2012 Jaguar XK
I let my battery go complete flat.
I don’t drive it as much as I should and usually keep it on a CTEK trickle charger but didn’t do it this time.

The battery seems completely flat (it’s the original battery). The trunk and doors are locked.

I was able to connect the CTEK to the emergency supplemental battery terminal under the driver side rear fender.

It initially didn’t take any charge but I found a better ground and it started charging.

Once charging all of the lights (headlights, taillights) started flashing and I could hear relays clicking. Seems like it was trying to reset?

I was able to open the doors but not the trunk.
The flashing lights and relay clicking didn’t seem good so I unplugged the CTEK.

What should I try next?
I could try to let the CTEK to keep charging?
I could also call AAA and get a proper jump.

Thanks!

 

You need more juice than what that CTEK is giving you to get out of that hole.

 

What kj said, you need at least 10 amps.

Something like this will work.

 

Yep, dug in deep.

I gave it another try and the electronics freaked out, typical low battery. I did manage to open the boot.

I can either try a real charger or get a high amp jump from AAA. Other option if I can get the boot open again would be to swap out with a new battery.

 

You closed it? You probably don’t want to trust that battery, get a new one, and (I can hear some members screaming this) “charge that new battery fully before installing it”. Get yourself a ‘real’ battery charger, like mentioned above, it’s a great investment (bought mine, maybe 40 years ago, rarely used, but it’s there when I need it).

 

Your battery is so old that replacing it with a new battery is 100% required so shutting the boot again was a bit optimistic.

A CTEK is fine but it depends upon what model you have. Mine is a 10A CTEK smart charger which is permanently connected but also has a 10A supply setting so can be used as bulk, non-smart, charger in situations such as yours where the battery is so flat that a smart charger can struggle to start the recharge sequence.

Richard

 

So it's 11-12 years old? That might be a record!!! Most batteries last 3-5 years, I've been lucky a couple of times and managed as much as 6 years. Use and environment have a role in longevity as well.

 

At least 10 years old so yes probably a record. I kept it on the CTEK and So Cal is relatively easy on the battery. No hard starts.
I probably could have gone longer if I remembered to but the CTEK back on.

• Best plan at this juncture is to replace. I like Interstate and they are nearby but I will search the forum to see what is recommended.
  Should it be the AGM?- XK / XKR Battery Overview and Replacement Thread

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• Another lesson is that when the battery is this flat, disconnect the negative until fully charged again so the the electronics don't freak out.

 

I went with an AGM for my 2013 XKR.