Garycw

The remote batteries are not re chargeable It takes a button battery 2032 in each.
Disconnect battery cables then charge battery before reconnecting cables, touch the beg & POS together. Then reconnect. The 2033 batteries don't last a very long time, but should start car holding in correct spot on dash.
The battery charger can mess with electronics, so disconnect

Greg Elmassian

The battery charger indicating "things are fine" is actually only indicating that the battery voltage came "up" to the expected level after "charging".

Under load, the voltage of a defective battery can drop too much. You could put a voltmeter on the battery AFTER you remove the charger and see what is up.

Interesting, to remove the battery cables and touch them together. I get the idea, but I know on my 2002 A8L, if the power ever went out for a long time, my radio locked up and needed the secret code to re-enable it.

Taking all the car electronics to complete zero concerns me, although maybe that is ok now.

Greg

abarmard

I hate to disconnect the battery, then I have to reprogram all the things like radio, driver seat, etc. again. By the way, in 2012 A8L is the battery located in the left back wing in the trunk?
thx

the_duke

No. The battery is under the spare tire. I am not sure what happens with a D4 when you unhook that battery as I haven't tried it yet. The D3 only lost the clock. All other settings remained.

But before you go there did you ever measure the voltage?

Garycw

I had my D4 battery disconnected for about 20-30 min and didn't loose anything

RED HORSE

If the battery has been on a Cetek maintainer, then the first thing I would do is disconnect the charger and check the battery voltage. Personally I've had good results in my Porsche keeping it on the Cetek for lengthy periods of time. I would expect it to be 12.5 v. If it is, then I would change the battery in the remote. These are two simple things that are easy to try before beginning a more lengthy trouble shooting.

Garycw

The 7 stage smart chargers are the way to go. I still wouldn't want more than a trickle with cables hooked up

Jack88

As has been said, check the batteries in the fobs, if they are original they are coming up on due for replacement. That you couldn't even unlock it with the fob makes me suspect the batteries in them have died as opposed to anything wrong with the car. If the battery is at the right voltage, even if weak, it still should be able to unlock it if nothing else. If your interior lights all come on as normal, your battery is plenty up to the task of at least receiving commands from the key. I know Autozone usually has a little thing on there counter that will tell you if your key fob is completely dead. It's a device that looks for the RF signal produced when you hit the buttons on your fob.

Greg Elmassian

Just put new batteries in the fob, most people do not have lithium battery checkers, and again, batteries need to be tested under load.

Greg

Garycw

Just replace them. They're cheap. I bought 10 for $5 enough got 2 D4's and 2 for Lexus LS460. And still have spares to keep in cars. Don't waste your time checking them