First, thanks for a great post. One of the better ones on LR4 charging systems.
Which brings up the issue of RV/camper (house) batteries. I would think most keep their camper batteries charged to optimal levels while at home and then connect the "house" battery to the engine battery (charging system) thru the "tow package" connector for the camping trip/drive to campsite. Given the charging profile of the LR4 this appears to be a bad choice unless the RV/house battery is isolated at the higher state of charge. The LR4 charging system would actually bring the house battery down to the 12.25-12.30v resting state.
Better to isolate the LR4 completely from other battery systems. Looks like I have some IID tool work in my future.
You're correct. The smart Traxide isolator does indeed keep them connected, resulting in a low state of charge (12.3-12.4) in both. When I installed the Traxide I expected to see a low starting battery, but a high 2nd battery being held in reserve. But, the Traxide just dumped any extra voltage from the 2nd back to the starting battery, so they'd both draw down.
But not sure that the solution is to isolate them... the problem is that the charging system never really pushes out enough power to get either battery back up to a full state. They get a nominal 12.7 float that you see right after driving, but quickly drop to a core resting state of about 12.4, which is where they generally live.
I think its a design point issue that Rover thought through (sacrifice battery life for fuel mileage). And, it's generally not an issue for 99% of on-road, mall-going users. It's only when you need the extra amperage when remote camping or running accessories like winches, refrigerators, etc. So we'll just continue to see owners chase the LR4 weak charging profile in posts about eating batteries in 2-3 years instead of the normal 4-5. And, as a note, there is no magic battery brand or type that will fix it. Dealers will also tell you the system is working great even when you get the "low battery" dash warning when parked listening to the radio with a 2 year old battery. There's just not enough juice being fed to the battery.
For the off-road remote campers, or owners who want 4-5 years from their batteries, older owners have learned to add back the missing power. They either connect chargers once a month or, like me, keep a small solar panel setup on the roof to bring the batteries up to above where the LR4 likes to keep them.