I didn't want to hijack anyone's post sorry if this has been beat to death but i am perplexed.
2018 F-type sat dormant from June till mid Sept of this year no charger/ tender used car started right up in Sept when i got it. I have driven the heck out of it since with no issues, last week i put a battery tender pigtail on the battery in the trunk plugged it in to verify it was working and it was. Unplugged to drive car. Have not touched car for 10 days (and did not plug in tender) came out to cover and plug car in for Ohio winter and the car is dead really dead.
thanks to this forum i already have the battery out and on a charger (it system checks battery and says it's ok just dead) and is currently charging.
Finally the question- is this just coincidence or did hooking the pigtail up do something ?
anything i should do different when i put battery back in?
any thoughts or help are appreciated
Thank You
Bryan

 

Well, my first question is this: when the battery was still in the trunk did you hook the connectors directly to the battery? Or properly to the ground point on the trunk floor and the connector bar (which has a black cover,)?
If you connected to the battery directly that might have had an effect since the battery management system is thus taken out of the loop. And it might indeed just be a concidence. Modern batteries do not do well with being deeply discharged and leaving the battery for several months means that it is discharging continuously during that period. Yes, the engine started but leaving the starting system intact as long as possible is designed into the system.

 

I connected the positive to the open spot on the T connection and the negative under the bolt for the negative connection.
I took that connection point from another forum member here.

 

Here is pic from member thunder dump

 

I've had no issues with this connection direct to the battery and the CTEK properly goes through its stages.

 

Is it safe to assume you leave it unplugged for extended times? My thought is this was a coincidence. Battery still charging when done i will reinstall and if everything works correctly plug in tender and check her throughout the winter.

 

Did you plug anything into the OBD port? (I have to ask)

 

No i have not and it hasn't been in for service since June. Good thought i have seen many people have that problem seems weird to me that that would cause an issue all though it obviously does.

 

It's a weekend car, so it may be plugged in for four days, then not for three, etc. Since I added the hardwire setup I probably have had it unplugged a couple times for 10 days or so.

 

Quick update battery is fully charged and reinstalled, started car let it run for about 15 mins in garage and everything seems to have reset. Plugged into battery tender and is showing all ok. Just seemed really weird that 10 days after putting pigtail on it was dead. Thank you all for help and input. Hopefully good when better weather strikes.