Battery disconnected at 120mph!

lenabos · 02-04-2023, 01:25 PM

Probably my scariest moment behind the wheel.

I had my new Android Headunit delivered today so i went about installing it. I disconnected the minus clamp on the battery, took the trim pieces off, disconnected the everything, connected the new unit. At this point, i didn't put everything back in and trim back on because i wanted to check it was working. I put the clamp back on the minus node without tightening the nut, went back to check the unit and its working perfect! Due to the excitement of the headunit working i COMPLETELY FORGOT TO RETIGHTEN THE NUT!! Closed the boot, put the trim pieces back on and went about my day.

Fast forward 1 hour, i'm doing 120mph on mexico's M25 motorway (was empty at the time), attempt to make a lane change and all of sudden no power, power steering fails, all of the dials turn off and go to zero and head unit turns off. Mind you engine was still running. About 5 seconds later, the screen comes back on, dials show the indicated speed/revs and then a few of warning lights: Chassis stabilisation ABS light, different lock limited and another saying the something about the battery is compromised. By the time i had processed everything, my speed had dropped to 40mph, so i kept it 40mph all the way to the next service in absolute silence. Through out the drive i'm thinking "did my crank hub spin?" even though engine was running smooth as can be. First thought for any S55 owner when somethings goes wrong lol.

Got to the service station, parked, turn the engine off and literally all power died. It was at this point i realised my mistake. I tried opening the boot, i couldn't because there is no power. tried putting the rear seats down from the back seat, but the latches are in the boot (great design BMW). I ended up getting someone to give me a jump start to allow me to open the boot and as expected, the minus clamp is nowhere to be seen. I put it back on the node, tightened the living F*** out of it, started back up and now drives as if nothing happened.

I read somewhere that battery disconnecting while driving can cause irreparable damage to the electronics. i consider myself extremely lucky and want to thank BMW for making their cars moron-proof.

slaughter.mode · 02-05-2023, 06:15 AM

This actually happened to me not long ago after I swapped my motor. Imagine how that felt after waiting a few months of being without the car just to have that happen. I was driving in LA traffic, too. Southern Californians cannot drive. First the dash went black for a few seconds then all sorts of DME codes were popping up; aux coolant pump failing, turbocharger coolant pump signal, etc. Car ran pretty normally though, was even blasting music with Apple Carplay although it was 'skipping' quite a bit which it never does. I usually blame that on my iPhone. I finally pull over to a gas station to turn it off then back on again and nope-dead. My dumbass didn't think to consider it was the battery until that moment. Once I got a spark under the hood I popped the trunk and the negative was off the terminal. Re-installed it and never saw any of those DME codes again.

lenabos · 02-07-2023, 02:14 AM

Quote:

Originally Posted by Corn Mode

This actually happened to me not long ago after I swapped my motor. Imagine how that felt after waiting a few months of being without the car just to have that happen. I was driving in LA traffic, too. Southern Californians cannot drive. First the dash went black for a few seconds then all sorts of DME codes were popping up; aux coolant pump failing, turbocharger coolant pump signal, etc. Car ran pretty normally though, was even blasting music with Apple Carplay although it was 'skipping' quite a bit which it never does. I usually blame that on my iPhone. I finally pull over to a gas station to turn it off then back on again and nope-dead. My dumbass didn't think to consider it was the battery until that moment. Once I got a spark under the hood I popped the trunk and the negative was off the terminal. Re-installed it and never saw any of those DME codes again.

Literally the exact same, just imagine it at 120mph! It's scary when the steering seizes and brakes start to spaz out.

i've learnt my lessons but i now keep atleast one of my back seats permanently unlatched in the case i need to access the boot when power is down. i know i can give it jump with the (+) and earth in the engine bay but just to save the hassle.

Psychotic Mouse · 02-07-2023, 06:10 AM

The rear boot issue is a pain in the ass. I have a faulty rear ECU so can’t open the boot at all. I had to use a golf club and a coat hanger between the seats After losening some bolts.

What i have done now as a back up is I have tied a Strong string to the emergency release handle in tje boot and ran it to the back seat. This way ypu can access the boot still amd keep the seats latched.

02-04-2023, 01:25 PM	#1
lenabos Enlisted Member 10 Rep 31 Posts Drives: 2015 BMW M4 (F82) Join Date: Apr 2021 Location: Bedfordshire, UK iTrader: (0) Garage List 2015 BMW M4 [0.00]	Battery disconnected at 120mph! Probably my scariest moment behind the wheel. I had my new Android Headunit delivered today so i went about installing it. I disconnected the minus clamp on the battery, took the trim pieces off, disconnected the everything, connected the new unit. At this point, i didn't put everything back in and trim back on because i wanted to check it was working. I put the clamp back on the minus node without tightening the nut, went back to check the unit and its working perfect! Due to the excitement of the headunit working i COMPLETELY FORGOT TO RETIGHTEN THE NUT!! Closed the boot, put the trim pieces back on and went about my day. Fast forward 1 hour, i'm doing 120mph on mexico's M25 motorway (was empty at the time), attempt to make a lane change and all of sudden no power, power steering fails, all of the dials turn off and go to zero and head unit turns off. Mind you engine was still running. About 5 seconds later, the screen comes back on, dials show the indicated speed/revs and then a few of warning lights: Chassis stabilisation ABS light, different lock limited and another saying the something about the battery is compromised. By the time i had processed everything, my speed had dropped to 40mph, so i kept it 40mph all the way to the next service in absolute silence. Through out the drive i'm thinking "did my crank hub spin?" even though engine was running smooth as can be. First thought for any S55 owner when somethings goes wrong lol. Got to the service station, parked, turn the engine off and literally all power died. It was at this point i realised my mistake. I tried opening the boot, i couldn't because there is no power. tried putting the rear seats down from the back seat, but the latches are in the boot (great design BMW). I ended up getting someone to give me a jump start to allow me to open the boot and as expected, the minus clamp is nowhere to be seen. I put it back on the node, tightened the living F*** out of it, started back up and now drives as if nothing happened. I read somewhere that battery disconnecting while driving can cause irreparable damage to the electronics. i consider myself extremely lucky and want to thank BMW for making their cars moron-proof.
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02-05-2023, 06:15 AM	#2
slaughter.mode Major 881 Rep 1,044 Posts Drives: 2018 M4 Competition Join Date: Mar 2018 Location: Chino Hills, California iTrader: (0) Garage List 2018 BMW M4 ZCP [9.80]	This actually happened to me not long ago after I swapped my motor. Imagine how that felt after waiting a few months of being without the car just to have that happen. I was driving in LA traffic, too. Southern Californians cannot drive. First the dash went black for a few seconds then all sorts of DME codes were popping up; aux coolant pump failing, turbocharger coolant pump signal, etc. Car ran pretty normally though, was even blasting music with Apple Carplay although it was 'skipping' quite a bit which it never does. I usually blame that on my iPhone. I finally pull over to a gas station to turn it off then back on again and nope-dead. My dumbass didn't think to consider it was the battery until that moment. Once I got a spark under the hood I popped the trunk and the negative was off the terminal. Re-installed it and never saw any of those DME codes again. __________________ Instagram: Slaughter.Mode
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02-07-2023, 06:10 AM	#4
Psychotic Mouse Private 88 Rep 99 Posts Drives: Sakhir Orange M3 Join Date: Nov 2017 Location: Pretoria South Africa iTrader: (0)	The rear boot issue is a pain in the ass. I have a faulty rear ECU so can’t open the boot at all. I had to use a golf club and a coat hanger between the seats After losening some bolts. What i have done now as a back up is I have tied a Strong string to the emergency release handle in tje boot and ran it to the back seat. This way ypu can access the boot still amd keep the seats latched.
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