Do I need to register the battery in my car?

The Battery management system in newer cars is a little misunderstood………

Most of the time you can get away with just swapping the battery and

have no issues at all, but what happens when a simple battery install

turns into a nightmare because the old Alternator isn’t working

properly with the new battery you had installed? So lets take a quick

look at the tech and see whats happening.


The battery management system watches the state of charge of the

battery and tells the alternator when to charge or not charge, to keep

up with the power demands of the vehicle, and to make sure the

Alternator isn’t just jamming along at 100% charge rate and making your

fuel economy go to crap and all sorts of electrical tomfoolery.

On some newer vehicles the current State of charge (SOC) requires

registration via a scan tool and some models have various tricks or

can automatically deduce this information if the vehicle sits for X

hours etc etc.

So all battery registration does is tell the Battery management

system about whats going on with the charging system. And this extra

piece of programming tells the car to be prepared for this different

and or new battery, that may have a smaller or larger power capacity.

If the car battery is dead or close to being dead and you replace the

battery, the BMS might think there is still a shit battery and may

have the old “state of charge” stored in the BMS. This old Information

being incorrect causes the Battery Management System to keep pushing

more unneeded power into the battery thinking its still helping out

the crippled old battery that’s no longer there!

In turn this excess power can create a little havoc by overcharging

or not charging a battery at all….who knows what a none calibrated

component will do? Or maybe the car came with a standard wet cell

battery and you swap an AGM battery into the Car, Mr. Sensitive

battery Management system thinks its charging a regular battery, The

AGM may have different charge cycle requirements and with its brain

out of wack could damage the alternator or battery.

My question is, would you hook a charger made for flooded batteries up to a AGM battery to charge it? I think there is more to the battery registration than we think.

So lets talk about some basic BmS……

A charging scheme, does NOT maximize the battery ON time per charge.

The charging scheme has the ability to reduce the battery’s lifetime if

it needs more charge and discharge cycles. A weaker battery discharges

faster. This also occurs on the discharge cycle, the weaker battery

trips the discharge limit faster on most BMS systems than a good


So weak battery more charge time, Good battery less charge time.

So if you replace a 700 Amp hour battery with a 400 amp hour battery

what happens? the charge/discharge cycle changes and the Alternator

turns ON and OFF more to keep up with the reduced power capability

of the smaller battery. And vice versa, If we change from a AGM battery

with a longer charge/discharge capability to a lead acid battery with

30 or 40 percent less power storing capacity and the Battery

Management system still thinks it is trying to keep a Larger Capacity AGM battery in top

shape! So whats wrong?



  The BMS is programmed for a BIGGER battery!

The BMS goes through its normal discharge/charge ON/OFF cycle and now your new

battery is  dead, your trying to price a new Alternator when that’s not the issue!

Now lets look at going from a weaker flooded battery to a bigger

battery, The charge discharge cycle is set at a faster rate, So the

BMS is still trying to keep a smaller battery charged, this faster

charge/discharge ON/OFF cycle keeps the battery charged but reduces

the life of the battery, batteries can only charge and discharge so

many times before they are crap! so there is no issue until you need

a new battery every year and you are wondering why new batteries are

so shitty.

The main issue I have seen with the BMS systems on newer vehicles, is not very many mechanics and car owners know that there is a battery control system at all! So when the car starts to act up and there actually IS an issue with the battery to save money and time they run to the nearest parts store and get a battery installed. Parts stores have been installing batteries for years for free (unless its buried in a wheel well or in an odd place) And after installing a battery in a BMW or a Newer Ford (most other makes also) the customer goes along their happy way and the next day the battery is dead or weak, they run back to the parts store and the battery is checked and charged and put back into the car. This process continues without any mention of Resetting the BMS in the Computer at all! A few makes and models are known for needing a proper reset of the battery system (Ford and BMW are big culprits) to make everything sync up and work right again. So next time your vehicle starts acting stupid and you change the Alternator and or Battery 4 times and the battery is still dead, Might be a different issue all together.

Does your BMW need a New Battery Every year?

The Car more than likely requires the Battery Management system to be programmed to see a new or different type of battery! Skipping the Battery registration your car might think its trying to keep an 8 year old 600 CCA Flooded battery charged, when you just had a shiny new AGM battery put in…….

On most of the Newer BMS systems the BMS itself can deduce the state of charge/depth of charge and program itself according to the current it measures and a few other variables, Sometimes “programming the battery” is as easy as leaving your vehicle off and locked for 8 hours.


Battery Management Systems have been around for many years and are not “new tech”. Uninterruptible Power Supplies, Android phones and Laptops have Battery Management Systems so Don’t take a Simple thing and turn it into a witch hunt……

Below is a picture of the voltage reading of a battery not charging because of an issue, Many times more modern charging regulators and BMS systems will be at the bottom of the charging cycle and the voltage output reading below 13 volts will trick mechanics into thinking there is some kind of issue when there is not.




In the picture below, After repairing the issue in the charging system, charge voltage is back to a normal level, but this higher charge voltage can be missing at the bottom of a charge cycle, once again a perfectly working Alternator and/or charging system tricking you into thinking there is an issue. On many newer vehicles the Alternator output will be negligible if the Battery is at 100% charge, and a reading as low as 12 volts may be seen. Once the charge cycle starts you will see the Alternator start to activate and voltage will be somewhere around 13-14 volts on most Average cars.



So……. What car brands have the Battery Initialization or coding function?

General Motors






Land Rover


















Now Lets look at a List of supported Vehicles on a popular Battery Reset tool!



A list of BMW’s that have BMS systems that

require Registration of the Battery.

2002 and newer 7-series E65/66 chassis

2003 and newer 6-series E63/54 chassis

2004 and newer 5-series E60/61 chassis

2006 and newer 3-series E90 E91 E92 AND E93 CHASSIS

2007 and newer X5 series E70 chassis

2008 and newer X6 series E71 chassis

The Foxwell NT510 can perform a battery registration on BMW’s and have a pretty good list of supported Brands.

The Carly app can also do more advanced coding on the BMW

Here is another list of supported Models For Battery learn function of another scan tool!

Aveo 2012-2017

Cobalt 2012-2015

Cruze 2012-2017

Sonic 2012-2017

Spark 2013-2018

Tracker 2014-2017

Malibu 2012- 2017

Captiva 2011-2017

Impala 2014-2017

Orlando 2014-2017

Trax 2014-2017

Buick lacrosse 2017

Buick Envision 2017

Cadillac ATS 2013-2017

Cadillac CTS 2014-2017

Ford BMS? F150 trucks out of a Manual

Charging System

The charging system is a negative ground system consisting of:
• a generator with an internal voltage regulator
• a charging system warning indicator
• a battery
• circuitry and cables
• a PCM
• a radial arm adapter (serviced separately from the generator)
• a battery current sensor (this is what’s in the picture)
• a generator current sensor

The generator is driven by the accessory drive belt. When the engine

is started, the generator begins to generate AC voltage which is

internally converted to DC voltage. The DC voltage is controlled by

the voltage regulator (located on the rear of the generator) and

supplied to the battery. The PCM controls the voltage regulation set

point, working with the generator internal voltage regulator over 2

control and communication circuits.

This vehicle is equipped with load shed strategy. The Body Control

Module (BCM) monitors the battery state of charge using the battery

current sensor
attached to the negative battery cable and the battery open circuit

voltage as measured by the BCM during 8 continuous hours of vehicle

sleep time (ignition off with doors closed).

With the engine off and the ignition in the ACC, RUN or delayed

accessory position, when the BCM determines the battery state of

charge is low, a message is sent to shut down the audio/navigation

system in order to save the remaining battery charge. Under this


• the Front Display Interface Module (FDIM) displays SYS OFF TO SAVE

BATT (without navigation) or BATTERY SAVER — SYSTEM OFF
PLEASE START THE ENGINE (with navigation).
• the Instrument Panel Cluster (IPC) message center may also display

TURN POWER OFF TO SAVE BATT (base message center) or TURN POWER
OFF TO SAVE BATTERY (optional message center) to notify the driver

that battery protection actions are active.
• the battery indicator may also illuminate.
If the vehicle battery has been charged or battery replaced, it takes

approximately 8 hours for the BCM to learn the new battery state of

charge. During this 8 hour period, the vehicle must be undisturbed,

with no doors opened or keyless entry buttons pressed. If the vehicle

is used before the BCM is allowed to learn the new battery state of

charge, engine off load shedding may occur earlier than normal and a

message may be displayed.
If the vehicle has been jump started, engine off load shedding can

still occur and a message may be displayed until the BCM determines

the battery state
of charge is above 40%.

With the engine running, when the BCM and Power Steering Control

Module (PSCM) voltage is low, a message is sent from the BCM to either

minimize or
shut down the climate controlled seats, rear defrost, heated mirrors

and Dual Automatic Temperature Control (DATC) blower motor to improve

voltage. Under this condition, the IPC message center displays either

FEATURES TEMPORARILY TURNED OFF (optional message center) to notify

the driver that battery protection actions are active.

So another question? (……… If Initializing and/or coding the battery isn’t a required process when changing a battery, why did many of the car manufacturers add in a option/method in the ECM or BCM  to do it?

What about Hybrid Batteries? Yep, Same story, Same type of Battery Control! Just a little more high Tech.

  Hybrid/EV Battery Pack Capacity learn function List



Cadillac EV models


As I find them I will add them.

Thanks for reading, Check in occasionally for periodic updates to this Page. J~