The BMS adapts the charging characteristics and passes information about the state of charge to other ECUs. If you do not reset the BMS everything will still work, but if your battery was older or degraded prior to replacement, everything will work at a less than optimal level. Range Rover L322s and L405s used to throw faults every now and then due to discrepancies in the voltage the BMS was expecting and actual battery voltage - but it's been so long I've forgotten what the details were. Aside from everything else, your new battery will likely not last as long. It is worth having the reset done if you do not have a GAP IIDTool yourself.

 

If the battery has been degrading over time, the charging system adapts and pushes more amps to the battery to keep it alive. When you replace the battery the charging system needs to know so it can go back to charging normally.
This might not be the case with this battery. This one sounds like it just discharged through no use. Slap in a new one and you should be good. If it was mine I'd take it out and put it on the "big charger" overnight and see if I could get it to take a charge. If it does, it's probably ok. If it didnt, then I would replace it.

The seat doesn't need to be unbolted, just push it all the way up first, then forward. That's enough room to get it out.

 

Ok, the journey continues! I had to rejump the "darn" thing so that I could adjust the seat. I figured that would be way better than taking the seat out. I moved the seat UP and FORWARD as much as I could continually. Still not enough, but it worked.

Here's my steps, saved for posterity. Or the next time I need to pull this thing. I always say - don't Google your symptoms. It will always come up something freaky! I'm going to add to that adage: don't look at the Shop manual. Holy cow that thing will scare the bejeezus out of you. Here's my steps:

1. Use the trusty 10mm Knipex spanner to pull the black/negative/ground terminal.
2. Per Simon/Powerful UK, unclip the BMS wire from the black/negative/ground. This makes it way easier to get that terminal out of the way.
3. Use a 13mm socket and remove the "near" end of the red/positive/charge. This makes it way easer to slide the battery out without having to "pecker" with reaching into the pit of despair. Reminded me of the old "Flash Gordon" film where they random reached into the tree to see what bit them. I could just imagine cross arcing something reaching up there.
4. Use a 10mm socket with an extension to pull the two bolts that hold the battery bracket in. In my pic, it's on the far left. You can see the pile of sweat from a humid Virginia afternoon.
5. Try to find a sucker, minion, young adult, someone who owes you a favor. Worse case, wrestle that thing forward. I'm at the end of my fifth decade in life. Still feeling fit, but no longer as lean as I once was. I was able to tilt it forward, slide my sacrificial fingers under the edge and then lift with the left hand while pulling the handle with the right. That was able to slide it forward for the next step.
6. Pull out the breather tube from the "front" of the battery (towards the engine).
7. Lots of other side cables on the red/positive/charge, so now I took my trusty knipex 10mm and removed the terminal.
8. Say some prayers like Fred Sanford and heave that puppy out.




I'm sure the install will be the reverse. I'll post some tips if any come up. The exciting thing now was to find a replacement AGM battery that could pull 850 CCA as a Group 49 / H8. I looked EVERYWHERE. Napa, O'Reilly, Advanced Auto, AutoZone. They all had plenty of Duracell, DieHard, and other more questionable batteries. I was looking for an Interstate or Exide to no good luck. So, to my surprise, Amazon would ship me one! Sadly, it won't be here until Friday. I'll post my exploits as they continue. I'm already wiring in my CTEK Convenience Charge connector so I can, to quote @Dogpilot "keep it on life support" the next time I abandon it for an extended time.

While I wait a week for a battery: any thoughts on long term storage? If I'm going to leave this thing parked again for a couple months, thoughts on what to do? I'm thinking of putting the convenience charge directly to the battery and pulling the black/ground/negative terminal from the Defender to just kill it of all power leeches, vampires and other hair brained tech that some genius in JLR thought was important to keep active.

 

So sad to hear your battery has died. Wow, I did not think it was that bad to take it out. There must be a trick to it, seeing the dealers must be doing this almost daily. I thankfully have never done a removal. I got the "I have a bad feeling about this super picky warranty coverage." So they have to do it for me until the end of time.

Reality, if you're going to store it again I would put it on maintenance trickle charge. I do it with the airplanes as their batteries are beyond expensive aside from being installed in even stupider and hard to get at locations (they tend to be installed in a location beneficial to the center of gravity). I am very religious about keeping it on a trickle maintenance charger in the winter. Naturally it is an again, stupidly expensive unit for 24V. The CTEK is supposed to be able to do maintenance. Now maintenance and keep up with the vampire drain the system has may be out of its capability. The safest way would be hook up directly to the battery, with one of the leads disconnected. One side effect, it will cause the system to do kind of a reset when you hook back up. I really don't know what parameters are kept in non-volatile ram and what will vanish after a prolonged disconnect. The dealers place the car on an un-interuptable power supply to keep it from loosing data. So the emissions parameters are re-set, but the car regenerates those in about 30 minutes of running. Things like all the web and CarPlay setting may not be retained. You will have a preview of that when you get the new battery sorted out. It will be interesting to hear what was not retained.

Yes I do miss the hand crank as well. Aside from the novel way to start the car, it was helpful to adjusting the valves as well. If you do remove the battery for storage, do not put it on the garage floor. It really does discharge the battery very, very slowly (something to do with acids, condensation and grounding). Put it on something insulating, like a piece of wood. On a plus note, my small extra battery installation seems to keep mine from dying. In fact I have not have the farting noise warning of low battery for over a month now! Seems that now, when I open the door, instead of draining the battery for 10 minutes, it is kind of putting a small charge on the main battery. I kind of expanded the system by adding another one of the same battery in a tiny pelican case. I use it for powering the survey ground station, but now it doubles the backup power to 40ah.

There seems to be an epidemic of new cars dying in airport parking lots. Anytime anybody walks up and clicks their key, it wakes up all the cars in range, doesn't unlock them, just puts them on alert. This happens 100's of times a day. Cybertrucks have it even worse, they try to cool the battery pack during the day, effectively killing them off in two weeks. Modern cars seem to be way behind in considering the real world demands on their pathetically designed electrical systems. I pine for the hand crank and a fusebox on the firewall that held 4 glass tube fuses, two of which where spares.

 

We have had this discussion before, but I paid for school by managing an auto electrics shop and got to see and work on exactly these 2/3 glass fuse electrical systems. I promise that aside from creating the evil empire that was Lucas, these electrical systems are the very worst thing the Brits ever did to the world of automobiles.

2 examples:
- a late 70's Land Rover, lets take a 2 door Range Rover with 3 glass fuses of around 35A each (I can't remember the exact values - been too long). To put that into perspective (for everyone, not you DP), 35A was enough current to power every electrical accessory on the vehicle simultaneously and around the peak of what the alternator produced. LR engineers ran an 18ga wire (0.8mm2) from one of those 35A fuses to the brake light switch at the top of the brake pedal, then up the A-pilar and under the headliner to the back of the vehicle, down the C-pillar to one taillight, and finally down under the tailgate and across to the next taillight. When a RR of that era was rear-ended and one of the taillights shorted, it became a race between the 35A fuse or that 12'-15' long, very skinny wire to see which would melt first. While I am not aware of any vehicles catching on fire due to this, the long wire under the headliner would get hot enough to destroy the wiring harness and melt itself through the headliner. So a $500 repair (at the time) for a rear body corner and taillight for a RR became a several thousand $$$ repair to replace the headliner and wiring harness and R&R the dashboard and most of the interior of the vehicle to replace the harness.
- in order to avoid the fiasco above and protect smaller components, LR (and other Brit auto makers) used in-line fuses buried somewhere in the wiring harnesses. This may have been ok for a 1948 Series 1 Land Rover where the electrical system consisted of 7 components and everything including the wiring harness was in the open anyway. But by the early 80s this had become a huge headache for even seasoned technicians as blown fuses were generally not an everyday occurrence and nobody knew where the in-line fuses, by now hidden below carpets, covers and layers of sound deadening, were. And don't even get me started on something like a Rolls Royce of that era. Everything electric but everything analog. And fused by the most well hidden in-line fuses imaginable to man. Give me digital any day of the week, month and year. And give me a decent fuse box with appropriately sized fuses and individual circuits. And in that era, give me a German car to work on.

As we've discussed in other threads, power draw at rest is a big issue for modern vehicles. And I also do not understand how (especially) LR could release (especially) the Defender without addressing this issue. But we are looking into it in the aftermarket. We'll see what we can come up with.

Tesla (or any EV) is a different issue, btw, and it's not just the CyberPOS. I know, I own 2 (not CyberPOS's). Lithium batteries regardless of their chemistry (LFP or LMN or whatever) like temps in the same range as humans. And especially LMN batteries do not like extreme heat, such as car interiors in airport parking lots in the summer. So the batteries have to be cooled. And that takes a lot of power. I can not think of a solution for this other than shade and a charging cable to every parking spot. Or a taxi to the airport.

 

This thread has become a very interesting read for me, having recently purchased a 2024 110 P525. I appreciate the conveniences and upgrades that the new car's systems provide (and I just started dabbling with the Gap iiDTool).

However, this thread has me concerned, especially as the problem appears somewhat endemic to modern cars.

Are there CCF settings that can be altered to reduce the battery usage while the car is parked (the comment above about the cars waking up when someone uses their FOB in an airport garage made me wonder)?