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Smart charging system

BMW has been using a smart charging system since the launch of the E65/66 7 series. The system works well and assists significantly with the diagnosis of the electrical system. In this post I will go through how the system works, components and what diagnoses can be done with the system.

Components of the System:

IBS (intelligent battery sensor)

The IBS sensor is small and built into the negative terminal on newer models. The E65/66 had a module called the, “power module” (PM) that monitored voltage use. The IBS will take measurements of battery voltage called, SOC (state of charge). This will also take a measurement called SOH (state of health of the battery).

2. DME (digital motor electronics)

The DME is the computer that controls the engine. The DME is the master for controlling the charging system.

3. Alternator

The component that generates electrical energy to power the vehicle and charge the battery. Some hybrid BMWs will not use an alternator since they use a start motor generator in place. I’ll get into that another time.

4. BSD (bit serial data line)

This is a communication line used for all these components to talk to each other. This is a single wire bus system, that without communication has 12v on the line and when communicating will have a digital square wave pattern.

It all comes together…

The IBS takes a reading of the battery voltage and SOH (state of health). Then, forward these reading over a BSD (bit serial data line) to the DME. The DME makes decisions on how to charge the battery from the reading of the IBS. Then, the DME sends out a command over the BSD to the alternator, for how much to charge the battery. The reason for this system is to save fuel economy. When an alternator is charging, it can put a huge drag on the engine. When charging the battery, it helps conserve fuel. In addition, the alternator is full-fielded during braking to provide a engine brake.

Another part of the smart charging system is energy diagnosis. This system monitors the vehicles battery when asleep and looks for draws on the battery. If the DME determines there is a draw from the IBS data, it will command a relay called 30F to switch off. This will turn power off to a majority of the consumers on the vehicle. The DME will use IBS readings to monitor the draw after the relay switch off. If the DME sees the draw is gone, the DME will keep the relay off until next key start up. Once the vehicle starts up, a warning will come up for high battery drain on the vehicle.

Using BMW software, you can run a test plan called, “energy diagnosis”. This will tell you the cause of high battery drain, charge history of the battery, parking time, history of trips and draw history. To start a test plan could tell you if the vehicle was woken up frequently. Meaning, the vehicle sleep mode was disturbed. That could be for multiple reasons; from a bad comfort access door handle, to a bad module waking the control module communication network. Energy diagnosis could also say the vehicle has a high parasitic draw and even tell you how long and how many amps the draw was. Energy diagnosis can also tell you if the vehicle was short tripped. Short tripping is when you drive the car less than the amount of time it takes to recharge the battery from initial start up. If this is done multiple times, the battery can be drained down. This can also determine if the battery drained because of the car being parked for a long time period. The software can also tell if the lights were left on. Software can also tell if the vehicle was used for a long period without the engine on. Finally, the vehicle can tell you when the battery is aged or faulty and requires replacement.

Replacing your Battery

The battery replacement does have to be the same AH rating and battery type. The DME charging strategy is based on those two items. If you install a battery of different AH rating and battery type the vehicle will not charge this properly and can shorten the life of the battery. BMW does give you options through the programming software to change the battery AH and type.
Once you replace your battery, you will have to register it to the vehicle. Registering is using another test plan to tell the DME that the battery has been replaced. The reason is, as the battery ages it will require more energy to recharge it. The DME takes this into account and will have the alternator charge the battery more as it ages. If you install a new battery and don’t register it, the DME will overcharge it and shorten the life span.

Thanks for reading and message me with questions!

The Lights Stay On

I have experienced a few models of BMWs where the lights are staying on — even when the car is shut off.

This will, of course, cause a drain and eventually damage the battery. Moving the light switch to the OFF position has no affect. This issue is apparent on multiple BMWs, but the main models it affects is the E65/66, and E60/61.

Normally there are no faults for this issue. I suggest to put the light switch into off and unplug the ride height sensors one at a time until the lights turn off. Whichever one you unplug and the lights turn off that is the one that has shorted and is causing the light module to crash.

Replacing the ride height sensor fixes the issue. Also, be aware that the E61 has air ride and will have 3 ride height sensors. Two on the rear and one on the right front lower control arm. Too many people replace light modules for this issue which is quite expensive in comparison to the cost of the ride height sensor.

Battery Care

Battery issues in BMWs have been a common complaint among many owners. The main issue in the past was a large sleep mode demand on the battery around 40 milli amps. Today’s battery demand in sleep mode is 22 milli amps, plus the amount of time it takes for the vehicle to get to sleep mode has been reduced in comparison to older vehicles.

With such a large demand in sleep mode it took a lot of energy to replace what was lost during sleep mode and when starting the vehicle back up. Let’s go through the different battery types and common issues that cause early battery failure or the dreaded battery charge low message. I will also describe what you can do to get the most life out of your battery.

BMW uses many different types of batteries including lead acid, AGM (absorbent glass mat), and lithium ion. Each of these types of batteries have different pros and cons.

Lead acid batteries

BMW no longer uses lead acid batteries regularly and AGM has become the standard.

-Pros: Lead acid batteries are inexpensive compared to the others. They can withstand harsh environments. They can be 100 recycled if properly done.

-Cons: they are heavy and have a short life span. Also, they self draw higher than the other two types of batteries.

2. AGM (absorbent glass mat batteries)

AGM is the most common battery in BMWs these days. Most of the new BMWs are using two batteries to assist with the electrical demand of the vehicle; especially when MSA (engine start stop system) is in use.

-Pros: longer life span, lighter weight. They also have low self discharge.

-Cons: more expensive and damaged easier when completely discharged.

3. Lithium ion

Lithium ion is the newest type of battery in BMWs. The use of Lithium ion started with the F80 M3.

-Pros: the lithium ion energy density is very high compared to the other batteries. They output of the battery is the same all the way until dead. They have the lowest self discharge rate. They will also hold a charge longer period of time.

-Cons: they are really expensive to replace. The charge rate is very specific, for example; using the wrong charger could damage the battery. The internal cells of the battery need to be monitored for temperature and charge for safety reason. If a lithium ion battery overheats it can ignite and would be very hard to extinguish.

These different batteries are marked on the case for what type they are. Once you determine what type of battery you have, then begin a care plan around the type. I witness my customer’s issues when they experience the battery discharged message in the car. There are multiple reasons this light appears. (For more, see my other post about energy diagnosis for lights turned on)

Below are other reasons why the battery drains:

Short tripping the vehicle

Short tripping the vehicle happens whenever the energy used to start the vehicle doesn’t get replaced. Basically, if you start the car and drive 1 or 2 miles to the grocery store and shut the vehicle off; the amount of energy to start the vehicle never was replaced properly. You can see how these short excursions can add up if this is all the vehicle is used for. Of course, this is magnified in colder weather when its typically harder to charge batteries.

2. Long vehicle immobilization

That is a very German description of letting a car sit too long. I see this often with vehicles that are stored or are rarely driven.

3. Weather

This is the biggest issue that accentuates the other two issues listed above . Where I am, in the midwest, during the Winter months the temps can drop into the negative degrees often. These harsh temperatures makes charging a battery back up much more difficult. If you have a lead acid battery, they can completely freeze and explode under certain conditions. Lithium ion and AGM batteries can’t charge/ discharge properly when super cold or overheated.

You’re probably wondering, what can I do to help keep my battery in the best shape and get the best life out of it?

The first thing to do is analyze how you use the vehicle. Does the vehicle get short tripped a lot? Is the vehicle a secondary vehicle that doesn’t get used much?

If the vehicle is short tripped a lot, you can take a long drive every so often to keep the battery up. The other option is to use a trickle charger. A trickle charger will maintain the battery by using the low and slow method. You will want to use a smart trickle charger that can sense the battery charge level and adjust its charge rate. This is the best method to help keep the battery at full charge. A trickle charger will not recharge a very low/dead battery. BMW actually has a very nice trickle charger kit now (The old brick looking one had major issues). The kit comes with two different hook ups. One is quick clips and a version that can be hard wired. Both of these have quick connectors to connect to the charger. DO NOT connect the trickle charger directly to the battery terminals on modern vehicle because you could damage the IBS (intelligent battery sensor). Instead, put the cables on the jump post under the hood. The BMW trickle charger has two settings: one for AGM and one for Lithium ion. The newer BMWs can have a AGM battery and a smaller Lithium ion battery. When charging a dual battery system, just set the trickle charger to AGM. The lithium ion battery has its own module that regulates voltage coming into the cells and can switch it self off once fully charged.

Another item to check is the age of the battery. BMW will stamp the manufacture date of the battery on the negative post. The top two numbers are the week the battery was produced and the bottom in the year (see picture below). Lead acid will normally last 4 years. AGM will last around 5-7 years. Lithium ion will set a faults when it is at end of life. If you are close to these timelines and trickle charging isn’t helping it may be time to replace the battery. ( If you are replacing a battery please read smart charging post about registering your battery)

BMW batteries are expensive and my hope is with better understanding of proper maintenance, BMW owners can avoid early and costly replacements.

Emoji Weirdness

Today’s cars are more advanced than ever. The problems have also became more advanced and complex. Many of you may have heard the new 2019 vehicles are coming with a new I drive system called, ID7.

With the new system many issues have arose with connected drive/ infotainment system. I recently worked on a new X7, and the owner had issues with Apple CarPlay connecting and disconnecting; or not reconnecting to the vehicle automatically. This only occurred with the spouse’s phone. BMW does have new software out to fix many issues with Apple CarPlay. I programmed the vehicle with latest software and tested it with my iPhone and CarPlay, and it operated properly.

I asked the customer to use their phone and it still wouldn’t connect properly. When given approval to search through the contact list, I found some of the contacts had emojis next to the letter names. This is important because, BMW head units can not interpret those emojis. Once we removed the emojis from the contacts the phone connected and worked perfectly.

I have encountered this on older models with bluetooth connection issues, but this was a first with CarPlay. Be aware there are plenty of kinks with new technology in BMW. More to come!

About the Guru

I have been a BMW technician for 10 years. I wanted to start a blog to help fellow BMW enthusiasts diagnosis their own vehicles and keep repair costs down. I believe you should be able to enjoy a BMW without breaking the wallet. In this blog I will discuss common BMW issues and repairs, new models, accessories, performance upgrades and anything that pops into my head BMW related.