Battery-Swapping Heavy Trucks Need Thermal Management Too

January, 2:00 a.m., at a battery swap station. A driver, working his second night shift of the week, slowly pulls his truck into the station; the gantry crane operates automatically; about five minutes later, the vehicle is fitted with a fully charged battery and drives away. From the perspective of logistics efficiency, this process is nearly flawless. However, when the driver turns on the cabin heater and watches the windshield gradually fog up, he realizes that those five minutes of “efficient” battery swapping haven’t solved the dilemma he faces.

While the battery-swapping model eliminates charging wait times, it cannot eliminate the impact of temperature. We often emphasize this point to fleet engineers—usually during the first winter after a battery-swapping project goes live, once the technical specifications have been finalized. The thermal management challenge hasn’t disappeared; it has merely been “shifted”: part of the burden has been transferred to the battery swap stations, while the other part remains with the truck. And the portion that stays on the truck is often overlooked.

For plug-in trucks, the battery typically remains on the vehicle and is slowly charged overnight. In contrast, batteries in battery-swapping systems face a far harsher “living” environment: they are rapidly charged at a swapping station, installed in a truck to complete a shift, then swapped out, only to enter the next round of rapid charging. Currently, standardized battery packs used in heavy-duty trucks exceed 400 kWh in capacity, with existing designs reaching as high as 432 kWh and 513 kWh. Charging such high-capacity batteries at the rates required for commercial operations inevitably generates heat—heat that ultimately becomes a problem for battery-swapping stations to address.

The same applies to low-temperature issues.

If a battery is left idle on an unheated storage rack on a winter night, charging speeds slow down, and the battery ages more rapidly during this process. At low temperatures, battery cells struggle to accept a charge; forcing a charge comes at the expense of the battery’s cycle life. Consequently, battery swap stations must assume the thermal management responsibilities that would otherwise fall to the trucks: maintaining the batteries within an appropriate temperature range—preheating them before the morning rush hour and cooling them during the afternoon charging peak. This thermal management capability must be incorporated into the design of battery swap stations and configured to meet the demands of peak hours. If designed based solely on average conditions, by 6:00 a.m., the swap station is likely to be filled with a pile of “frozen” batteries, causing vehicles to line up and wait.

The cab doesn’t go into the storage rack along with the battery. In temperatures as low as minus 20 degrees Celsius, drivers need warm air for heating and a clear view through the windshield; a battery maintained at the “swap station ambient temperature” does nothing to address these needs. For battery-swap trucks, cab heating is just as “routine” a task as it is for any heavy-duty electric truck: equipping the vehicle’s own cooling circuit with a high-voltage coolant heater—taking our company’s Q-series products as an example, their power ranges from 15 to 35 kW, with voltages spanning 400 to 1,100 V.

The temperature of the battery pack also fluctuates. When the battery pack leaves the battery swap station, its temperature is still within the ideal range, but it subsequently undergoes prolonged operation at low temperatures. As the temperature drops, available power decreases accordingly; therefore, the truck must have sufficient onboard heating capacity to ensure the battery pack remains within the normal operating temperature range until the next battery swap. If vehicle configurators mistakenly believe that battery swap stations can solve all thermal management issues, they will discover during a nighttime operation in January that this is not the case—we would prefer they realize this during the planning phase rather than waiting until actual operation to find out.

For plug-in trucks, the cooling circuit is typically a closed system that requires no external connections; for battery-swap trucks, however, if fluid connectors are incorporated into the design, these connectors undergo repeated plugging and unplugging every day—often in environments filled with dust and sand, subject to freezing temperatures, or under time-sensitive conditions. Each insertion and removal cycle causes wear on the seals, tests the performance of the self-sealing valves, and may allow air to enter the circuit. In trucks with closed cooling systems, air locks in the cooling circuit might occur only once every ten years, but in battery-swap fleets, this becomes the norm.

Anyone responsible for planning battery-swap vehicles should develop three habits: First, require suppliers to specify the insertion and removal cycle life of connectors in writing; second, design coolant refilling and venting procedures tailored to the operating environment of battery-swap stations (rather than repair shops); and third, incorporate coolant condition monitoring into the key performance indicators (KPIs) for battery-swap stations. In a battery-swapping network, the reliability of thermal management depends largely on standardized management at the interface—after all, when problems arise, people tend to blame the battery chemistry itself.

Take operating conditions in January as an example: To conserve energy, battery-swapping stations maintain battery packs at low temperatures overnight; consequently, when a battery pack is installed in a truck, its temperature is only −15°C. At this point, although the truck had sufficient battery charge, it could not perform at full capacity: discharge power was limited, energy recovery (braking) was restricted, and rapid recharging was not possible until the battery pack warmed up to an appropriate temperature. Although the battery swap itself takes only five minutes, the resulting performance limitations can last for about two hours.

If the battery pack were preheated using grid power at the battery-swapping station prior to the swap, it would not only be more cost-effective but also avoid taking up the truck’s actual operational time. For this reason, battery-swapping agreements must include “thermal management clauses” that clearly specify the battery pack temperature at the time of handover and hold the battery-swapping station operator responsible for meeting this target. Early battery-swapping contracts often overlooked this point, and the cost of neglecting it can be extremely high.

If a fleet operator were to submit a battery-swapping technical specification to us tomorrow, we would prioritize reviewing the following five items:

• The temperature control capabilities (heating and cooling) of the battery-swapping station should be sufficient to meet battery-swapping demand during peak hours.
• The temperature range at the time of battery pack handover should be clearly specified in the operating agreement.
• Trucks should be equipped with an independent coolant heating system for cabin heating, defrosting, and maintaining battery pack temperature; this system should operate independently of the battery swap station.
• Specify the cycle life metrics for coolant connectors (quick-connect fittings), as well as the procedures for draining and refilling coolant at the battery swap station.
• Record the temperature data for each battery pack during every cycle and incorporate it into the fleet’s key performance indicators (KPIs) for evaluation.

Battery swapping is an effective solution to the problem of lengthy charging times, but it does not address temperature-related challenges. Projects that attempt to solve temperature issues through battery swapping often end up having to retrofit heating systems by the second winter.

No. The need for cabin heating and defrosting remains unchanged, and the vehicle still requires heating while driving to maintain the battery pack’s temperature. Battery swap stations are responsible only for temperature control related to charging, not for the full range of thermal management required for vehicle operation in winter.

It can replace pre-departure preheating and temperature control during charging, but it cannot maintain the battery pack’s temperature under prolonged cold conditions. Both components of this system—temperature control at the swap station and the onboard heater—are necessary.

This is a commercial issue, but it must be clearly defined in the contract and listed alongside the handover temperature provisions. Compared to the battery cycle life protected and the downtime avoided, the energy consumption for battery pack heating is negligible.

Are you planning to develop battery-swap vehicles or battery-swap stations? Please provide us with the operating cycles, environmental conditions, and battery pack specifications. We will calculate the required capacity of the on-board heating system for you and outline the thermal management requirements for the battery-swap station that need to be specified in the relevant agreements.