Just about got to work after 20 miles riding, slowed down to a stop, engine died. hit the starter button, battery barely turned the engine over. I pulled over, tried again, nop, no go.
Phoned ebike breakdown service, RAC van arrives 40 minutes later. I said to the guy, I think it must be the alternator, so I hit the button and it starts
he suggests checking the voltage, engine off, seat off ( cigarette socket fitteed under here) 12,5 volts showing, bike starts........... again
rev the bike 14 odd volts showing.
he follows me half way home, i get home, engine off. Tried to start it, slow cranking of engine.
I've just bought a new battery and have waited for the acid to be absorbed by the glass matt as per instructions. left it on the Optimate charger, which showed "charges" about 30 minutes ago. I'll check the voltage in another 30 minutes, if it's OK, then I'll see if the burger starts.
Still a bit confused why the engine died in the first place though.
I did hace carb icing on the way in, but for me ( at least) this has never manifested itself as a slow engine problem, only when cruising at a constant throttle, then hesitating when opening the throttle.
See what happens in a few minutes then.