I knew the traction battery was charged to about 80%
So the 12V battery must have been drained.
Luckily I have an old battery charger that was pushed into service
Left for a couple of hours, this was able to charge the 12V and I was able to start the car.
In the meanwhile I’d called my dealer who suggested bringing the car in to have the battery checked. Or I could call Honda Assistance.
I took the car in. Battery checked. No problems
Their e engineer suggested the issue was that I had not “turned the car on”, so was just pumping up the tyres via the 12V battery. If I’d turned the car on, then charge from the traction battery would have recharged the 12V battery. Hmmm
Thoughts? On the one hand it makes sense - a bit like running an ICE to run the alternator to charge the 12V. But on the other hand, why doesn’t the traction battery just trickle charge the 12V anyway?
I will keep you posted and appreciate any views
Happy New Year