So wife's run start isn't working. Dealer says both batteries bad and quoted nearly $500 to replace the small one.Laughing my butt off on that one. Anybody know what group size thatthing is for a 13? The other battery is less than a year old so it is under the man. warranty.

 

If you're from north America, unfortunately the only way of getting the same battery is through the dealer. Its an Exide EK151, which is only about £60! I live in Vancouver and they want 300 for the battery itself. Been trying to find a non oem direct fit but no luck yet! Keep us posted!

 

>So wife's run start isn't working.
And that bad, how?
It is the most useless advance in automotive design since, well, since anything else. Totally annoying and it really doesn't save anything in real world driving.
===================================
Angle parked in a parallel universe

 

^the problem is, according to the techs at jaguar/land rover that was working on my car, the secondary battery is not just a start/stop batter, it's used as an auxiliary battery as well, (like my brother's sl55). My Subwoofer would randomly not work upon start-up but after a few mins it'll work again, the first thing they checked was my secondary battery and then my primary which was slowly losing voltage.

It kind of makes sense too, my main battery is replaced but since my secondary batter is dead, my main battery needed charging, even though its less than a year old. Same case as OP, his secondary battery had failed and his is primary has failed too, so isn't it safe to assume that the secondary batter is required for other electrical components that the main battery alone cannot handle?

I really don't know, im just spit balling here and using my own experience as an example but I can't say for sure.

 

Yeah I'm tending to think that the aux battery being below 12 is putting a hurt on the other battery. Deka batteries typically don't fail like your average POS Interstate esp in 18 months time. Anybody replace the thing with another kind of battery that fit?

 

As Zamir advised it's an Exide EK151, others before have asked about some other replacement for it, and no-one to my knowledge has ever found one.
BUT you should be able to do what I did on the F-Type the first day I got it home - permanently disable the useless and incredibly annoying stop/start system (I agree with pab!) without effecting anything else in any way.
Simply unbolt the end of the earth lead which runs from the negative terminal of the secondary battery to a bolt in the bottom of the trunk/boot, and tie that end up out of the way with a cable tie so it can no longer touch the body.
I have been running the F-Type for 31 months now this way with zero problems and I have never had a battery or electrical issue despite it still running on the OEM battery for well over four years and 51,000 km now.
This fix is very quick and easy, or else you could simply remove the secondary battery altogether.
Also, you really don't need the secondary battery as a "supplement" for the main battery, once the stop/start system is permanently disabled it doesn't work that way.
After much debate and research on this and other forums it has been worked out that all the secondary battery does is for a second or so provide power to the peripherals (sound system, lights, HVAC etc) during a stop/start restart of the engine, to ensure the main battery has all the power (amps) it needs to start the car. Then, once the car has been restarted, the main battery takes over powering the peripherals again and the secondary battery goes back to sleep again.

 

I call it the spend a dollar to save a penny advancement. Whatever miniscule fuel savings you might gain is quickly eaten up by starter and battery replacements and addition engine wear from the constant starting. Don't most cars have a button to shut the system off?

 

Yep, most have an off button, including Jags.
But at least on Jags and I believe almost all others the system defaults to "on" every time you (as opposed to the system itself) restart the car, so it soon turns into a chore to remember to hit that button every time you start the car. And of course if you forget to hit the button the damnable system shuts down the engine just when you least expect it. Muuuch better to permanently disable it so you never have to worry about it again.
One more thing - it makes even less sense on a GT / sports car like the F-Type than it does on a saloon or SUV, especially if you want to get the jump on someone when taking off from a traffic light. I have read (never experienced it myself coz I disabled the system on day 1) that there is what seems like an interminable delay when trying to take off quickly while the engine restarts.

 

you didnt understand his statement or he didnt explain correctly. The small battery runs electrical function when in eco mode and engine off. Ask anyone who has disc this battery to disable the eco function. Nothing happens other than eco fail warning. And on the original poster that $500 may have included not only the battery but software update and or battery junction box which fail also and when testing you find that it was the contributor to the battery failure because it doesnt charge properly. But i didnt see the est. Yeah theyre exp either way considering its a 200amp riding mower battery.

 

^ yeah, you guys are right, I'm going to jist completely disable it. Afterall, i kept turning it off everytime i start the car.

 

Naw, the $500 was just for the battery. Replaced with a motorcycle AGM battery with 220amps, same size and everything. Just needed to replace the cables. All for less than $100. Only hiccup is the battery is a sealed battery (not vented at all so I need to change the vent set up. Still I refer to the stupid thing as an Obama Battery as the car would never see even $100 savings in gas over 5 years. Gotta love gov't fixes.

I will note that the eco mode is even more annoying now that the battery is sitting at 13 volts resting. At least when it isn't running I don't have to hear the sound of that tractor V6.