How Much Power Does a Vertical All-in-One Diesel Air Heater Draw During Warm-Up?

Owners planning battery use for a vertical all-in-one diesel air heater often focus on running consumption, yet the warm-up phase draws the heaviest electrical load. Understanding that peak current helps size cables, batteries, and chargers so the heater starts reliably even after a long cold night.

The Warm-Up Current Spike

During preheat, the glow plug is energized while the combustion fan and cabin fan both spin up. A typical 12 volt 5 kilowatt unit may draw 35 to 45 watts at this stage, equivalent to around 3 to 4 amps. A 24 volt version draws roughly half that current for the same power. This peak lasts only about 30 to 90 seconds until the flame establishes itself.

Steady-State and Modulation Draw

Once the chamber is lit, the glow plug switches off and the current drops sharply to around 15 to 30 watts, depending on fan speed. As the thermostat modulates the heater down after the cab reaches temperature, the fan slows and consumption falls further. The average draw across a full night is therefore much lower than the warm-up spike, usually around 20 watts or so.

Planning Cables and Batteries Around the Peak

Size the supply cables for the warm-up current, not the average, to avoid voltage drops that cause aborted starts. Thin or long cables sag under peak load and leave the glow plug underpowered. The battery must also handle that initial burst, which is why a tired battery fails most often at the first morning start rather than during a steady overnight run. A brief engine charge after a cold morning warm-up restores the amps drawn during this peak. A small battery monitor fitted near the cab displays the live voltage, so the driver can see the brief dip during glow preheat and confirm it recovers after ignition. If the reading sags below the expected band, the battery or the supply cable is due for attention before the coldest weather arrives and weakens the starting cycle further.

References

GB/T 7714: GUO R, LI L, SUN Z, et al. An integrated thermal management strategy for cabin and battery heating in range-extended electric vehicles under low-temperature conditions [J]. Applied Thermal Engineering, 2023, 228: 120502.

APA 7th: Guo, R., Li, L., Sun, Z., & Xue, X. (2023). An integrated thermal management strategy for cabin and battery heating in range-extended electric vehicles under low-temperature conditions. Applied Thermal Engineering, 228, 120502.

MLA 9th: Guo, R., et al. "An Integrated Thermal Management Strategy for Cabin and Battery Heating in Range-Extended Electric Vehicles under Low-Temperature Conditions." Applied Thermal Engineering, vol. 228, p. 120502.