For anyone who has been tracking my posts since I first purchased my XK a year ago, you would already know a couple of things. First, this car continues to be the most AMAZING and BEAUTIFUL machine I have ever owned. It just takes my breath away.

The other thing you would know is that I have battled a charging system issue from day one. This problem manifested itself as a series of electrical gremlins, known to be related to either a battery not fully charging, or a parasitical draw. Of course, multiple trips to the dealer always resulted in the dreaded "We can't duplicate your problem". I even started feeling like I was being a nuisence by coming back with the same issues time and time again...and so the problems continued.

until very recently...

A few weeks ago, my converible roof got stuck in the partly open position. I muscled it closed and took the car back to the dealer. They reset the roof, and at my request took one final look over the rest of the car's mechanical and electrical systems as the warranty runs out soon.

Two things resulted from that visit:

First, I have had no further issues with the roof.

Secondly, from that day onward, my charging system problems seems to have mysteriously vanished (after a solid year of aggravation). My battery stays fully charged even when the car sits for days. I have personally conducted several voltage and amp tests with perfect results. Also, where I used to have to leave the car on a battery tender for 12 hours after a week of driving to fully recharge the battery, it now requires less than two hours, which is consistent with my two other cars.

Hmmm, did the mechanics (during their inspection) find and correct a problem they could not find earlier and simply did not tell me, or am I imagining the whole thing?

I will say that when I picked the car up this last time, both the service writer and the service manager were "over the top" nice to me, nicer then usual, waaay nicer, They BOTH talked about how "easy a customer" I am to work with, and thanked me profusely for my business, even "hoping" I would come back again.

Now maybe they were just soliciting my further business since the warranty is about to run out, or....

 

Now that everything seems to be sorted out I suggest that you discontinue the battery tender routine. The reason I suggest this is as follows:

I have a spare Jag battery that I picked up cheep from a guy scrapping out his XJ. I had it load tested at the auto parts store and it checked out as new. I took it home, charged it up fully and put it on the shelf. Every 90 days or when I think of it I put it on the battery minder for a few days till it comes up to 100%
.
Now this is the important part ---- If I put the battery minder back on after a few days. even knowing that the battery is for all practical purposes still fully charged, the battery tender will still charge up the battery for some short period, no matter what.
I suspect that the battery tender is designed to "work" for some minimum period at a low level no matter the condition of the battery. This could be what your battery tender is doing. BTW I am using the term "battery tender" generically as there are many brands out there that do the same thing.

Also, there is nothing in your story that indicates your cars and their use is unusually taxing on a battery and you are experiencing the same issue with your other car/batteries.

Anyway, give my idea a try and let us know how it works out..

 

Sounds like good advice and it would seem to make sense that the tender is going to charge the battery to some level as it "decides" how much juice the battery actually needs. I guess that on a fully charged battery this could introduce the posibility of an overcharged condition.

 

I have an xtreme charger. Much better technology than the battery tender.