Why does a replacement battery in the i3 need to be registered??

This is the information I read from the Facebook group "BMW i3 enthusiast"

"There is no electronics in the battery. You do not need to 'register' the battery. It does NOTHING. And your car can't tell the difference between ANY 12v agm (glass mat, gel cell, motorcycle) battery. Of any size. Save your money."

Can someone explain why BMW, and from what I read other German car manufacturers, require that you to register your replacement battery into the software of the i3's computer. I would like an explanation. Not just cause it says so but some logical reasoning that they require this process.

I know there are tools that allow you to perform this task after battery replacement but they cost >$200. (foxwell NT530 model and others).

I'm on the "no" camp on this one.

It's just a simple AGM battery with no special needs, nor a flat discharge curve that requires programming to calculate a charge profile.

If this battery registration was worth anything, the car would warn us before the 12v suddenly dies.

There are posts on BMW forms claiming company memos state the registration process is for QC tracking purposes only.

I haven't seen these memos, but I also haven't seen anyone produce hard data as to what parameters are being monitored or modified.

Audi the same. I skipped registration by keeping my allroad alive on a 12v charger. Car didn't miss a beat for the next couple of years I owned it. Many BMW owners report the same.

This is the information I found with a simple Google search....


Q: Why do I need to register a new battery?
A: The short answer is that BMW designed the charging system with an algorithm that varies the rate of charge by the age and type of the battery installed. Registering a new battery resets the algorithm back to optimal charging voltage for the specified battery.

If the battery is failing after 3-4 years using BMW's optimal charging algorithm, I'd roll the dice on not registering the replacement just to see if it lasts longer.....

vreihen said:

If the battery is failing after 3-4 years using BMW's optimal charging algorithm, I'd roll the dice on not registering the replacement just to see if it lasts longer.....

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Our 12 V battery is 5.5 years old and functioning normally. I don't think we know why some i3 batteries are failing early. I suspect that some i3's sat on dealer lots for several months unsold whereas ours did not. If their 12 V batteries weren't charged periodically, they could have discharged so far that their lives were shortened such that even an optimal charging algorithm as a result of registration could not made their life expectancies normal.

However, I doubt that the cost of registration or purchasing an OBD scanner that can register a 12 V battery would be recovered by the savings of less frequent 12 V battery replacement as a result of an increased 12 V battery life. Nevertheless, I bought a Foxwell NT520 Pro scanner with BMW software preinstalled ($160 at Amazon) that can register a new identical 12 V battery when the time comes and that can read and clear BMW-specific Diagnostic Trouble Codes (DTC's).

eNate said:

It's just a simple AGM battery with no special needs, nor a flat discharge curve that requires programming to calculate a charge profile.

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The ideal charging algorithm of an AGM battery differs from that of a flooded-cell or gel battery. However, the replacement battery is also an AGM battery like the original, so the charging algorithm would be the same. The difference could be that this algorithm adjusts for a battery's age, the number of charge-discharge cycles that I believe are recorded, the measured battery capacity, etc. It could not adjust for some of this if a new battery were not registered.

eNate said:

If this battery registration was worth anything, the car would warn us before the 12v suddenly dies.

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A 12 V battery can fail when a sudden internal short circuit occurs which cannot be predicted. I don't think it's possible to predict the death of an AGM battery unless a slow, steady decline is occurring, maybe due to increasing internal resistance or decreasing capacity. Some i3 owners have seen a message that indicates a weak and failing 12 V battery, but most haven't. Maybe registration and the related monitoring of the 12 V battery can warn of 12 V battery failure and display a message in certain but not all circumstances.

eNate said:

There are posts on BMW forms claiming company memos state the registration process is for QC tracking purposes only.

I haven't seen these memos, but I also haven't seen anyone produce hard data as to what parameters are being monitored or modified.

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It would be nice if manufacturers that support battery registration would explain in detail what's happening. I'm not jaded enough to believe that BMW dealers would charge its vehicle owners for battery registration that is benefitting only BMW.

eNate said:

Audi the same. I skipped registration by keeping my allroad alive on a 12v charger. Car didn't miss a beat for the next couple of years I owned it. Many BMW owners report the same.

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Well, maybe such intervention wouldn't have been necessary to such an extent had you registered your new battery. Unfortunately, we're all just conjecturing at this point.

From BimmerScan: "The registration of the battery replacement is required to inform the power management (software in engine electronics and intelligent battery sensor) that a new battery was installed in the vehicle. If the battery replacement is not registered, the power management will not function properly and can lead to functions being limited by individual electrical consumers being switched off or having their power consumption reduced. Power management will charge the new battery as if it’s the old worn out battery, causing premature failure of the replacement battery."

The intelligent battery sensor is the red blocky module at the negative battery terminal connection.

My understanding is that the ECM power management software uses an algorithm that counts the number of charge cycles and adjusts the charge frequency and duration to the 'age' (number of charge cycles) the battery has experienced - with the algorithm based on cycle/aging data supplied by the battery manufacturers. Failing to register the battery means that the charge-cycle counter has not been reset, so the power management software is still charging the new battery as an 'aged' battery, which means over-charging it. This can lead to premature failure, and supposedly can cause issues in the electronics being supplied power from the battery.

MKH said:

From BimmerScan: ... <snip>

...the charge-cycle counter has not been reset, so the power management software is still charging the new battery as an 'aged' battery, which means over-charging it. This can lead to premature failure, and supposedly can cause issues in the electronics being supplied power from the battery.

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This is where I think this all falls apart.

For starters, so much of the "pro registration" argument online comes from companies trying to sell something, such as BimmerScan, with a dearth of info directly from the source.

But more importantly, what "aged battery" takes a higher (more stressful) rate of charge than it did when new? Generally speaking, batteries have lower capacities, produce decreased voltages, and develop higher internal resistance as they age. In other words, if it was really an intelligent charging circuit, it might decrease the charging current and voltage, but I can't imagine a scenario where it would "turn it up to 11."

Now, I understand BMW and Mercedes are switching some of their higher-end models to Lithium Ion 12v batteries. Li-Ion is trickier because they exhibit a very flat discharge curve that requires more advanced technology to charge and maintain. But even this is well understood and replaceable Li-Ion batteries are a common feature in numerous consumer products, without resorting to "registration" when a new battery is installed.

AGM is a step away from traditional lead-acid, and because they're sealed they need to be charged carefully (can't just apply a standard-rate current and forget about it). But this is a mature technology that's been in use since decades.

If I had to suppose anything, it might be that registration is simply a step to ensure the user is replacing a like-for-like battery, i.e. NOT accidentally bolting in a lead-acid battery. Or maybe the system can adapt between lead acid and AGM, and registration would inform the charging system how to handle the new battery type.

I would LOVE to see some technical documentation from BMW.

Or maybe the system can adapt between lead acid and AGM, and registration would inform the charging system how to handle the new battery type

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When the battery is registered, during the registration process (if changing types of battery) you select AGM or Lead Acid, and what the amperage of the new battery is.

See the process starting at 2:20 in the video:

https://www.youtube.com/watch?v=ioExRnpMyqg

You may not have as much of an issue if the battery is the same type and size. But, should you decide to change either, it is likely that the life of the new battery will be decreased.

The 'coding' process is pretty simple with the proper tools. Pep Boys will do it for you for around $25, the dealer will charge you LOTS more.

By knowing its size, the car can determine approximately how long it can go before recharging, and how aggressively it can apply power. Keep in mind, many of today's modern cars never fully go to sleep...some of the computers and various accessories are actually constantly running. By knowing the type and size, the car can make an estimate of what it can leave on and for how long. If you don't use the car for a longer period of time, you might notice a message that it went into low power mode to try to save the battery. An AGM can usually handle a lower voltage better than a flooded cell, but also prefers a different charge curve. Batteries like the 12vdc one in your car are constantly degrading. How far it gets discharged and how often are a big part of it, as is the ultimate charge voltage level and charging rate.

So, yes, you can ignore resetting the life monitor, and probably the type, but if you were to change the size, you'd have a bigger problem. Say the new one is smaller, the car would think it could run things longer and still not damage it, making it fail sooner. An older battery can take longer to recharge fully since the internal connections have more resistance. Knowing this, can affect how fast and how completely the battery gets charged when you have some smarts applied. The ultimate full charge voltage differs slightly between AGM and flooded cell. That's why the better battery chargers and tenders have an AGM setting...the battery lasts longer. So, telling the car exactly what's in there makes sense, at least to me. Apparently, BMW thinks so, too, otherwise, they wouldn't include the logic to optimize things. Why bother with the complexity and end cost?

I'll give BMW credit for this: With my Audi, I needed a BEM code (basically a serial number) to register the new battery. And the system is "smart enough" to reject me re-entering the original battery's BEM, but accepts somebody else's BEM that's been posted online and passed around a dozen times like a software key for a 1980's video game (we're talking the allroad here -- there weren't that many of us!!).

So that BMW gives the user the option to enter the battery info directly, rather than require a serial number, that's at least a little more user friendly, and deserves a kudos.

FWIW, if you buy a BMW branded battery, there's a bar code on it, and all they have to do is scan it to register it...the code tells everything needed to ensure the charging circuit knows what battery is in there. But, you have to have their computer system attached to the car for it to work. There is also the coding way, where you can manually enter the requisite values. It would be nice if the car's user interface would let you do it without special tools, but BMW is not really into the user doing this sort of maintenance themselves. Without the service group, most car dealers wouldn't be profitable...they rely on the cars coming in for service. That price is built into the vehicle, and corporate doles out some of it back to the dealers when that service is actually performed...the rest, the customer has to come up with, especially after the warranty expires!