropped to 8.3v. So hooking up another car didn't help.

the only way I was able to get a clean crank was when I started the car, the 320i's alternator charged the battery to 14.2v, I turned off the car and when the cars battery instantly dropped to 13.5v I started the car up again (it was still cold) and the car had a MUCH stronger crank and the battery didn't drop past the previous 8.3v low.

I also noticed that when the car was turned off (with nothing charging the battery) the batteries voltage spikes down to 12v from 12.5v then levels out at 12.5v. This could be causing my dash-cam to be shutting off idk if its related to the dash-cam but I might disconnect the dash-cam and see if the spike down occurs.

I'm thinking it may be a corroded engine ground.

(P.S when the 320i's battery cranks on its own it consistently drops to 7.75v everytime)

[Billfitz]

I'd say that's definitive, something is eating up current big time. It could even be the starter, but being cheap and easy to replace I'd start with the ground strap.

[Awdbrandon]

I just replaced the ground strap near my downpipe on my 13' 335i.
Caused a no crank no start, but most importantly, I noticed that the voltage would drop DRASTICALLY as the ignition was switched.

[Billfitz]

A bad ground strap can be dangerous too. If it's sucking up enough current to prevent the car from starting that current may be heating the strap to the point that it could cause a fire. It would be rare, there shouldn't be anything flammable close to it, but it's not out of the question.

[k9vdimmest]

Originally Posted by Billfitz

A bad ground strap can be dangerous too. If it's sucking up enough current to prevent the car from starting that current may be heating the strap to the point that it could cause a fire. It would be rare, there shouldn't be anything flammable close to it, but it's not out of the question.

Just had a look at the ground strap using a small camera and It doesn’t seem like there is any corrosion, you have a look and let me know what you think. I also don’t think the starter is the issue because when the start/stop is on, the car turns on instantly the moment I put my foot on the break.

I don’t know how to upload photos

[Billfitz]

The car will start more easily when it's warmed up, so that doesn't necessarily mean anything. The ground strap may be fine, I just brought it up as being one of the possible issues. Another possibility is the starter bearings are going. When the starter is cold they're tight, loosening up when the engine warms. It could even be the battery. If you have a car to jump with, and robust jumper cables, see what happens when you disconnect the negative terminal of your battery, starting the car only with the jump from the other car.

[k9vdimmest]

Originally Posted by Billfitz

The car will start more easily when it's warmed up, so that doesn't necessarily mean anything. The ground strap may be fine, I just brought it up as being one of the possible issues. Another possibility is the starter bearings are going. When the starter is cold they're tight, loosening up when the engine warms. It could even be the battery. If you have a car to jump with, and robust jumper cables, see what happens when you disconnect the negative terminal of your battery, starting the car only with the jump from the other car.

I'll try and give that a go, I also noticed that when I got into the car and put my foot on the break pedal the voltage went from 12.5v to 11.9v without touching anything but the break pedal but thats most likely just electronics booting up.

Is there any way to test the starter, maybe heat the starter up to loosen up the bearings?

[Billfitz]

A quick drop in voltage isn't unusual, as you say lots of stuff is firing up, including the fuel pump. You can test the starter but you have to pull it to test it. The starter solenoid is another possibility. For that matter the possibilities are almost endless. Read this post all the way through: https://f30.bimmerpost.com/forums/sh....php?t=2071505

[Billfitz]

I came across this last night, the symptoms are very close to yours. He found a loose connection at the battery, but a loose connection anywhere from there to the starter would have the same effect.

[k9vdimmest]

Originally Posted by Billfitz

I came across this last night, the symptoms are very close to yours. He found a loose connection at the battery, but a loose connection anywhere from there to the starter would have the same effect.

Thanks for all the suggestions, I've had no time to work on the car but I've got a spare battery from an x5 that I may be able to use and see whether it is the battery thats causing the issues

[k9vdimmest]

UPDATE:

It ended up being the battery...

but like in the previous messages, it could've been anything. What made me replace the battery was sometimes when I would start the car at night (with headlights on) the entire dashboard would shut off for about 1-2 seconds then it would start cranking. On top of that, the cars sensors (Parking sensors, Crash sensors, Pedestrian sensors, etc) would fail and come up as an error code on the idrive system, then after driving for a little bit they would go away.

I found a brand new battery at the dealership for $680 AUD and I replaced it and it's literally better than when I bought the car.