Replaced teh batteries approx 9 months ago in both fobs since they would not even open the doors, After 9 months of good work, they are acting up. However, it is only after the vehicle has sat over night for more than 8 hours. The doors and tailgate open as usual. When I try to start with teh key in my pocket, it will not start and has error message to get the key or hold up to the steering column. This does not work. Sometimes if I use the fob to unlock/lock while in the vehicle this helps - sometimes not. How do I get my fob to work again?

 

Sounds like the battery is low again.
The batteries in my wife's fobs run out faster than mine. My guess is one of the buttons is being pressed while the key is in her pocket book draining the battery. But who knows? I keep extra batteries on hand now.

 

It only happened once to me so far after maybe 15 months but I had to replace the batteries in both remotes and everything went back to normal. I may have gotten more than 9 months as you did due to frankly not using the vehicle more than once per week although I note that my wife’s key fob (which is ever used) was totally dead whereas mine had some life in it giving symptoms similar to yours.

 

I've also found 'new' batteries to be hit or miss. Some of the cheaper ones are terrible, others that look like brand name can be poor too. Think some online retailers sell well past their shelf life too

 

I think these FOBs are spending their downtime doing malicious hacking invasion or something.

We have put new batteries in both twice in 33 mths. Audi Q5, not once, in 4 yrs.

 

Sounds like there is a warning on the instrument panel when the key fob battery is weak.
I found this note under the key fob battery but couldn't find a list of warning messages:
If the low battery warning does not extinguish, it indicates that the replacement battery is not in a new and unused condition.

 

This is really interesting as is I had to think about how we use our key fobs. The big zero. They stay in backpack / jacket / purse (not mine, but thanks) and we 100% do door handles or boot / trunk foot waving. We got into that habit coming off bike / hike / snowshoeing / ski / run etc where keys were buried. Heck I probably use the Remote App start / heat / cool down more than the fob. Is that weird?

 

The fob is always active due to being a keyless type so the battery is constantly being used. If you think about it, for keyless entry to work the fob he to constantly listening for a signal from the car (which the car will send when you pull the handle, press the exterior trunk release or wave your foot under the back) in order that it can reply.
When the key fob battery is dead or very weak it isn’t listening or is only able send a weak response if any, so the car doesn’t open. Your only option is to use the real key to get the door open. But how to then start the engine?
When you hold the dead fob in the right spot under the steering column it gets just enough wireless power to respond to the signal the car sends when you press the start button. (A bit like wireless phone charging or toothbrush charging except it’s really weak, just enough to power it, not that the battery inside can be charged anyway).
So even though we may not press the buttons on our fobs, they’re still running, even my wife’s spare key to my Disco that she has literally never used and was dead when I tried it.

 

@LoneStarLR thanks for the details, especially the dead fob safety spot. That must be similar to the band's battery-less access, and proximity for safety. I get the transponder thing, I was just curious if my fob usage (never see it as buried in jacket or pack) was common. I don't know about the fob but BLE has advertise and data modes. I wondered if fob has similar and and therefore different battery consumption profiles.

 

I don’t know what tech it uses and although not BLE, probably some sort of low power tech that can react virtually instantly to respond when needed if you grab a door handle.
I’m just making an educated guess as to how it works to be honest...
It does make me wonder if the JLR key fob battery consumption is unusually high vs other brands keyless fobs?