Went out without a mobile phone to do a bunch of iTunes app downloads on a fast semi-public wifi, one that's built into a public phone booth. I can access it because my home wifi is set up with a Fon & a Telstra Air hotspot, which in turn means I can access Telstra Air hotspots, be they public phones or similarly setup home routers like mine. My home broadband is billed for any usage.
I'd also taken a 12 - 240 volt inverter and the MBA charger, and topped up the MBA's battery whilst doing the downloads.
But I left it connected for too long & the car wouldn't start or would stall when I did start it. Grr. No mobile phone to call for help.
But wait! I'm at a public phone & the automobile association's roadside assist number is toll-free. So I'm standing at the phone booth trying to find my AA membership card. I knew it was somewhere in my wallet but it was proving elusive. So I returned to the car & spread the various cards out on the passenger seat & eventually found the thing.
I decided to give the car one more chance, it had been about 5 minutes since the last try & I was rewarded with a running engine.
I immediately headed off on a 58km round trip to buy the very special milk that I like & can only get at this one shop.
So the car has had a decently long run to charge up the battery. Two lessons learnt: 1: always take a mobile phone. 2: use the Lenmar Chug Plug https://www.amazon.com/ChugPlug-External-Battery-Portable-Adapters/dp/B00IIZOYFG/ref=sr11?ie=UTF8&qid=1482140720&sr=8-1&keywords=chug+plug+macbook+air with its internal battery instead depleting the car battery.