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Aura Systems Introduces Hybrid APU for Long-Haul Trucks

Aura Systems has introduced a hybrid APU system for long-haul trucks that combines a small generator engine with an auxiliary battery pack.

The AuraGen ICS hybrid APU system (“Gen-a-Sys”) provides continuous electric power of up to 5 kW of electricity with the APU engine running and 3 kW when the APU engine is off. The driver activates the system by a push of a button mounted next to the steering wheel.

When the APU engine is turned off, the system draws power from the auxiliary battery pack that is sized to meet the operating time required by the customer. The system automatically monitors the batteries’ charge. When the batteries’ charge is low, the APU small engine automatically turns on and recharges the batteries using an optimum charging methodology. As soon as the batteries are charged, the APU engine automatically turns off and the system seamlessly returns to engine-off mode.

The AuraGen patented Bi-Directional Power Supply enables the seamless transition from battery power to APU-engine-generated power automatically. Unlike other systems, the APU engine is only used during low battery power levels.

Devices such as engine pre-warmers, air conditioners or heaters, refrigerators, microwave ovens, and televisions can all be used without idling the truck engine. This reduces fuel consumption and emissions during rest stops or while waiting for loading or unloading without sacrificing driver comfort.


Sid Hoffman

I wish they would have listed an estimated ROI. Obviously the idea is that the hybrid APU uses less fuel than running the engine, but without knowing how much less it takes, there's no way of knowing how many years of service would be needed for the fuel savings to cover the cost of the APU.


With anti-idling laws becoming common it will soon be irrelevant what the ROI is compared to idling the main engine. The relevant comparison will simply be which APU or alternative "hotel load" system is most cost effective.


I'd like to see some data on the emissions of the genset vs the emissions of idling.

A lawn mower produces more emissions (HC, Nox etc) in 1 hr than a moder car does in 100,000 mi.

A small engien may have a service life of a few thousand hrs over which its emissions get worse as parts wear out, a 11, 13, 16L OTR truck engine may have a service life of < 20,000 hrs.

I know they mean well, but depending on how the system is implemented it could be counterproductive.


Well you have to look at a few things here:

1. The industry stated goal for APUs is to provide a 24 month payback period. When maintenance costs for the APU versus the reduced maintenance costs for the main engine are included this is a reasonable goal.
2. SAE paper 2003-01-0289 shows APUs provide lower emissions (NOx is something like 7% of what is produced by idling the truck). This is of course from 2003.
3. The above two items are arrived at using an APU that runs constantly and not one which runs intermittently as described in this article (constant running does provide the benefit of keeping the engine coolant warm if the APU is integrated into the main cooling system which allows for easy start up of the main engine while providing warm air for the passenger compartment).


I'm ready to buy one. I'll build my own hybrid.

Get 500 mpg.

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