..hawk, concerning this batteries:
-changed to this type, scooters (KYMCO LIKE 200i, XC 500i, XC 300iR, YAGER 150,....) assuming their modern regulators would (in association with batteries internal BMS [battery management system] to keep them charged, and it was like that. Especially the bigger i-models are picky about start-voltage.
-changed on a YAMAHA 650, MOTO GUZZI V35, MOTO GUZZI Nevada 750, MOTO GUZZI V65 to this type AND even the "old" regulators (see pics) handled and are handling charging pretty well. We are NOT having low freezing temperatures here, not below minus 2°C.
All cycles start in this temps, if you use the "twenty second battery warmup trick", ignition on, headlight on, 20', light off, start.
Initial reason for that WAS the XC 500s pecularities for starting voltage. On the others just because people (me included) don't want to think about battery care anymore.
Take the biggest mountable possible in all vessels.