I have searched and haven't found anything venturing down this path.

We just recently picked up a 2022 Defender 110 X-Dynamic HSE. It has the 3.0, so the 48v "mild hybrid" system. I have been doing some digging and planning on adding a dual battery setup. With the concerns of the LR DC converter failures, I am looking at pulling power off the 48v side of the system before it gets to the LR DC Converter to charge the 2nd battery. Should alleviate extra power draw from the 12v system and hopefully extend the life of the LR DC Converter. A 48v battery has more "capacity and efficiency" over a 12v of the same size. This brings up a question:

Has anyone installed a second 48v battery and stepped down to 12v to supply power for overland accessories? Anyone have any experience or thoughts on going 48v vs 12v?

 

I understand the answers may still be useful and interesting but for what is your purpose? I ask because I've had a dual battery system in my lr3 for nearly its whole life since 2007/8 which has been wonderful for camping with a fridge and powering things not using the starter battery.

However, back then it was essentially the only option whereas now there are a plethora of portable battery supply options and ways to use and charge them - keeping it entirely separate from the touchy vehicle system as well as being multipurpose or for in different vehicles.
To me, the biggest benefit of a built-in system would be simply getting it tucked out of the way.

A downside to how I understand what you propose, is that it would not be usable at all for a self-recovery battery, like the set-up in my LR3 which can be "combined" for an emergency start. Basically self-jumping.

There are ways to rig a portable version to charge while driving as well as by solar. I do hate it taking up space but I also love that I can in an instant swap it for the bigger one or very easily replace it if it ever dies, or obviously use it instead in the Range Rover vs the Defender, or even to cover the garage freezer in a city power outage.
What would be cool is to install something that could supplement/backup the 48-12v / DCDC system so that the issues people are having, become unlikely.

 

I have looked into a portable power pack, and while not completely opposed to the idea, there are a couple of challenges that I have with them.

1) Storage space is at a premium and a good portable takes up a bit of it.
2) Our plans tend to change quickly which leads to overnight trips on the fly. I really don’t want to have to carry around a portable in the back all the time that screams “steal me”.
3) We are heading out on a 4 week trip up to Alaska here in a month. The logistics of charging from the vehicle still put strain on the 12v system.

I am trying to figure out how to not strain the 12v system by adding additional loads. The benefit of having a second 48v battery with a separate DC converter stepping down to 12v would also then provide another power source, 48v and 12v, that can be used in the event of a dead battery. A jumper to the 12v car battery with a momentary switch could easily provide a back up power source to jump the 12v car battery.

With all that said, there really isn’t much of a cost difference between a portable power solution and a built in. Just seeking some advice from the brain trust.

 

If your vehicle is still under factory warranty, be advised that any mods done to the electrical system could void your warranty. These cars are very sensitive when it comes to batteries. Just my 2 cents worth.

 

It has been out of warranty for a bit now, but my intention is to limit, not eliminate, the impact on the system. All while still being able to have a power solution that works for side adventures, which is why we purchased the Defender. Why have an off-road capable rig if you can’t go out and enjoy it?