Thank you very much. I’d be willing to bet my battery is low. I will definitely look into the CTEK unit! During winter I keep a trickle chargers on my other cars, so adding one more shouldn't terribly affect my electric bill... : )

 

Just do what heaps of us have done on early F-Types with the two battery system - follow the earth lead which runs from the negative terminal of the second battery to where it bolts to the floor of the trunk. Undo that nut (13 mm??), pull the cable off the bolt, and zip tie the end up out of the way so it cannot contact the body work (and put the nut back on the bolt for if/when you ever want to reconnect the cable eg you are selling the car).
This permanently disables the SS system with absolutely no effect an anything else.
I did this over three years ago and zero problems, the one thing I don't know is the state of the second battery, it could be dead flat by now for all I know.
I have considered removing the second battery entirely (saves about 15 lb apparently) but it's a real PITA to get at the rear mounting bolt(s) without ripping out half the plastic trim in the hatch so I haven't bothered.

 

I thought about that for a while but obviously came to the wrong conclusion. Since my system is permanently disabled the only time I see the yellow light is for a period of about 10 seconds immediately after starting the engine - and it then extinguishes. I assumed that the light was telling me that the ECO system was found to be inoperative.

So please clarify: those who do allow the start/stop system to work its irritating magic at every stoplight see the yellow light illuminated ALWAYS? - because the light is on if the system is operative?

 

I'm not quite in that category, but I'll answer. The light is on when start/stop is active. I disable via switch as part of my startup procedure. I don't drive until the fast idle drops, and that gives me time to buckle up, disable eco, and engage dynamic mode. I haven't disabled ECO because there are some situations where it works well for me. In those cases, I enable it manually for the duration of that benefit.

I don't really understand what's so hard about learning to push just one more button when I get in the car, but others may find the things that annoy me incomprehensible.

 

2019 base manual.... my eco has never worked properly. The light is illuminated orange/amber at start up, but in the top left of my control cluster LCD screen, you see the ECO logo with a cross through it. It doesn't show all the time, but intermittently. When I come to a stop, whether in gear or not, ECO mode never shuts down the engine. The other day it did it once, and I freaked out because it's probably the only time its happened since taking this new one. What's more, after an over the air update to the software, I lost lane departure warning, and a bunch of autonomous safety features. Back to the shop. Super fun.