I routinely visit several different marque and model forums as part of the leisurely process of deciding on a replacement for my current car. These fourms all share a common characteristic: very lengthy thread or threads on the topic of replacing the (12 V main) battery. I think it is fair to say, based on content, that the genesis of a high level of interest in this topic is to avoid outrageous dealer charges for what should be a simple maintenance operation.



These threads typically begin with a discussion of the process of actually physically replacing the battery. This aspect will, in part, attract a number of comments depending on how easy or difficult it is to reach, remove and then replace the battery, this of course depending on its placement. There will be a discussion of the sources for a replacement unit. Candidates may vary by market but I think it’s fair to say that the consensus is that the brand of the factory fitted battery is not important and that any battery from a reputable manufacturer the same spec (conventional lead – acid, AGM) group number, capacity and CCA) can be successfully used.



And then the fun begins: REGISTERING THE BATTERY! Topics under this heading typically include the need for registering the battery, warnings about what will happen if the battery is not registered, how to register the battery, devices that can be used to register the battery and foibles and failures of the process. The following discussion will address the 1st 2 of these – need for registering and consequences of not registering. While I cannot be certain that I have read all of these threads in detail (some are more than 1000 entries long) I have not yet found a satisfactorily clear and cogent explanation of these aspects.



To begin I would like to add a well accepted “law” to the above noted general acceptance of alternate sources.



Ohm’s Law E= IR



Where E equals voltage in volts, I equals current in amperes and R represents resistance in ohms. Like any equation with 3 variables choosing 2 determines the 3rd . In practice, resistance is typically a property of the system and choosing the voltage determines the current or, conversely the voltage can be very to achieve the desired current flow. Is there anything beyond these 3 parameters that the battery management system can see or control?



With the above as a basis I shall construct several scenarios and pose questions about them in hopes of determining if this apparent registration requirement really exists and, if so, why. The logic appears to be that the complexity of modern charging systems and the existence of different types of batteries with different optimal charge profiles means that the car must “know” what battery is installed in order to charge it correctly.



Scenario 1: old battery removed, functionally identical new battery installed. The car already “knows” the type and specification of the battery. I find it very difficult to believe that the color of the battery, the name on the battery or a number on the battery representing its position on the production line are relevant. The only possible differences a difference in the state of charge of the old and new batteries. (A state of charge difference could have occurred without changing the battery had, for example, the headlights been left on with the engine off.) This assumes that the car had not “lost its mind” when the old battery was disconnected and all retained information was gone. This would suggest that every time the battery is disconnected for any reason – service and repair safety etc. – the registration process would have to be repeated. Is this the case?



As a subset of the above, can one attach a backup battery or charger to retain the memorized settings during the changeover?



Scenario 2: in a car with limited use and without a maintenance charger, the battery health has degraded due to sulfation. Does the charging system recognize this and, if the battery has been removed, desulphated and then charged to standard specs, will it be necessary to reregister it?



Scenario 3: in a case where a battery has gone completely flat, for example, running at night with a faulty alternator, will reviving the battery with a good 3 stage charger trigger the need for registration?



What are the consequences, if any, of not registering the battery? At this point, all I have seen are cryptic comments to the effect that “you will run the new battery” or veiled threats such as “try it, you’ll see” What actually will happen and why?



At this point my reaction is that “battery registration” is part urban legend, part the medieval churches response to any scientific question “Aristotle said…..” and a more modern take – “proof by blatant assertion”



Shields up Scotty!

 

I believe the battery registration is a result of many vehicles having adopted, in theory anyway, a "smart charging" type capability..

Think of a modern "smart charger" like a NOCO. You do need to at.least tell it what type of battery you are charging. Presumably, it uses different algorithms based on type, condition, etc. That said, the smart charger does not ask for the date I or other info, it seems able to calculate overall condition.

The bigger problem is that the manufacturers use obtuse coding, or proprietary scan images not available or easily interpreted by the owner. Why not just clearly print the "BEM Code" on the battery so that it can be entered right from the dash. Why not just prompt for Ah, yymmdd, type and Ah? The coding is intentionally made complicated so dealers can charge $1000 for a $200 part and 15 minutes of labor.