Hello F-Type battery enthusiasts. As many of you are aware, the BMS behavior can be vexing and disappointing. A large percentage of electrical issues for these cars seem to be traced to low battery charge.

I installed an Ancel BM300Pro to start getting some objective data because of this issue. Here are my first set of observations:



1) Car driven one hour starting with a brand new Interstate AGM fully charged battery (on Deltran 1.25A battery tender for several days) then parked and locked. What should be a fully charged battery from the alternator is instead at 12.3V with 50% state of charge (SOC). Battery tender then initiated. Voltage increases surprisingly fast to 12.8V over 1 hour.

2) Over 24 hours the battery tender charges to (yikes!) 14.6V (100% SOC) then and immediate discharge occurs to 13.1V (still 100% SOC).

3) Battery tender disconnected, car still locked. Slow drop from 13.1 to 12.9 over 2 days.

4) Car unlocked. Voltage immediately drops from 12.9V to 12.5V (80% SOC) over 1 minute.

For Contrarians and BMS Defenders, yes, this may be unique to my car alone, but I doubt it. For those who believe you can top up the battery by just driving it for a while, it is a myth IMHO. My next experiment will be using the CTEK 7002 charger instead of the Deltran to see about the 14.9V to 13.1V rapid discharge. I don't see how these rapid discharges can be good for the battery but I may be wrong. From the Tech bulletin:


I would be interested in others' experiences.

 

Do you have the document which that snippet came from? I’m interested in the context. I’m curious if it means that BMS will allow the battery to discharge to 75% before initiating charging?

Your step 3 could be related to surface charge dissipating…
https://mechanics.stackexchange.com/...attery-testing

Where are you measuring the voltage? Waking the car up might cause a voltage drop on some of the harnesses.

I’m neither a contrarian nor BMS apologist, but I am a retired EE (and I stayed in a Holiday Inn Express.) Your step 4, where apparently 20% of capacity is lost in 1 minute, would require something like a 1200 amp discharge rate for 1 minute. (20% * 100Ah capacity * 60 min/hour = 1200 amp-minutes). Which would blow fuses and melt wires. I don’t doubt you measured this, but I can’t explain it.

 

@DJS very glad to have your EE expertise! The Ancel is hooked up between the positive and negative terminals of the battery. The battery tender is hooked to the positive terminal and chassis ground in the trunk (not the negative terminal).

Can't find the pdf but here's the full document (Thanks to Christian over on the LR Forum):

BATTERY MONITORING SYSTEM
Battery Monitoring System Control Module
Single Battery and Dual Battery System Vehicles
NOTE: The secondary battery on stop/start system vehicles is not fitted with a BMS control module.
On all vehicles a BMS control module is located on the primary battery negative (-) terminal. The module is located on the battery post and is clamped to the post with a bolt and nut.
The primary battery negative ground cable is connected to the BMS control module and is attached to a ground stud on the vehicle body.
The BMS control module is connected into the vehicle wiring harness via a multiplug. The BMS control module receives a 12V power supply direct from the primary battery positive terminal. A LIN bus connection provides communication between the BMS control module, the GWM and the QCCM (Quiescent Current Control Module) for control and monitoring of the battery current drain and state of charge. The BMS control module measures battery current and voltage, which it communicates to the GWM over a LIN bus connection.
The GWM transmits the battery information over the CAN bus to other vehicle systems. Based on the information received from the BMS control module, the GWM and the ECM will control the output from the generator and request the switching off of electrical loads if necessary.
CAUTION: Due to the self-calibration routine, it is recommended that all power supply diagnostic testing is carried out using the Land Rover approved diagnostic system rather than a digital multimeter.
The BMS control module is able to generate DTC's to help diagnose primary and auxiliary battery or generator power supply issues. These DTC's can be read using the Land Rover approved diagnostic system. The Land Rover approved diagnostic system can also be used to implement a primary and auxiliary battery and generator self test routine.
For additional information, refer to: Battery (414-01 Battery, Mounting and Cables, Diagnosis and Testing).
If a fault is detected, the GWM and the ECM will override the BMS control module.
The BMS control module DTC's can be used to help diagnose battery or generator power supply faults. The DTC's are stored in GWM. The Land Rover approved diagnostic system has a process for an automated power supply diagnostic procedure. The procedure provides a menu driven process to locate a fault in a logical sequence. The procedure uses the capability of the BMS control module and generator LIN bus controlled functions to provide current flow information and will detect if the BMS control module or generator are functioning correctly.
BMS Low Battery Warning and Energy Management Messages
The BMS continuously monitors the condition of the primary vehicle battery. If excessive battery discharge occurs, the system will begin to shut down non-essential electrical systems in order to protect the battery.
If the BMS calculates that battery condition is not within set parameters, there are 3 messages that can be displayed, 2 on the touch screen and 1 on the message center. These inform the user that the battery is either at a low level of charge or the engine-off power consumption limit has been exceeded.
Low Battery - Please switch engine on or system will shutdown in 3 minutes: is displayed as a Warning on the touch screen if the engine is not running. This indicates that the battery has fallen below a predefined threshold. As soon as the battery is charged back above this threshold then the message will be removed.
Low Battery - Please start your engine is displayed on the message center if the engine is not running. This indicates that the battery has fallen below a predefined threshold. As soon as the battery is charged back above this threshold then the message will be removed or it can be manually removed by pressing 'OK'.
System will shut down in 3 minutes: is displayed as an Energy management on the touch screen if the engine is not running, and system features are causing excessive battery discharge. After 3 minutes the BMS will begin shutting down vehicle systems. Normal system operation will resume when the engine is started. This is based on a percentage of battery capacity available for the customer to use with the engine off. The percentage can change based upon several factors.
Once triggered, the resetting of this message will not occur until the vehicle is driven for 10 minutes with the engine running (to allow the battery to recoup any lost charge). However, if the engine is run for less than 10 minutes, the message will only be displayed after an additional 5 minutes with the ignition on but engine off.

QUIESCENT CURRENT CONTROL MODULE - ALL VEHICLES
The QCCM is located right rear corner of the luggage compartment. An addition to the Battery Monitoring System, and using signals already transmitted by the BMS control module(s), the QCCM cuts power supply to other non-essential control modules to avoid excessive discharge of the primary battery. The systems supplied via the QCCM are the audio/entertainment systems and the climate control systems.
Some control modules can cause unnecessary battery drain due to the module staying awake after the vehicle electrical system has been shut down. The QCCM in conjunction with the GWM, monitor and control the systems to prevent battery drain.
The system consists of three components:
The BMS control module
The GWM
The QCCM.
The battery monitoring system checks primary battery health by analyzing battery quiescent current, battery current drain or state of charge, and determines if any action is required to protect the primary battery. If action is required this is communicated to the GWM.
The GWM control logic uses this information to determine if action is required to assist primary battery protection. The QCCM receives open and close commands from the GWM and reacts accordingly.
The software that controls the QCCM is contained within the GWM.
The system will be set in transit mode on delivery. Transit mode has no QCCM operation and the relays remain closed. Therefore battery drain could occur and the system will not react to it.
A PDI process requires the system to be put into Normal mode, which enables the quiescent current control module, before handing over to the customer.

The QCCM has a routine to clean the relay contacts if required. This routine is performed using the Land Rover approved diagnostic system and, if unsuccessful, the unit will require replacement.
The module contains a number of fuses which supply and protect the audio/entertainment systems, the climate
systems, the GWM.

GATEWAY MODULE (GWM)
The GWM is attached to a bracket, which is bolted to the passenger side of the cross-car beam, behind the
instrument panel. The GWM contains software to control the following functions:
Determine condition of primary, auxiliary and secondary batteries
Control the output from the generator using load management software
Controls stop/start system using power management to inhibit unnecessary electrical loads
Control the Power Supply Distribution Box to enable the switching of the battery inputs.
The GWM communicates with other system modules on the high speed CAN Powertrain and Chassis, and medium speed CAN Body and Comfort buses.
The GWM communicates with the BMS control module and the power supply distribution box via a LIN bus.

POWER SUPPLY DISTRIBUTION BOX
The Power Supply Distribution Box is located in the right side of the luggage compartment, rearward of the BJB. The power supply distribution box incorporates two banks of MOSFETs, which are activated by the GWM to switch the vehicle loads between the batteries during stop/start on vehicles with stop/start system, and also for charging the secondary or auxiliary battery.
The power supply distribution box receives a battery supply direct from the primary battery to BAT1 terminal and a battery supply from the secondary or auxiliary battery to BAT2 terminal. The power supply distribution box also incorporates a microcontroller, which receives commands from the GWM via a LIN bus connection. The power supply distribution box connects or disconnects either the primary or secondary battery to the vehicle loads according to the GWM commands. In addition, there is a diagnostic connection between the GWM and power supply distribution box, to detect faults with the power supply distribution box.
The MOSFETs in the power supply distribution box have a fail-safe Body Diode mode which will ensure there is always a connection from the primary battery to the vehicle loads in the event of a failure in the power supply distribution box. At least 60A can be supplied to the loads in this mode. The GWM will detect such a failure and will shut down non-essential loads so as not to overload the power supply distribution box.

OPERATION
BATTERY MONITORING SYSTEM AND QUIESCENT CURRENT CONTROL - SINGLE AND DUAL BATTERY SYSTEM VEHICLES
When the ignition is off (power mode 0), the BMS control module records the primary battery state of charge and begins to monitor the battery condition from this point.
If the battery state of charge falls by 7%, the BMS control module will monitor the primary battery for 5 minutes. The BMS control module sends a ‘warning’ message on the LIN bus to the GWM. If after the 5 minute monitoring period, the battery charge has continued to fall or below 50% due to the quiescent drain current being too high, the BMS control module will determine that some control modules are still 'awake'. The BMS control module sends a shutdown message on the LIN bus to the GWM. The GWM sends a CAN bus message on the medium speed CAN Body and Comfort, and high speed CAN Powertrain and Chassis networks to all control modules, requesting them to shutdown.
The BMS control module will monitor the primary battery state of charge for a further 15 minutes and determine if the battery state of charge is still dropping. The BMS control module sends a 'Power Disconnect' signal to the GWM on the LIN bus. The GWM then sends a signal to the QCCM on the LIN bus to open its internal relays. When the QCCM relays are open, the power supply from the primary battery to non-critical control modules is removed. The non-critical control modules are any modules associated with the infotainment system and also the climate control system.
The use of a LIN bus communication ensures that no other control modules are 'woken' during this process. If CAN bus communication was used, all modules on the CAN bus would be woken by the message.
BMS Control Module Self Calibration
Periodically the BMS control module will initiate a self-calibration routine. To self calibrate, the battery monitoring system first charges the battery to its full condition.
NOTE: If the vehicle is only driven for short periods the charging process could take a number of days to
complete.
Once the battery is fully charged, the BMS control module will discharge the battery to approximately 75% of its full state of charge, but never lower than 12.2 V. The time taken to complete this part of the routine is dependent on the electrical load on the vehicle.
When the second part of the routine has been successfully completed, the BMS control module will return the battery to its optimum level of charge. The optimum level of charge will be between 12.6 V and 15 V, depending on battery condition, temperature and loading.
The BMS control module also monitors the primary battery condition with the engine switched off. If a low voltage condition is detected the BMS control module can request the infotainment system is switched off to protect battery voltage.

DUAL BATTERY SYSTEM - STOP/START SYSTEM VEHICLES ONLY
The dual battery system prevents electrical loads on the vehicle being subjected to low voltage levels during an ECO (stop/start system) engine start. Low voltage can occur due to the power demand of the TSS (Tandem Solenoid Starter) motor and could result in degraded performance of components and/or system control modules. The GWM contains the software to control the dual battery system and electrical load management system to ensure that ECO engine starts do not affect other vehicle systems.
The dual battery system isolates all power supply sensitive electrical components which may be affected by low voltage from the primary battery due TSS motor operation, and supplies them with power from the secondary battery when an engine start is in progress.
The power supply distribution box contains two banks of MOSFETs, which operate to change the power supply into two separate circuits when an ECO engine start is required. Sensitive electrical components are supplied from the secondary battery. The primary battery power is used exclusively to supply the starter motor and maintain essential power loads to the engine management system required for engine starting. The power supply distribution box operates according to commands from the GWM over the LIN bus.

 

Thanks for that. I have a friend coming over shortly, but I’ll read through it later.

 

In my own experience, regular driving kept my battery in a good state of charge without the need for a maintainer. Until I started working remotely I didn't even have one, so almost six years without. I'd put that as evidence that the charging system is good enough on its own, and that it's a lack of driving that causes problems.

 

Continuing from the previous graph:


4) Unlocking (from earlier graph)
5) Ignition on, engine on followed by a spirited 90 minute drive
6) Ignition off, lock, CTEK charger initiated - went from 12.5V to 13V over 5 minutes.


So after the steep decrease after unlocking from the first graph above (4), a recovery occurred. I decided to take a spirited drive with lots of shifting, change in RPM and speed (5) to (6). No stereo or AC/heat. When I shut off the engine and locked the car (6) I ended up at 12.5V and 60% SOC which the CTEK picked up on.

Interesting findings during the drive - real-time voltage revealed spikes going past 14V during periods of RPM decreasing and lasting seconds. Curve was flat during RPM increasing or stable. No correlation with speed. Next drive I will take some screen shots with seconds as the x axis. The Ancel app records in 2 minute intervals.


@lizzardo I agree. As your F-Type is a paragon, can you measure your post-drive voltage and SOC after locking?

 

I can measure voltage with my venerable Fluke 77 Series II, but how would you suggest I measure SOC to give data that aligns with yours?

 

@lizzardo We could just use the table method as I have been using what the app is telling me. Interesting the differences in the LFP battery (ie Antigravity) SOC vs AGM and Flooded SOC if the BMS consistently keeps the range between 12.25V - 12.5V.

So I learned a bit about charging and both the Deltran and CTEK chargers use the Bulk > Acceptance > Float phases in their protocol. So that is not the BMS in action when the charge reaches ~14.5 and drops suddenly:


6) CTEK initiated
7) 14.4V sudden drop to 13.4V
8) CTEK removed


"This type of battery charging, consisting of multiple stages, is not possible with automotive-type alternator regulators"

Next set of measures will be the car resting (locked and unlocked) off the charger for several days.

 

Lots of interesting data. That section you quoted is part of the self-calibration routine, which the BMS runs ‘periodically’. When you installed the new battery, did you use an OBD reader to reset the BMS, so that it knows it’s new? It will continue to charge it like a worn battery until it decides to recalibrate.

When I replaced the battery in mine in 2020, I didn’t bother with the BMS reset, and never had an issue. Another forum member has mentioned that the life of the battery could have been shortened by improper charging until it recalibrated, but who knows.

Have you noticed if ECO mode works in your car? In my XE, ECO (start/stop) had not worked for a few years. When I replaced the battery this winter and reset the BMS (with an iCarSoft), it started working again.

 

Following.

I'm in the "Drive it periodically" camp. Our F still has the original two batteries, tho' the secondary battery seems weak (ECO start/stop works VERY seldomly).

 

@DJS Yes I registered the new battery after charging it fully outside the car then installing it myself via OBD2. Eco mode still works although I disabled it in the trunk.

My interest in this topic began when I first started reading posts in this forum, especially the low battery warning, SOS limited functionality, multiple error codes showing up at once, chassis ground deterioration, and the OBD drain issue. When I was working on replacing the Meridian system I got the low battery warning a few times specifically after unlocking and opening the door. The voltage would routinely go below 12V, which I knew was going to eventually take out the original battery which was 4 years old.

Keeping the battery on a tender while parked is good practice, but the BMS drops it down to 12.25V-12.5V as soon as you start up the engine. And that's where it stays. There is no topping up by the alternator on a long drive to 100% SOC based on my early data. That's why it would be interesting to see what others are recording.

 

My experience is that with the original battery, I very rarely got the low battery alarm even after the car sat for a couple of weeks at a time. When, after about 8 years of life, the battery showed signs of dieing, I replaced it with an Interstate H8 battery. I have to keep it on tender if I don't drive it for a few days. I did not reset the BMS when I replaced the battery.

 

I replaced my (at least 8year old) battery in my 2014 F-Type V6S. The battery was still okay but I did it just in case. After I replaced it I got really weird charging behaivior until I reset the BMS with an iCarsoft tool. Before resetting the BMS the charging voltage would almost never reach the 14.8 max (usually stayed at 12.5V) and after the car resting (2 to 3 days) after a long drive (2-3 hours) the battery voltage would never be higher than 12 to 12.3V. After the BMS reset the charging voltage when the car was running was always between 13.5 to 14.8V and the battery voltage after sitting for a few days was 12.6 to 12.8 volts. So it seems to me the charging system tries to keep the battery at around 12.6 to 12.8 volts.

Note: All my voltage measurements were with an Innova 3721 cigarette lighter plug voltage monitor that closely agreed with the Torque app ECU voltage data.

 

The chart might be useful for a disconnected battery but mine is in situ and I don't trust a straight voltage to SOC correlation. You can see why based on my measurements today.

I had the car on a C-Tek MXS-5.0 on Tuesday until it was showing fully charged and on maintenance. Additional information: I have a "Mouseblocker" device under the hood that adds to the resting draw. I checked voltages under the hood, so none of the readings are locked (can't lock with hood open).

• Unlock, open hood, read voltage: 12.19V
• Wait until system goes to sleep: 12.49V
• 30 minutes after going to sleep: 12.54V
• 90 minutes after going to sleep: 12.54V

I then ran a couple of errands. Two stops, roughly 15 minutes driving

• Voltage on return, engine on and idling: 14.84V
• Shut down, wait ten minutes, but not asleep: 12.40V
• 30 minutes later, sleeping: 12.56V

The SOC didn't go up after the system went to sleep: the voltage went up because the load was reduced.

 

@lizzardo Thank you for that - looks like we are getting the same results!

Here are some short-time interval driving screenshots:


A) Car not charged on tender. Unlock door - this time voltage drops below 12V briefly
B) Start ignition - note rapid rise to ~15V
C) Start driving - stabilizes around 12.5V


D) Driving with minimal shifting and RPM change


E) Driving with lots of shifting and RPM change. Spikes happen when RPM decreases regardless of speed. There seems to be a ~15V limit.

 

After several iterations of trying to wire around my 2016 R BMS with a Antigravity Battery I concluded that the BMS would continue to drain the battery on a regular basis resulting in having my Anti Gravity BMS disengaging and me using the remote to reengage. So now I have several months ago disconnected the Jag BMS and like that I am reading a constant charge of 93 to 99% & 13.76 V level on my AntiGravity battery tracker app. I just have to put up with the battery charging fault sign on the dash but now always have a full battery when I start up... Any ideas on how to eliminate the battery fault lights or fake out the BMS when it is connected??

 

Personally, I’d measure the charging voltage while driving to be sure the Antigravity battery isn’t being damaged. Their website says 14.6V max, though it does have some internal protection. (I’d measure either with a monitor like JagCode uses, or a cigarette lighter monitor.)

 

Good point @DJS although the periods of >14.6V are brief based on my measurements.

However, the JLR BMS likes to keep the voltage between 12.25V-12.5V which if you look at the chart in post #8 is <20% SOC for the Antigravity LiFePO battery - not good!

So @chasers03 I would have done what you did and disconnect the BMS. Not sure how to trick it to get rid of the message - this where we next an EE expert like @DJS! Perhaps hook it up to the secondary start/stop battery - does your 2016 have that?

 

So, this table is for deep-cycle batteries, which isn’t what’s normally used in cars. When I searched for AGM voltage tables to check the health of my XE battery, I found lots of voltage tables with slightly different SOC levels. I never did decide if there was a ‘right’ one.

My issue with disconnecting the BMS: as I understand the system, from reading the workshop manual, the BMS is used to monitor the state of charge and health of the battery. It sends data to the Gateway Module (GWM), which tells the voltage regulator inside the generator what voltage to produce. In the absence of BMS data, what voltage does it tell the generator to produce? I would hope some compromise between charging the battery and not damaging or overcharging it.

I don’t have a clue how to fake out the BMS. I assume it’s monitoring both charging and discharging currents and the associated voltages. If it’s really smart, it may integrate the currents to estimate how many amp-hours are in the battery, and by measuring the battery voltage, the age/health of the battery can be determined. That’s probably what the calibration routine is, that the BMS periodically runs.

 

I don’t have a second battery in the car and my conclusion is that whenever the BMS is connected to anything it tells my voltage regulator to cycle down into low 12 V range which my antigravity battery does not like, but apparently is required of the typical Jaguar battery which I disposed of a long time ago.
I run with the Battery Tracker showing a lot and here’s what it says 95% or higher all the time which my battery likes and the antigravity people say you can’t overcharge their battery at this voltage range.
I can hit menu and eliminate the one main battery fault symbol, but the other two stay lit aggravatingly.
I was hoping one of you electrical engineers would show us how to fake out the Jaguar BMS.
Car runs from 95 to 99% charge all the time without the BMS connected

Large charging system fault, symbol, and words disappear when hitting menu, but others remain.