Hi I am currently facing two issues:
1) Green eco rarely turns on and if it does, it works for short period of time
2) When I stop and have no need to have engine running and turn it off while having heated seats on, listening to music or charging my phone(from back 12v port) it shuts down stuff quickly. Longest it can hold is 10-15 minutes.

Can anyone give me crash course what each individual battery is for?
I am assuming either they need to be charged or need to be replaced. I just need to know which can cause issues mentioned above, if not both.

 

The quick answer is replace main battery, there are many threads on this sight to help you understand better how this charging system works, it's pretty complicated and it also changed by model year, you mentioned facelift so I assume '14-'16 so you have a main battery under the hood which runs things when your driving and another in the trunk which takes over when your in eco-start stop. there are I believe a long list of parameters the car must meet for start-stop to engage regularly, this forum is your friend!

You might want to check both batteries to see if their ok though.

 

Just charge your battery. I'm in the same position as my battery is around 6 years old. Once I charge it the eco/stop comes back. I don't drive long distances otherwise the eco mode would work itself.

 

Regardless of whether your battery needs a charge top up or is going flat on you, these guys are correct in that your eco start-stop needs a strong MAIN battery to function. Charge or replace and your eco S/S will come on very quickly once the parameters are satisfied.

 

ECO hardly becoming available is a sign your main battery can not reliably power your car during "Engine Cut Off" cycles. The ECU recognizes that condition and disables ECO stops.

There are multiple reasons a low-battery can happen including an old tired or a drained battery either while parked or driving.

What's the mfg date code on your current battery: less than 3Yr or more than 5Yr ?

SHORTCUT:
You can replace your batteries now then figure out details later.

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Charging your main battery will help as I did this for about a year before developing other electrical gremlins like window switches not working or getting errors on dash. If your battery is older than 4-5 years save yourself a headache and replace your battery.

 

Thanks everyone, I changed my main battery which was manufactured in 2018, new one is same model and works like charm.

 

Another victim of whacky yoyo ECM based charging....

 

Tested on long distance today. Green eco works fine but is extremely annoying but that was what I was asking for 😆

 

Glad our gang could be of help for your concerns.
We like satisfied owners without headaches.

 

Ha! Yes, bothers us when it doesn't work, and bothers us when it does.