What Battery Capacity Do I Need to Run a Diesel Air Heater Overnight?

One welcome feature of a diesel air heater is that its electrical draw is small compared with its heating output. Most of the energy released comes from the diesel itself, while the fan, pump, and electronics sip a few tens of watts from the battery. Even so, leaving the engine off for ten hours puts real strain on a single battery, and sizing the bank correctly prevents a flat start in the morning.

Estimate the Average Power Draw

During warm-up, a 2 kilowatt 12 volt heater may draw around 35 to 45 watts while the glow plug and fan both work. Once the chamber is lit and the unit modulates, the draw typically settles near 20 to 30 watts, which translates to roughly 2 to 2.5 amps at 12 volts. A 24 volt version halves the current for the same power. Over a ten-hour night at an average 2.5 amps, the unit consumes about 25 amp hours.

Apply the Depth-of-Discharge Rule

Lead acid batteries should not be drained below 50 percent of their rated capacity if you want them to last several years. Using the 25 amp hour figure above, plan for a usable reserve of at least 50 amp hours, which means a single 100 amp hour deep cycle battery is a reasonable minimum for overnight 12 volt use. Trucks with twin 100 amp hour chassis batteries usually have ample reserve, though drawing them down deeply without a chance to recharge shortens their life.

Add a Battery Monitor and Recharge Plan

A small battery voltage monitor wired across the terminals removes guesswork. Most heaters shut down automatically when the supply drops near 11.5 volts on a 12 volt system to leave enough cranking energy, but relying on that cutoff every night accelerates battery aging. Aim to drive for at least an hour after an overnight run, or charge the battery from shore power when parked, so the bank returns to a full state before the next cold spell.

References

GB/T 7714: YEK P N Y, LAU C E, LAU S Y, et al. A novel microwave air heater integrated with thermal energy storage [J]. International Journal of Energy Research, 2022, 46(13): 19269-19277.

APA 7th: Yek, P. N. Y., Lau, C. E., Lau, S. Y., et al. (2022). A novel microwave air heater integrated with thermal energy storage. International Journal of Energy Research, 46(13), 19269-19277.

MLA 9th: Yek, P. N. Y., et al. "A Novel Microwave Air Heater Integrated with Thermal Energy Storage." International Journal of Energy Research, vol. 46, no. 13, 2022, pp. 19269-19277.