Jaguar I-Pace 12V Battery Replacement
Pre-MY21 cars carry two 12 V batteries, a large flooded starter battery and a small AGM auxiliary; later cars have one. Both age like any car battery, and the small one often goes first. Charge and load-test before buying, then fit by size, with the car asleep and the cable ends insulated — done that way the electronics need no relearning.
How bad is it · Garage, carefully
Replace a failing 12 V soon — it can stop the car without warning
When the 12 V gives up the car cuts its link to the pack and can lose braking assistance and the park lock. An old battery that throws warnings won't get better on its own.
Which one applies to yours depends on your symptoms, your model year and what has already been done to it.
Likely causes, most common first
Read the check cost before the odds: a free check that rules a cause out beats a likely guess that costs money.
The small auxiliary battery has failed (pre-MY21)
The auxiliary is a 15 Ah AGM that supplies the brake booster, the parking lock and the front inverter. On pre-MY21 cars it is the battery that fails most often.
Brake and gearbox messages, the car refusing to come out of Park or shutting down and needing a tow, while the doors and screens still work.
Measure the auxiliary on its own, rested. It sits on the opposite side from the starter battery, buried near the heavy red and black cables.
A JLR auxiliary or the exact equivalent Exide EK151 (15 Ah, 150 × 90 × 145 mm). About 20 minutes out and 15 in, no coding needed. Mind the small positive cable's 8 mm nut: overtightened, it can twist and crack the fuse terminal.
The main starter battery is worn out
The big 47 Ah flooded battery runs almost everything and wakes the car. With no alternator it lives on DC-DC top-ups, and at around three to four years it starts to fail, sometimes with no warning at all.
Over a month the charging voltage on a monitor drops, for example from about 14.4 V to 13.6 V, and the resting voltage from just over 13.0 V to 12.4 V. A high-voltage system error can clear once a bad 12 V is replaced.
Charge it and have it load-tested. Search by size, not by car: group T4 or 99R in the US, 063 in the UK; JLR lists Interstate MTP-T4 for the US and Canada. Take the old battery and hold-down to the shop to check fit.
A replacement starter battery fitted at home without removing the storage box. MY21-on: Service Mode first where the app offers it, terminal nuts to 12 Nm, then recalibrate the one-touch windows.
Both batteries after a deep discharge
Once both have been run flat, for example after the pack emptied on the road or weeks of standing, replacing only the main battery often changes nothing: the auxiliary is gone too.
A new main battery and still a dead car, or the same warnings within days.
Test both. If one has been deeply discharged, plan on both.
Both replaced together, for example Varta EK151 and EA472 for about £88 delivered, with both new batteries fully charged before fitting: no software relearn was needed afterwards. Dealer quotes for the pair run to several hundred pounds or dollars.
Warnings or dead switches after the swap
Disconnecting with the car still awake, a cable touching the body, or a new auxiliary that arrived half-flat can leave modules confused or a fuse blown.
Steering-wheel buttons unlit and dead, or Reduced Brake Pedal Feel, straight after new batteries.
Charge state of the new auxiliary, every connection refitted, no blown fuse. Ask which modules were reprogrammed and which codes were stored.
Worth trying: disconnect both again, wait about 16 minutes for full power-down, reconnect cleanly. Steering-wheel buttons can also come back after a few drives. The battery monitoring sensor on the starter battery's negative post can be reset with a diagnostic tool or left to self-adapt.
The order to check them in
The point of the order is money: each step either rules a cause out or makes the next one worth doing. Green is free, amber costs a little, red is the one to arrive at last.
Charge and test before you buy
A battery that charges and passes a load test means the fault is elsewhere — look at the charging side instead.
cheapKnow which car you have
Pre-MY21: a starter battery under the black cowl at the base of the windscreen on the passenger side, and a small auxiliary on the left. MY21 on: one battery.
freeBuy by size
Starter: group T4/99R, UK 063 (Exide EA472 fits). Auxiliary: EK151, 15 Ah. JLR hasn't approved lithium replacements.
cheapAlarm while charging a flat battery
Press unlock on the fob to silence it; holding the fob under the steering column and pressing start also disarms it.
freePrepare the car
Charge the new batteries fully. Service Mode in the app where offered, then lock and wait until the hazard switch dims, 15 to 30 minutes.
freeDisconnect in order
Earth first, and insulate every cable end you take off: the charging system can energise the positive side. Keep cables off the body; a touch can blow a fuse.
freeRefit and finish
Positive then earth, nuts to 12 Nm. Leave Service Mode, recalibrate the one-touch windows, and check for messages on the first drive.
freeWhat it usually isn't
Don't spend money here first:
If none of this finds it:
On jagaux.com
- Jaguar I-Pace 12V Battery Drain, Car Won't WakeIf new 12 V batteries keep going flat, the car isn't going to sleep.
- Jaguar I-Pace Key Fob Not WorkingA dead car that ignores the fob may just need a fob battery.
- Jaguar VIN decoderConfirm your exact model year, engine and factory options before ordering parts — free.
Ratings, fuse numbers and torque figures vary by model year and market. Read the legend on your own car before pulling anything, and use the figures in the manual for your car, not the ones in a video.
Check your VIN: exactly which car you have and which bulletins apply to it.