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Discussion Starter · #1 ·
In vehicles made before the 2021 model year, there are two 12V batteries. These are located in the frunk under the center removable panel and easily located by the red caps on their positive posts.

The larger battery is referred to as the starter battery. This one is oriented differently from model year 2021 onward.
The smaller battery is referred to as the auxiliary battery. This one is not present from model year 2021 onward.

They supply 12V power, or act as a buffer, for the low voltage (non-driving power) circuits in the car. These include the instrumentation, infotainment, sensors, door locks, power brake booster, climate, power steering, mirrors, electric parking brakes, etc.

During normal operation of the car fully powered up the 12V is supplied by the DC-DC converter that draws power from the 400V traction battery and steps it down to 12V to supplies the needs of the low voltage devices, but they still need the batteries as a buffer, or to operate when the car is powered down.

The auxiliary battery powers the (1) power brake booster, (2) the front EPIC (electronics for the front motor), and (3) the parking pawl in the front motor/axle/transmission. When this battery fails, it can cause messages to appear on the instrument display that are related to reduced power, reduced braking power, and gearbox faults, as well as not releasing the car from park. The messages are due to the fact that the EPIC is not getting its 12V to operate properly, and the brake booster is not getting its 12V to operate properly, and there isn't 12V power to operate the parking pawl to release it.

The starter battery is supplying 12V for all the other low voltage devices. When it fails you may not be able to unlock the doors, you won't be able to release the bonnet (hood), you may have a very quick shutdown of the car, the displays won't light up, more nasty messages appear on the instrument display (before it quits), the alarm system won't work, etc. It is not a driver friendly experience.

DO NOT IGNORE MESSAGES AND CONTINUE TO DRIVE. You will risk a complete shutdown in traffic and that could be rather hazardous.

Known causes of battery failures are: normal aging, missing software updates, power supply distribution box failure. DC-DC converter failure, BSM/GWM failure, wiring harness failure, loose cable connections, BCM failure, BECM failure.

Get the vehicle to a dealer as soon as possible. It may require being towed on a flatbed tow truck. If out-of-warranty, the starter battery can be replaced by a 99R/T4 size battery. Unfortunately, the auxiliary battery is an odd size and can only be sourced (as far as we can find) from a JLR dealer in the US and Canada, or ordered from European sources that can supply an Exide EK151 battery. Replacing a battery won't do any good if the fault is one of the other causes. Charge and test a battery before replacing it. A good battery would indicate the fault is something else.

If one is lucky enough to be where a 12V battery charger, or booster battery, is available, you may be able to power up the car using these on the affected battery/batteries. This should be done with the expectation of getting the vehicle on a tow truck or to a dealer (if very nearby). Once powered up, the DC-DC converter may be able to supply sufficient power to keep the vehicle going. However, dead batteries sometimes act as a big power sink and prevent cars from being powered up or continuing to run. Be sure that the boosting source is connected to the positive post of the battery and grounded to the body of the car (not directly to the negative post of the battery).

If you need to get into a locked car, try using the fob or Jaguar app (or equivalent) to unlock it. If that fails, the fob contains a mechanical key. It can be inserted to a mechanical lock located behind the driver's door handle. Push the front of the handle (near the small button) inwards to pivot out the back edge and pull out the handle as far a it will come. This will expose the door lock and you can operate it with the key from the fob. Turn the key clockwise in the lock to unlock the door. Once in the car, you can open other doors by pulling and releasing the interior door handles twice.
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If you need to get into the frunk, there is a manual release cable behind a black plug in the right side footwell. Unscrew it (yes it is a tedious operation) and pull the release cable.



Once you have the frunk open you can remove the center panel and get to the batteries and manual release for the parking pawl.

Release the parking pawl by lifting the lever up 90 degrees. This will allow the front wheels to roll. The electric parking brakes in the rear will still keep the car from rolling if they are applied. You should chock the wheels just in case they are not before releasing the parking pawl.


To release the electric parking brakes, you need to power up the car (one press of the start button with foot off of the brake). You will need 12V from the starter battery circuit to do this. Supply a 12V booster source if needed. Then follow this procedure:
  • Block the car from rolling by using something as a wheel chock on a front wheel and a back wheel
  • Press the start button once without foot on brake and if the car doesn't power up you can stop here
  • Press the brake pedal all the way down and hold it there
  • Lift up and hold the parking brake switch (down by the driver's knee) for at least 1 second and you should hear the parking brakes release as well as the brake symbol on the left of the instrument display go off
  • Press the start/stop button once or twice (as needed) to power off the car and you should not hear the parking brake activate
  • Release the brake pedal and parking brake switch
** Caution at this point since the car may roll without warning if the parking pawl has been released and wheel chocks are not used. **

If this procedure does not succeed, then "skates" should be used under the rear wheels to pull the car onto a flatbed tow truck.

If pulling the car onto a flatbed tow truck, retrieve the tow "hook" from under the loadspace floor and screw it into a position on the front or rear of the vehicle as appropriate (behind one of those small caps in the bumper covers). It is left-hand thread so turn it counterclockwise to screw it into the car. If you are not able to power release the rear hatch, lower the rear seat back sections to get to the loadspace area and lift up the floor.

Additional notes:

I recommend using a charger or other source to supply at least 15A as a alternate 12V source for "jumping" either or both batteries. Lower amperage chargers can be used if you want to try recharging the batteries but they will take a lot longer. They do not have the power required to operate the parking brakes.

There are Bluetooth battery monitoring devices available that connect across the battery terminals and allow monitoring of battery voltage via a smartphone. You might consider adding these and checking that voltages are dropping below 10V at any time. A low voltage of less than 10V indicates a dying battery or a charging system issue. Search your favorite shopping website for "12V battery monitor Bluetooth".
 

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Discussion Starter · #5 ·
The best way that I know of is to regularly drive the vehicle. The car will charge the batteries as you drive and a regularly driving it will make sure they get topped up without relying on the car's monitoring while the car is shut off. Of course, this requires that all module programming is up to date.
 

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Your basic garage can replace the main 12v battery without much fuss. I think one should assume that 24-to-30 months is the total lifespan of the regular (passenger side) 12v battery. The smaller 12v (more rectangular in shape on the driver's side) may require dealer assistance. My 12v died in small-town VA and I had it replaced by a nice guy that had never worked on an EV, let alone a Jag EV, so there you go (nearest Jag dealer was a LONG way away). I'll probably head over the dealership and insist the other one is replaced in another month or two.
 

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Discussion Starter · #7 ·
@dernotte found a useful video that demonstrates various items mentioned above such as the manual door lock, manual bonnet release, and parking brake release.

 

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Impeccable timing. Last Monday (a week ago), I just had the starter battery die and was totally caught off guard. Fortunately it was in front of my house. Wish this thread existed a week ago but I ultimately YouTube trained myself and connected a charger to the starter battery. Was then able to lock/unlock, etc... I charged the starter battery overnight with a 6A charger. In the morning it was acting normal. Took it to the dealer and today they finally got to running the diagnostics on it (3 other I-Paces ahead of me for the same issue). This is a 02/19 car so pretty sure the batteries are just old but since it's still under warranty, they wanted to run all the tests. So now I wait a few more days for replacement aux and starter batteries to arrive. Then they run the same tests again to verify before releasing it back to me.
 

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2019 First Edition , just under 3 years, 27,600 miles. After overnight charging, got in the car, "Traction battery fault", "OK to drive with caution Brake pedal feel reduced", car would not shift into gear, and shut down after about 10 seconds with the "P" indicator on the shifter and the main display blinking for about 30 seconds. Tried to start multiple times , same result.
Luckily, read this blog frequently and recognized its probably one of the 12v batteries. Put a trickle charger on the 12v aux battery ( drivers side US spec) overnight. Next morning, after several tries, car started and pretended like nothing happened.
Drove the 15 miles to the St Petersburg FL dealer, dropped it off. Told them the story. They dont have a qualified I Pace mechanic, will have to send it up to Clearwater dealer, 10 miles up the road ( We are fortunate to have 3 dealers in a 30 mile radius of Tampa, 4 if you count the new dealer in Lakeland , 5 if you include Sarasota). No loaners cuz theres nothing on the lot, and estimated 3 weeks to get it back.

Got it back today after just 9 days. Clearwater replaced the starter battery - 861501 startup battery renew 77711 WJS. Also replaced aux battery - 861503 auxiliary battery renew 77711 WJS. Also did updates to Electric Power Inverter Control (EPIC) B, C, AND D. Updated the Battery energy control Module (BECM). Updated Power Control Module (PCM). Updated the Gateway Module (GWM). For the battery Charger Control Module they replaced the ECU.

Seems good now. Still love the car. Probably have to pry it from my cold dead hands.

Mike S.
Tampa, FL
2019 I Pace First Edition, Photon Red
 

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Awesome write-up, thanks a lot.
One point from personal experience: when the car gives a warning about failing 12V battery, do not turn it off, as most likely it won't be able to turn on again until the battery is replaced. Proceed with caution to the location where you can comfortably wait for the tow truck.
What's happening, is this. When the battery degrades over time, it looses usable capacity, and at the same time increases internal leakage. The car's charger is continuously monitoring current, and when it's reaching certain level due to leakage, it generates that error. But while the charger is active, the battery can still sustain usable voltage. Things go south when you power off - then high internal leakage quickly drains already low capacity, and the car turns into a real estate.
In my case, wife pulled over and powered off hoping that it will clear the error, and the car got stuck. The only way I could recover it - bring the truck and kick the battery with jumper cables (which is a risky arrangement I admit). As the current in this case is limited by internal resistance of the batteries only, it quickly gains enough capacity to start the car and drive to safe place, but usually damages the battery even more. Predictably, attempt of charging it back home overnight at 6A setting gained nothing, so still flatbed to the SC.
 

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Discussion Starter · #12 ·
As mentioned in the first post, the starter battery is a 99R/T4 size. You can find these at Advance Auto Parts, Oreilly's Auto Parts, etc. The auxiliary battery is an Exide EK151. Not sold anywhere in the US/Canada that anyone can locate. The posts on top of it are small and I haven't found any suitable ones to screw onto a typical utility/motorcycle battery. I even stopped in a Jeg's store and we exhaustively went through what was available in their supplier catalogs. You can get an EK151 shipped here from Europe. Search Ebay (for example) to find the vendors.

Of course, you can get "genuine" batteries at a JLR dealer though they may have to order it and get it from JLR. Supply may vary at any time.
 

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If 12V issues start to happen to you and you're afraid to turn the car off for fear of it not coming back on, remember this trick:
Put car in Neutral, apply Parking Brake. Now you can unbuckle and get out of the car without it shutting down.
 

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As mentioned in the first post, the starter battery is a 99R/T4 size. You can find these at Advance Auto Parts, Oreilly's Auto Parts, etc. The auxiliary battery is an Exide EK151. Not sold anywhere in the US/Canada that anyone can locate. The posts on top of it are small and I haven't found any suitable ones to screw onto a typical utility/motorcycle battery. I even stopped in a Jeg's store and we exhaustively went through what was available in their supplier catalogs. You can get an EK151 shipped here from Europe. Search Ebay (for example) to find the vendors.

Of course, you can get "genuine" batteries at a JLR dealer though they may have to order it and get it from JLR. Supply may vary at any time.
For those that are interested, we had both of the 12V batteries in our 2019 SE replaced by the JLR dealer last week. Scheduled it 6 weeks in advance so they would have the batteries. Total cost was $868.74 with labor and SC tax.
 

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Discussion Starter · #15 ·
Is your car beyond 60K miles? Why wasn't it covered by the 5 year/60K miles warranty? Was this at your request as preventative?
 

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If 12V issues start to happen to you and you're afraid to turn the car off for fear of it not coming back on, remember this trick:
Put car in Neutral, apply Parking Brake. Now you can unbuckle and get out of the car without it shutting down.
There is also a timer that kicks in (about every 14 minutes I believe) that tells you to push the brake pedal or the car will shutdown. We have had to push it 4 times one night when the Mexican restaurant gave our order to someone else and we had to wait for them to redo our order!
 

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This all happened to me 70 miles out from dealer -- at the furtherest point. I just told the whole strory under the "Would you recommend the I-Pace?" I have a 2020 almost 3 years old and driven very lightly -- 17K miles. The brake went hard as I was driving which made it harrowing -- Has to be the 12v battery -- sadly this car has been in the shop so many times!!! AC issues and then while in shop care caught and ripped front bumper on lift! Also had trouble with tow truck driver getting it into neutral -- would have helped to see all of this for sure. Sadly I cant remember passcodes. The violent rattling vibration is absolutely horrifying -- like the car is going to blow up! Happened today 11/6/2022. Sometimes I feel these cars should be replaced -- continual flaws
 

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Good lord. As a prospective owner all these stories of the 12v battery are really steering me away from the car.

2019 First Edition , just under 3 years, 27,600 miles. After overnight charging, got in the car, "Traction battery fault", "OK to drive with caution Brake pedal feel reduced", car would not shift into gear, and shut down after about 10 seconds with the "P" indicator on the shifter and the main display blinking for about 30 seconds. Tried to start multiple times , same result.
Luckily, read this blog frequently and recognized its probably one of the 12v batteries. Put a trickle charger on the 12v aux battery ( drivers side US spec) overnight. Next morning, after several tries, car started and pretended like nothing happened.
Drove the 15 miles to the St Petersburg FL dealer, dropped it off. Told them the story. They dont have a qualified I Pace mechanic, will have to send it up to Clearwater dealer, 10 miles up the road ( We are fortunate to have 3 dealers in a 30 mile radius of Tampa, 4 if you count the new dealer in Lakeland , 5 if you include Sarasota). No loaners cuz theres nothing on the lot, and estimated 3 weeks to get it back.

Got it back today after just 9 days. Clearwater replaced the starter battery - 861501 startup battery renew 77711 WJS. Also replaced aux battery - 861503 auxiliary battery renew 77711 WJS. Also did updates to Electric Power Inverter Control (EPIC) B, C, AND D. Updated the Battery energy control Module (BECM). Updated Power Control Module (PCM). Updated the Gateway Module (GWM). For the battery Charger Control Module they replaced the ECU.

Seems good now. Still love the car. Probably have to pry it from my cold dead hands.

Mike S.
Tampa, FL
2019 I Pace First Edition, Photon Red
@msoby Were all the modules replaced under warranty? And did they update all the firmware/software as well?

The question I have: Does updating the hardware (EPIC, BECM, PCM, GWM, wiring harnesses, etc -- that is a LOT) and all the software essentially fix this issue?
 

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Good lord. As a prospective owner all these stories of the 12v battery are really steering me away from the car.
Unfortunately this is not an issue unique to the I-pace. Many other EVs have very similar 12v battery issues with similarly dire symptoms when the 12v battery dies.

In the case of the I-pace the only "hardware" issue that really matters from what I can tell is the wiring harness. The software updates alone went a long way towards preserving 12v battery life.
 

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There is also a timer that kicks in (about every 14 minutes I believe) that tells you to push the brake pedal or the car will shutdown. We have had to push it 4 times one night when the Mexican restaurant gave our order to someone else and we had to wait for them to redo our order!
@Trielectric
If you buckle the driver's seat belt and leave the key fob inside the car you will get 2-3 hours of ON time before the car warns of a shutdown. Useful for the future!
 
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