Before you know it, we're back down to 68% charge. With 100km to go before the next stop (a Lidl at Besancon). What's more, we've got a climb. Up, up and away across part of the Jura.
We'll be crossing the border from Switzerland into France at Vallorbe.
But as we climb up the long motorway drag to the frontier, the percentage charge is falling – even with the REx chugging away in the back.
"Are we going to be able to get up and over? If the range is dropping so quickly?" Is that the whisper of range anxiety I hear? Even from an i3 REx owner.
"Don't worry," I reply with the seasoned confidence of someone who has been across this mountain pass once before. "We'll be fine."
But will we?
To be continued …