I will be scheduling it, thank you

 

I can get this warning with 100% probability while camping. On the second day, no matter how careful I am about not opening the doors too much, it pops up. Start the engine, let it idle, it shuts itself off in 30 minutes, problem solved.

 

Today I drove into town (11 miles). There was no low battery warning when I left home. Warning appeared when I shut the vehicle down in town. Battery reading 12.4V. Anyone got any idea what is happening? It seems more likely to be a bad sensor than a bad battery...

 

your battery should be charged with 11 miles drive and 12.4v seems normal to me. if you have a warranty, its' good time to replace to new battery. =)

 

Out of warranty. I don't want to replace the battery (only 3 years old!) if the problem is in the sensor that tells me that I have a low battery, and not the battery itself.

 

Just have the battery tested first to determine if a replacement is needed or not. Then you can start testing related sensors.

 

It's much more likely that the battery needs replacement than a sensor. Besides, "the sensor" is likely buried in a very expensive module. Unfortunately, 3 years for a battery isn't unheard of, depending on weather and use.

Don't be fooled by a trickle charger making things seem fine. They are almost mandatory if you need to park it for a few weeks, but it's no substitute for a good battery. It could be that the next time you park it without the charger is the time it will refuse to start altogether.

Also, it's a real shame that JLR hasn't given the truck a "camping mode" setting that ignores the doors, etc.

 

You didn't mention where you are - this may be "business as usual".

I live in the hot Southwest, and by now the stats on four long term vehicles are that the batteries fail after approximately two years. This is the usual warranty term; sometimes, if I'm lucky, they fail just before the warranty runs out, sometimes right after. Jump starter being carried along into the cold (thankfully, they are smaller now) when the car is parked is the EDC item for all the family members now, regardless of the battery age.

Side story - I replaced the battery on a different brand vehicle myself; the dealer offered the "battery registration" service with the mandatory one hour service charge that exceeded the battery price, I said "**** it, I'd rather spend that on a new battery when the time comes", and neither the car nor the battery noticed it. That battery is now almost two years old, and is showing signs of aging, though CTEK still considers it good.

 

Horror story - the battery I just mentioned in the other post; I went to three different auto stores to test it, all three gave different results, neither conclusive The stumbling point was that one of them totally missed the battery chemistry, the other couldn't figure it out, and the third didn't even bother to check.

Anyone has a battery tester at home they like/trust, btw? Apparently, they're dime a dozen on Amazon now, but I have serious doubts about trustworthiness of something for $29.99.

 

I'm in the Pacific Northwest. Never very hot, never very cold. Usually batteries last about 10 years here.
An aside question: For the P400 with the "instant start", does this starter use the 12V system or the 48V system? Even when I get the warning, it starts right up - no sign of struggle whatsoever.