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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?
Better late than ever NO my 2016 does not have a start stop battery. And as of today, I am still working well with the BMS out of the system and always enjoy coming to the car with a completely full battery.
Last edited by chasers03; Jul 25, 2025 at 11:16 AM.
Large charging system fault, symbol, and words disappear when hitting menu, but others remain.
[img alt="Antigravity battery tracker ranges from 95 to 99%
"]https://cimg9.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/920x2000/img_0561_9a64f0127ed854ee895ef6d21c93687979165f92. png[/img] Antigravity battery tracker ranges from 95 to 99%
[img alt="To get rid of the annoying large warning light I push menu OK button
"]https://cimg4.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/920x2000/img_1663_835f366488bfb6000e68d310a22319e787fffd6c. png[/img] To get rid of the annoying large warning light I push menu OK button
Last edited by chasers03; Jul 25, 2025 at 01:36 PM.
Reason: Clutter
This is from the workshop manual on the BMS calibration:
BMS Control Module Self Calibration
The BMS control module periodically initiates 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 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.
Given this, what are the low-voltage thresholds for the lithium lightweight batteries? If the vehicle charging system doesn't allow the battery to drop below 12.2 V, are either of the PowerTex or Antigravity batteries setup to go into their safety mode at or above 12.2 V?
I guess I am just confused why these batteries are right at the knife's edge when being used.
Last edited by 71camaro; Jul 26, 2025 at 03:38 PM.
He was the first to completely disconnect the BMS with his Lithium battery and, like Captain Kirk...
I am now convinced "this is the way" - just clear the "Charging System Fault" message by pushing the OK button and start driving, Lithium or AGM battery...You end up with a fully charged battery after every drive and the voltage will not drop precipitously every time you open the door.
Last edited by JagCode3; Jul 27, 2025 at 12:39 AM.
Just installed a LiFePO4 H8(49) 90AH 1300CCA battery. Kept the BMS connected just to see what happens and did not reset the BMS. Staying rock solid between 13.3 and 13.6V with no big drops below 12V like before.
40 pound weight difference was nice on the back muscles! No need for venting either.
If this works out I am never going back to AGM. I will start capturing some data.
Just installed a LiFePO4 H8(49) 90AH 1300CCA battery. Kept the BMS connected just to see what happens and did not reset the BMS. Staying rock solid between 13.3 and 13.6V with no big drops below 12V like before.
40 pound weight difference was nice on the back muscles! No need for venting either.
If this works out I am never going back to AGM. I will start capturing some data.
What brand?
I'm curious how it goes, I really want to do a lightweight battery to offset sound deadener I've installed.
for my doors for sound deadening and waterproofing (created a semi-circle hood to divert rain and wash water from the rear of the lowest speaker).
I also did the rear area behind the subwoofers and eliminated rattles one by one by playing some very deep bass hip hop songs. You can cut strips of the sheet and slap them down like paper mache anywhere you want to tamp down a rattle. It's like whack-a-mole. The butyl backing makes it easy to remove also.
Very inexpensive compared to other brands. I have a convertible so did not tackle the trunk. I think it could be quite beneficial for the coupe.
This but obviously modified for our cars. Not cheap, but top quality. I figure what I'm using in the trunk weighs about what a lightweight battery will take out. That, wheels, carbon ceramic brakes (if I can find the necessary bracket for the rear) will lighten the car up a noticeable amount, I expect..
Just a quick update. With BMS connected and disconnected there wasn't much difference in charging parameters for both the AGM and LiFePO4 battery. I was very disappointed that disconnecting the BMS did not result in a sustained > 14V charging situation while driving.
Interestingly I did not get an error code after disconnecting the BMS. However the problem is this: The JLR alternator usually stays around 13V during driving and only spikes briefly past 14V for charging purposes during deceleration or when you open the driver's door. For the AGM battery this is barely adequate. For the LiFePO4 battery it is a gradual killer, as the voltage will actually trend down during a long drive to an unacceptable low SOC. You could potentially be stranded as has happened before:
So I returned the LiFePO4 battery. The JLR BMS still cannot fully charge any (Lead-acid, AGM or LiFePO4) battery during a long drive. If you need a quick battery charge and don't have a charger, just idle for a few minutes with the driver's door open. You will get a sustained 14V charge that will drop as soon as you close the door.
I hope that the advice to "take a long drive to charge your battery" disappears from this forum. The JLR BMS is not designed this way. Your best bet is periodic trickle charging when not driving the car. For those who have successfully run LiFePO4 batteries in their F-Types I would love to know what your average SOC is. 12.5V in an AGM battery is 90% SOC vs 20% SOC in LiFePO4:
Last edited by JagCode3; Sep 15, 2025 at 10:21 AM.
I always continuously monitor the charging voltage in my car via the Torque app and a plug in voltage monitor at the cigarette lighter outlet. They are always both in agreement. The charging voltage in my car is always between 14 and 14.5V so my experience is not the same as yours for some unknown reason. Although I did reset the BMS with a Jaguar iCarsoft tool when I recently changed the battery.
Thanks for that, wish that were my case. I wonder if different model years have different parameters. There are so many varying experiences on the forum.
Thanks for that, wish that were my case. I wonder if different model years have different parameters. There are so many varying experiences on the forum.
I can't remember what year and model you have and am disinclined to go back through the thread to find out. You might consider adding a signature with that information. Mine is a mid-2016, but very early 6MT.
Regardless, I never had issues when I was driving more or less daily, and it's only since I started working remotely that I need to occasionally put the car on the C-Tek. More often recently since I put a "Mouse Blocker" under the hood, so by ten days or so without driving, I get the low battery warning.
Large charging system fault, symbol, and words disappear when hitting menu, but others remain.
[img alt="Antigravity battery tracker ranges from 95 to 99%
"]https://cimg9.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/920x2000/img_0561_9a64f0127ed854ee895ef6d21c93687979165f92. png[/img] Antigravity battery tracker ranges from 95 to 99%
[img alt="To get rid of the annoying large warning light I push menu OK button
"]https://cimg4.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/920x2000/img_1663_835f366488bfb6000e68d310a22319e787fffd6c. png[/img] To get rid of the annoying large warning light I push menu OK button
The above is a repost of my experience with my very expensive Antigravity Battery coupled with their Battery Tracker app and my 2016 F type R BMS unplugged. I am very happy with the outcome [except for those 2 little red warning lights]. The Battery reports staying always in the 13.64 voltage / 95% range regardless of sitting or running. I never have to connect a trickle charger, nor come to the car and have to use the battery remote to reengage the battery because the Antigravity BMS prevented it from going below the 12.2 volts which that silly Jaguar BMS repeatedly cycled the charging system to let the alternator not function [theoretically to get maximum life from the standard glass pack / AGM battery] BTW the Antigravity tech support people told me this always charging 13.5 volts or more was desirable for the Antigravity H7/group-94R which I have...
Hoping that someday someone of our very smart owners will figure out how to hack the software of the F-type. It has lots of opportunity for improvement....
@chasers03 thanks again for your pioneering work. Unlike your experience I disconnected the BMS and only got the fault once and never again. The alternator charged only at 13V with brief spikes above 14V during deceleration only. This behavior did not change with BMS connected or disconnected. I gave up on experimenting and realized the LiFePO4 would leave me stranded eventually as I only do long drives.
