I have the same model and I had the exact same symptoms last year. It’s the auxiliary battery (the small one) that needs to be replaced. It is not monitored and it gives no warning; it’s not expensive and you can do it yourself. It’s under the right panel in the trunk (boot). You don't need any tool for reset after replacement.
Check this thread for more info: https://www.fullfatrr.com/forum/topic65051.html

Where are the two batteries and what are the specs please? 2018 P400e AB LWB

The main one is under the compressor under the spare wheel, the second is behind the cover on the right side of the boot...

IIRC The specification depends on the model and extras it has. Ten minute job to uncover them to check what spec yours are...  Pete
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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

No spare wheel for the PHEV, nor can you open up the area under the boot floor 2018 P400e AB LWB

Oh dear, sorry, can't help then.... does it not say in the Hand Book..?? Pete
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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Handbook is in Dutch unfortunately and I never figured out where or how to get an English PDF version. JLR seem to have this annoying app to help you figure out features, but no simple PDF version of the manual 2018 P400e AB LWB

Assuming it has an auxiliary battery and it’s the one causing the issue, as Pete says above, its generally located behind the right hand side boot panel which should pull off with sharp tug - my 5.0 SC needed a new one when the stop/start stopped working, easy job to replace. Jonathan

2007 Defender 90 XS Hardtop

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No spare wheel for the PHEV, nor can you open up the area under the boot floor

Of course you can open it! Pull the handle to raise the floor cover, then remove the foam insert with the tire repair kit and admire the 12v battery, the subwoofer and the 14.7kWH Samsung Li-ion battery...

Click image to enlarge

wow! Thanks!

So we have two batteries like very other RR 2018 P400e AB LWB

The main battery is 12v 90Ah AGM (absorbed glass mat) and the secondary one is 12v 14Ah (mfd by Exide). For the secondary one, as JCW wrote above, pull the side panel to acces it.

Quote:

Handbook is in Dutch unfortunately and I never figured out where or how to get an English PDF version. JLR seem to have this annoying app to help you figure out features, but no simple PDF version of the manual

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So we have two batteries like very other RR

Actually, we have three

@AnnualMan:

EDIT: If we’re talking about the main battery:

Yes, you’ll need access to an iiD tool or something like the iCarSoft LRV3 can be had for £150, and a tool worth having IMHO. “If it ain’t broke, don’t fix it” -where’s the fun in that?

Last edited by Gremlin500 on 3rd May 2023 4:30pm. Edited 1 time in total

Big thanks for all the useful information and suggestions! I’ve ordered the battery tester and also booked the car in at a specialist to give it the once over.

Fingers crossed all is well! 2018 P400e AB LWB

I had the ‘won’t start’ problem yesterday, though a bit different to any I’ve found in the search

Pressed the button after the FBH had been on 10 mins, dash lit up, then after a few seconds just a ‘click’. No cranking, no ‘low battery’ warning (which I have occasionally had).

Yesterday at 10:30 it was -6 so who knows what it was in the night. But 48 hours before I’d just done a 190 mile journey in a oner so surprised it wouldn’t crank.

Anyway, 10 mins on the ctek (which went straight to stage 3 which means more than 12.6v) and it started. Took 2 goes as the bloody push button start cut the motor before the engine had fully fired but then we were away.

Probably the original battery too - so will have a new one come service time - hopefully this is all it is as the car will probably end up in ‘real’ cold in the alps next year! 2019 MY SDV8 Autobiography in Velocity Blue
2018 SL63
2022 iX3