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 an AGM battery
charged what happens?
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
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 4 times and the battery is still dead, Might be a different issue all together.
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……
So……. What car brands have the Battery Initialization or coding function?
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!
Malibu 2012- 2017
Buick lacrosse 2017
Buick Envision 2017
Cadillac ATS 2013-2017
Cadillac CTS 2014-2017
Ford BMS? F150 trucks out of a Manual
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
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
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
LOW BATTERY LESS FEATURES (base message center) or LOW BATTERY
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~