That's it - the engine computer is too concerned with not overcharging and makes no allowance for colder countries. We don't drive far enough to keep the vehicle batteries charged in winter. Left a dome light on last night, its 20 below C and the Black and Decker smart charger is pouring 20 amps into the battery at 16 volts. The engine never goes over 14.4.
A DC to DC voltage step up device is probably necessary to get effective charging from the engine. Or powerful lights to illuminate the solar panels.
Incidentally, it is confusing to see "amps per hour" in these pages. Amps are already coulombs per hour. Amp hours per hour would make sense but the hours cancel out to make plain "amps".
