Happy to sell mine, its just sitting on a shelf in my garage - will never go back in my car. 2015 R

 

Bump. Did this ever get resolved or are we still on the "must buy from Dealer" verdict? Im nervous about simply unplugging it and leaving it as is, are you guys sure it *only* handles the start / stop feature and nothing else?

 

I recently installed one of these :

https://www.ebay.com/itm/Battery-Aut...rd!95051!US!-1

The group size for these batteries is AUX14. In the UK there's an Exide battery, p/n EK151, available easily with the right posts, but here the Deka AUX14 seems to be the closest match.

The only problem is that the terminals are threaded, instead of posts. I actually cut the posts off the old battery, drilled them out 6mm, and bolted them to the new battery.

The alternative approach would be to have two new battery cables made, with the right terminals at the battery end (M6 screws). I might still do this.

 

Just a note?
The small battery does NOT start the car. It's only function is to operate everything else except the starter when the car goes into start/stop mode.
No there is no downside to removing the small battery.
.
.
.

 

Long Post- A solution
I want to chime in on the sequence of events leading to the replacement of my auxiliary battery and some of the odd symptoms it was causing.
Two years ago the eco start/stop feature stopped working. Then one day after starting the vehicle there was a warning displayed over the tachometer upon starting to replace or recharge the battery. I bought a charger and charged the main group 49 H8 AGM battery. It was reading only 11.7 volts at the time which is very low. After charging, the warning light went away and the eco start/stop was working again.
Earlier this year the eco start/stop feature stopped working again. I replaced the main group 49 battery but it did not fix the problem. Instead after replacing the main battery I started getting a flickering of the headlights and instrument panel which would last a few seconds. I noticed some engine hesitation as well. This usually was when the car was in drive.

I was on a 1,000 mile trip in northern Nevada two months ago, during which I had a flicker on 4 different occasions. These would last about 5-10 seconds but were very scary. In all cases I was driving over 70 mph on states notoriously desolate 2-lane highways or I-80 . The lights and instrument panel would flicker. A series of faults showed up over the tachometer. First "ABS Fault", Then "Traction Control Fault" then "Cruise control cancelled". I was driving 80 mph on I-80 in northern Nevada with the cruise on and it deactivated the cruise control. I was not sure if the car was still operational. Were the turn signals working? What about the brakes, accelerator? I was about to pull over, but it eventually worked itself out and I was able to continue.
Upon returning to Las Vegas, I made an appointment at the dealer for 6 weeks later due to my work schedule to look into the matter and deactivate the automatic running headlights, a feature I hate. The service advisor did mention at the time of making the appointment that sometimes the smaller auxiliary battery needs to be changed as well.
I then tested the auxiliary battery, which was testing under 10 volts, and needed to be replaced.
I received two quotes of $340 and $332 for replacement batteries from the local Jaguar dealer and another one in Portland where I fly to for work. SInce this is a lawn tractor/motorcycle battery, I was looking for another less expensive solution.
I looked extensively online for a solution. There are many features with the Jaguar auxiliary battery that make finding a suitable replacement nearly impossible. This explains the frustrations many members are having.
I took note of the physical dimensions and terminal location of the original battery and other features like the indention on the top for the bracket holder. I then looked for a 12 volt AGM battery with 200 CCA. I found one that was 12 amp hours instead of the 14 on the OEM battery, I did not think that would make any difference. It does not have a vent hole near the positive terminal like the OEM.

The hard part was figuring out what to do with the terminals. Flag to post adapters are sold on a small number of sites and at O'Reilly's, which convert lawn tractor terminals to automotive posts. The holes on motorcycle battery terminals might allow for this type of adapter to be used.
After purchasing the adapters and a battery, I tried unsuccessfully to connect this. I took this to O'Reilly's and was able to get some bolts that were longer which allowed me to connect the post adapters at a 90 degree angle.

I then tried to connect this motorcycle battery with the new battery terminal adapters to the existing battery cables, but realized that these battery cables do not fit the new automotive post terminals. I then went to Autozone and purchased two new battery cables.
The positive battery cable does not fit securely at it's base however it is connected securely. Immediately after installation, I started the vehicle and the eco start/stop feature started working immediately. I took it to the dealership for the scheduled appointment the next day mentioning that the eco start/stop started working again after the battery was replaced. I still needed the running lights to be deactivated by the dealer. The service advisor mentioned that other customers have reported strange symptoms including problems with shifting, flickering of headlights and all of the faults and dashlights I was seeing. I even noticed problems with the radio information texts. For those of you who choose to not replace the auxiliary battery, you do this at your own peril.

Items purchased
1. Deka ETX14, Sigmas Tek AGM battery, From BatterySharks.com
12 volts, 12 ampere hour, 200 Cold Cranking Amps, Absorbent Glass Mat
Weight 9.43 lb (4.28kg)
LxWxH in inches 5.94 (151mm) x 3.43 (87mm) x 5.79 (147mm)
Product Code: BC-ETX14_M12-12-200-D, Model STX14-BS
Big Crank ETX14 Battery
1 x $28.65
Shipping Cost $10.95
$39.60
2. Flag to Post Terminal Adapters (2 adapters per pack), From BatteryMart.com
Item: DEK-02033
1 x $2.95 = $2.95
Shipping = $4.99
$7.94
3. Dorman Hex Bolt, Blister pack of 6, From O'reilly Auto Parts
Part Number 981-220D, 20mm length, 3/8" head
1 x $4.29
Sales Tax 8.25%
$4.64
4. Duralast Battery Cable (2), From Autozone
Part Number: DT412B
2 x $7.49 = $14.98
Sales tax 8.25%
$16.22

Total $68.40*
*Only replace with an AGM battery. Lead-acid batteries are not able to handle the demands.

 

Glad you got it working but the Jaguar dealer is clueless if he thinks that little battery can cause all that!!

You can easily prove this with a simple experiment. Unhook the negative terminal to the small battery. All done. You will never see the ECO function again. You will have no dash lights or any other symptoms.
We have had numerous members of this forum do that and it is a permanent solution to the entire ECO mess!
.
.
.

 

I guess it's possible that either a good aux battery, or no aux battery at all, would both work fine - but a wonky, half-dead aux battery could cause issues.

 

Exactly Mark SF, even on other cars I have driven a bad battery can cause the other electronics to operate strangely. On an old X-type I was driving 15 years ago Sport mode would not activate when the battery was nearing the end of its life. And on a Ford I drive as my daily driver the headlights were noticeably brighter and radio seek button which had malfunctioned operated properly once I replaced the battery.

It seems like the XJ knows what to do if the aux. battery is removed or in good shape. When the battery is at replacement but still has some voltage the car does not know how to handle this situation and thus the chaos. I have not any of the problems since replacing the aux. battery with my workaround solution. The eco start/stop feature is working fine and kept the engine off for 5 min. straight last night while waiting in line with the A/C off. Again my solution cost me only $68.40 in parts but several hours in reading and researching.

 

And finally, you can disconnect the start/stop small battery (its only function is to operate the start/stop system) without causing any problem at all. Unless your car is consistently operated in stop and go situations, this annoying ECO system offers very little advantage ecologically and significant irritation to many drivers. On my car this smaller battery was disconnected two years ago. No issues whatever, except that I am no longer annoyed by the stop/start!

 

hi my cable is disconnected and the yellow eco light comes on every time

 

Right, but just during the starting sequence, then goes off and doesn't come back on until restart. I can live with that, way less annoying than leaving the system active.

 

mine stays on all the time.

 

Same here, it is constantly ON. Also, a message, "Low Battery Voltage, Start Car", is now on the dashboard, even though the main battery tests like new. 2014 5.0L Supercharged is the car.

EDIT: Got an aux battery from WalMart, slaved it to the OEM battery cables and the ECO light went off. Now I'm going to have new cables made and that will be that. The low voltage message continues, but another thread has given me a process to clear the code.

 

Must be different systems?
I have experimented with mine and it does not keep the light on at all?
.
.
.

 

While it seems that our cars can differ in how the aux battery failure manifests itself, with mine the voltage was less than 1.0 when I got the car, the ECO light was always on, removing a cable didn't change anything, and then the "Low Battery, please start car", message appeared when I opened the door and continued until the car started.

The AGM battery came from Wal Mart (ES-TX14, $85 incl tax)


, exactly the same dimensions as the OEM Exide. Instead of messing with adapters for the clamps, a trip to NAPA got the Neg cable fitted with an eye, and a whole new cable for the POS because the original wasn't long enough to cut. $10 later, the cables were ready to fit to the battery. The final mod was to drill the vent hole larger than what was in the WM battery, using the OEM hole as a simple guide for size. Routed the vent hose to the rear of the new battery and the rest is history.
No lights, ECO works as it should. Total cost $95.

 

That's the second post where someone has installed a small AGM designed for small vehicles. This category of battery is not suitable, as it might not be able to handle the rapid charging requirements of a start/stop battery.

You need a battery specifically rated for start/stop applications, like the Exide EK151 or the Deka / East Penn Aux 14.

 

When are apples not apples? If both batteries are 200cca, 12V, and 14Ah, how do we find that extra bit of glitter in the EK151? I has to be measureable, and weight is the same, too.

 

Agreed, this battery seems pretty much identical to the OEM Exide EK 151 and it should work perfectly well as a direct replacement.
That said I disconnected the stop start battery on the F-Type the first day I got it home (3.3 years ago now) as I cannot abide the system and how it works (or not!) and I've never had a single battery or electrical system problem in all that time, and it still has the original now 5 years old main battery in it.

 

One of our cars is my bride's Lexus hybrid RX450h, and there is noticeable action when the engine turns Off and turns back On. With the new battery that killed the dashboard light on the XJL, if the Stop/Start system is working, then it is a pure delight, because we can't tell the difference. Light Off, and No change in performance manners = good news.

 

Let me again question your logic, and expertise, when you use words like, "small". Sounds like left-coast logic about other subjects that leaves facts in the rear-view mirror, doesn't it?