Cold-soaked batteries, heat pumps and DC fast charging: the thermal chain

A technical reading guide for Canadian winters, using overseas BYD engineering disclosures, Canadian owner manuals and independent test context

Data snapshot: October 13, 2026. Independent research; not a manufacturer website or buying advice.

A parked battery and a cold cabin are not the same problem

After sitting outside overnight, a battery may be colder than its preferred temperature for power delivery and charging. Meanwhile, passengers need cabin heat. Heating the cabin is about comfort and energy use; battery thermal conditioning is about the pack’s operating window. A car can support one form of preheating without offering every form of automatic fast-charge preconditioning. Check the owner manual for the exact model and year.

Departure preheating while plugged in shifts the energy source

Natural Resources Canada’s 2025 fleet guide recommends a 20–30-minute plugged-in preheat where applicable. This can warm the cabin and battery before departure so that less heating energy must be taken from the traction battery during the opening part of the drive. The recommendation is general operating guidance, not a measured range improvement for every EV. Timers, charging power and whether battery heating is supported vary by vehicle.

Battery preconditioning ahead of a charger has a different objective

Hyundai Canada’s IONIQ 5 manual describes battery conditioning that can be activated manually or through navigation to a DC charger, but only on an equipped vehicle and subject to battery state and temperature. It may consume energy and time before arrival. In Tesla’s owner documentation, route-based preparation similarly anticipates Supercharging. A cold pack can be charge-limited even at an otherwise powerful station, so “350 kW charger” does not mean the vehicle will draw 350 kW.

BYD’s heat-pump claim explains hardware, not a Canadian winter score

BYD’s European SEAL documentation describes a wide-temperature heat pump, battery direct heating/cooling and drivetrain waste-heat recovery, with a stated −30°C to 60°C operating envelope. This is the manufacturer’s engineering disclosure for an overseas configuration. It is not proof of a fixed winter range, a specified fast-charge time at −30°C or a confirmed Canadian SEAL trim. A heat pump primarily helps cabin thermal efficiency; the battery still requires its own temperature management.

What a reproducible winter DC-charging test must record

A useful test identifies the exact year and trim, the starting battery temperature or cold-soak period, ambient temperature, starting state of charge, whether routing triggered battery conditioning, charger rated power, measured charging curve, 10–80% time and actual energy delivered. The 2025 CAA study and Norwegian NAF archives provide valuable but differently designed observations. They cannot be converted into a Canada-specific BYD result by applying another car’s range-loss percentage.