Battery HVAC
Battery-powered heating, ventilation, and air conditioning (HVAC) systems help fleets deal with cab climate control, by providing climate control to the truck cabin while the truck is parked. Fleet users benefit because the systems are quiet and produce no emissions, but they may not provide enough cooling capacity for long rest periods or when operating in very hot temperatures.
They can be powered by a set of batteries on the tractor or come with a plug-in capability for battery charging and/or operation while connected to an electrical power source. They are also called battery APUs and battery EPUs.
Benefits
Zero Emissions
No emissions produced during operation
Fuel Cost Reduction
Since they do not burn fuel there is no fuel cost while they are in use.
Lower Purchase Price
Less expensive than some other anti-idling options.
Quiet Operation
Quieter than diesel APUs.
Less Maintenance
Fewer moving parts so less opportunity for malfunction and less maintenance training than diesel APUs.
Integrate with Off-board AC Power Connection
This will increase the operating time of the unit and will also recharge the batteries more cheaply than doing so with the engine alternator.
Easy to Operate
Digital or rotational automotive-style controls provide automatic temperature control. The driver simply turns the switch to heating or air conditioning, and selects a fan speed and a desired temperature.
Challenges
Limited Run Time
Not a viable solution for the 34 consecutive hours of rest without restarting the truck’s main engine and running it from time to time. In most cases, however, the batteries of the battery HVAC system will simply be recharged while the truck is driving.
Issues in Hot Temperatures
Concern that in extremely hot conditions there will not be enough battery power to keep the sleeper/cab cool enough for the driver to be comfortable.
Battery Replacement
The AGM batteries in these units do not last forever and will have to be replaced. Two years seems to be the typical life expectancy of these batteries.
Added Weight
Including the required four deep-cycle AGM batteries and a fuel-fired bunk heater, battery HVACs will add 500 to 600 lbs. to the weight of the vehicle. This may become less of an issue in the future if other battery technology is developed. However, the Energy Policy Act of 2005 allowed for a national 400-pound exemption for the additional weight of idling reduction technologies on heavy-duty vehicles. In 2012 the Moving Ahead for Progress in the 21st Century Act increased the weight allowance to 550 lbs. However, each state can adopt the exemption at its own discretion and not all states have. The Office of Energy Efficiency & Renewable Energy has a map showing states that recognize the APU weight exception.
Need for Large Capacity Alternator
The increased load battery HVACs place on the charging system means a large capacity alternator is needed. Cables of the proper size also must be used, and it is important that all connections be tightened properly for the system to operate.
Adds Load to the Engine
The alternator for a battery HVAC system puts twice the load on the engine of a normal sleeper tractor’s alternator. These higher capacity alternators take up to an additional 7 hp from the engine. Therefore, their use does cause a truck to consume slightly more diesel fuel while driving, but lowers fuel use overall as they can eliminate significant amounts of idling.
Can Consume Fuel
Systems equipped with fuel-operated heaters will consume diesel fuel during heater operation as well as battery or AC power to run the heater fan.