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There versions of hybrid-electric vehicle propulsion systems are currently
evaluated under different programs. The “Series Hybrid Electric Drive
(HED)” decouples the diesel engine from the wheels, driving each axel
or wheel by an electrical motor. Typical examples of Series HED are
the AHED and
SEP combat vehicles, developed for future armored vehicle
programs, and the future tactical truck (FTTV). This configuration is
viewed as more suitable for weapon carriers, missile launchers (such
as HIMARS, LOSAT, Patriot and MEADS). Elimination of the heavy
mechanical drive train reduces the total weight of the vehicle and
enables more flexible "packaging" of a mission system. Further
advantage is the ability to be stationed on "silent watch" for
extended periods or driven in "stealth" movement (battery powered).
This feature is absent from comercial 'hybrid cars' applications, due
to the high cost of battery and motors, required for extended
propulsion of the vehicle.
The “parallel hybrid electric” retains the mechanical link from the
engine to the wheels and augments it with electrical power regenerated
when the vehicle is braking or decelerates. A “hybrid hydraulic”
mechanism stores energy in hydraulic recuperators, rather than
chemical batteries. Although parallel hybrid is heavier than serial
HED, it offers the redundancy advantage of a conventional, mechanical
link when operating a heavy duty truck. HED can be applied into
existing vehicles ("plug-in" – Humvee,
HEMTT-A3, FMTV) or implemented
in the basic design of new vehicles (RST-V, FTTS,
FCS)
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