Disabling IBS (Intelligent Battery Sensor)

[Redd]

I've been battling increased battery discharge and weird voltage issues for a couple months now. I have a HUD device that reads voltage and I've been noticing voltage would randomly swing between 12.0V to 13.xV even with the engine running. When it's at the low end, battery would not charge properly and I've even gotten the increased battery discharge error once or twice.

Long story short, I've narrowed the problem down to a faulty IBS. Once I disconnected the IBS, voltage was a consistent 13.9-14.0V and never fluctuates. Battery charges perfectly, car is happier, even the a/c is a little cooler.

My question is this - Is it safe to run without IBS for long term?

I've been running without the IBS for a few days now and have not gotten any errors at all. Car is perfectly happy. Without the IBS, I know I will lose the following:

1. Battery charging logic for overcharge protection and to extend batt life - I'm already using a lithium batt, so the charge logic no longer applies to me. My batt also has a built in BMS that will protect it from overcharging.

2. Increased discharge errors to indicate potential alternator failure - I can monitor voltage which will give me early warning if the alternator has stopped working.

I'm wondering if I should replace the IBS or just run it without cos the consistent 14v is a lovely thing. Thoughts?

[spammysammich]

Might be alternator or voltage regulator. There seems to be some precedence for the voltage regulator going bad and being mistaken for a bad alternator.

[omgzirra_exe]

Originally Posted by Redd

I've been battling increased battery discharge and weird voltage issues for a couple months now. I have a HUD device that reads voltage and I've been noticing voltage would randomly swing between 12.0V to 13.xV even with the engine running. When it's at the low end, battery would not charge properly and I've even gotten the increased battery discharge error once or twice.

Long story short, I've narrowed the problem down to a faulty IBS. Once I disconnected the IBS, voltage was a consistent 13.9-14.0V and never fluctuates. Battery charges perfectly, car is happier, even the a/c is a little cooler.

My question is this - Is it safe to run without IBS for long term?

I've been running without the IBS for a few days now and have not gotten any errors at all. Car is perfectly happy. Without the IBS, I know I will lose the following:

1. Battery charging logic for overcharge protection and to extend batt life - I'm already using a lithium batt, so the charge logic no longer applies to me. My batt also has a built in BMS that will protect it from overcharging.

2. Increased discharge errors to indicate potential alternator failure - I can monitor voltage which will give me early warning if the alternator has stopped working.

I'm wondering if I should replace the IBS or just run it without cos the consistent 14v is a lovely thing. Thoughts?

coming from experience, due to not realizing the BMW tech did not plug my IBM in... DO NOT DO THIS.

I REPEAT DO NOT DO IT.

your battery will end up being overcharge the IBM prevents this and will BUBBLE. and will cause fluid to seep out of the battery. and will eventually cause a hazardous environment.

literally drove hard for 3 hours and NEARLY exploded my battery at the gas station.

[BPMSport]

Do not disable it. The IBS itself is often the issue - and sometimes the voltage regulator. When you replace it you'll likely need two adaptor cables as they changed the design. you should have an energy diagnosis performed and ensure the car is going to sleep by observing the start button illumination a few minutes after locking.

[Redd]

Originally Posted by BPMSport

Do not disable it. The IBS itself is often the issue - and sometimes the voltage regulator. When you replace it you'll likely need two adaptor cables as they changed the design. you should have an energy diagnosis performed and ensure the car is going to sleep by observing the start button illumination a few minutes after locking.

Can you elaborate on the two adaptor cables? When I searched for 'negative battery cable' it was only one part #, 61127616200.

[Redd]

Originally Posted by omgzirra_exe

coming from experience, due to not realizing the BMW tech did not plug my IBM in... DO NOT DO THIS.

I REPEAT DO NOT DO IT.

your battery will end up being overcharge the IBM prevents this and will BUBBLE. and will cause fluid to seep out of the battery. and will eventually cause a hazardous environment.

literally drove hard for 3 hours and NEARLY exploded my battery at the gas station.

This is interesting. Many cars using both lead-acid and AGM batts don't even have an IBS and let the batt see full 14.x v from the alternator with no issues. I shall monitor my batt closely and see if it heats up.

[akkando]

Originally Posted by Redd

This is interesting. Many cars using both lead-acid and AGM batts don't even have an IBS and let the batt see full 14.x v from the alternator with no issues. I shall monitor my batt closely and see if it heats up.

Your lithium battery at least shouldn't leak, bubble, or explode.

[Redd]

Just adding some additional info for future reference.

The E9x M3 IBS/negative battery cable is the same part # as other non-M E9x cars. However, not all E9x generation cars got IBS. Some 3er owners without iDrive say their cars did not come with an IBS. Seems to me the IBS is put into iDrive cars to prevent excessive discharge from certain accessories that may consume power even with the engine switched off.

That implies the battery should be fine without IBS. In fact, there have been cases of owners leaving IBS unplugged (accidentally) for over a year with no issues.

Below are some useful documents on purpose and detailed architecture of the IBS system. Some are linked from E6x group, but ours should be similar.

BMW e90 Voltage Supply & Bus Systems

BMW TIS - Intelligent Battery Sensor E60

BMW Power Systems - Energy Mgt

[Redd]

For the record, I will be replacing my IBS lol. But I may run it for a while with it disconnected just to test.

[omgzirra_exe]

Originally Posted by Redd

For the record, I will be replacing my IBS lol. But I may run it for a while with it disconnected just to test.

I'm just saying dude, try driving the car hard for an hour straight without it, the battery will, start to leak as the evac hose cant handle the pressure and will just pop off.

its going to smell rotten. lel

[DrFerry]

Originally Posted by omgzirra_exe

I'm just saying dude, try driving the car hard for an hour straight without it, the battery will, start to leak as the evac hose cant handle the pressure and will just pop off.

its going to smell rotten. lel

His battery is Lithium. There's no vapor outlet hose as far as I know with lithium batteries because there's no gel or fluid fill. I could be wrong but that's my understanding.

[Helmsman]

Originally Posted by Redd

This is interesting. Many cars using both lead-acid and AGM batts don't even have an IBS and let the batt see full 14.x v from the alternator with no issues. I shall monitor my batt closely and see if it heats up.

No immediate problem would be my assumption. Thought the IBS keeps track of current in/out over time to (to some extent) monitor health, I don't believe it directly is involved in controlling the regulator. Can't see how the battery can be cooked anyway, it accept the current it can and as long as the alternator/regulator doesn't start output a very high voltage toward the end of the charge cycle I can't see it happen.

[Redd]

Originally Posted by omgzirra_exe

I'm just saying dude, try driving the car hard for an hour straight without it, the battery will, start to leak as the evac hose cant handle the pressure and will just pop off.

its going to smell rotten. lel

Yeah I will definitely try this. For the sake of science lol

[omgzirra_exe]

Originally Posted by DrFerry

His battery is Lithium. There's no vapor outlet hose as far as I know with lithium batteries because there's no gel or fluid fill. I could be wrong but that's my understanding.

oh i had no idea what battert redd ran.

although i just wanted to share my experience with a oem bmw battery with ibm disconnected being the scariest thing to find out at a gas station LOL

[Redd]

Update - While running with IBS disconnected, I suddenly had DSC errors that looked like a bad wheel speed sensor. All 4 wheel speed sensors were replaced earlier this year. After restarting the car it went away after a few miles.

BUT... after pulling the codes, I saw a 'DSC overvoltage' error recorded. Looks like it's not a good idea to run with IBS disconnected.

I'll be installing the new IBS cable and plugging it back in.

[Redd]

The picture below is my original battery negative cable with IBS. They must have changed the part somewhere along the way cos the new cable I bought would not fit the original IBS adapter.

The complete IBS replacement kit is 3 parts:

61127616200 Battery negative cable with IBS
61129123571 Adapter lead IBS (connects to IBS plug)
12517615476 Adapter for IBS (connects between negative cable and IBS adapter lead)

[dpaul]

Originally Posted by Redd

Update - While running with IBS disconnected, I suddenly had DSC errors that looked like a bad wheel speed sensor. All 4 wheel speed sensors were replaced earlier this year. After restarting the car it went away after a few miles.

BUT... after pulling the codes, I saw a 'DSC overvoltage' error recorded. Looks like it's not a good idea to run with IBS disconnected.

I'll be installing the new IBS cable and plugging it back in.

IBS measures current drawn or supplied the battery, not voltage

The only way to get an overvoltage error is to have a bad voltage regulator.

Look, you've already done the homework yourself and know more about the functions of the IBS than many posters. As you have pointed out, and I can confirm, some e90s (FWIW it is those without navigation) come from the factory without IBS. It is clearly not necessary for proper engine operation including voltage regulation.

[djsilverjohnson]

Originally Posted by dpaul

IBS measures current drawn or supplied the battery, not voltage

The only way to get an overvoltage error is to have a bad voltage regulator.

Look, you've already done the homework yourself and know more about the functions of the IBS than many posters. As you have pointed out, and I can confirm, some e90s (FWIW it is those without navigation) come from the factory without IBS. It is clearly not necessary for proper engine operation including voltage regulation.

Does the E9x alternator even have a voltage regulator, or is like many modern cars where the engine computer controls the excitation voltage for the alternator?

[dpaul]

Originally Posted by djsilverjohnson

Does the E9x alternator even have a voltage regulator, or is like many modern cars where the engine computer controls the excitation voltage for the alternator?

Here's the part number for M3: 12317847517, ~$175 at FCP

However, this is probably one of those cases where I'd just throw a Rock Auto rebuilt $150 alternator in there.

[spammysammich]

Changing the voltage regulator requires removing the alternator anyway right?

[Redd]

Originally Posted by dpaul

IBS measures current drawn or supplied the battery, not voltage

The only way to get an overvoltage error is to have a bad voltage regulator.

Look, you've already done the homework yourself and know more about the functions of the IBS than many posters. As you have pointed out, and I can confirm, some e90s (FWIW it is those without navigation) come from the factory without IBS. It is clearly not necessary for proper engine operation including voltage regulation.

Good point. The new IBS has been installed. I will continue to monitor for DSC errors.

[mreverything]

Originally Posted by spammysammich

Changing the voltage regulator requires removing the alternator anyway right?

No it is connected to the back of the alternator where that black plastic cover is, super easy install 5 min