Mobile Installation In 2005 Toyota
Photos of the installation are
- The Prius main electric system is a 240 VDC MNiH
battery pack that powers a 440VAC 3-phase 60 Hp water-cooled electric
motor. (The electric motor is plumbed into the radiator just like the gas
engine.) A 240VDC to 440 VAC inverter is integral to the electric
motor. This HIGH-POWER DC-AC conversion creates LOTS of broadband white
noise on the HF bands (S9 plus on all bands 40 through 10 meters and
about S6 on 6 meters) which gets worse when you step on the brakes (Energy
is partly reclaimed by making the motor run backwards as a generator to
recharge the battery when you step on the brakes. Normally, the drag of
the motor-cum-generator provides nearly all the braking effect. Unless you
push the brakes all the way down in a panic stop, the mechanical brakes
and linings almost never engage. ).
The high white noise level makes HF operation (except for the extremely
strong signals of 15M and 10M band openings) nearly impossible. The noise shows up even at VHF where it
registers about S-1 or S-2 on the Kenwood D700's S-meter.
- The Prius 12 VDC system is a very vestigial
affair intended to power just the radio, lights and computer display. It
uses a 240VDC-to-12 VDC stepdown converter that can provide about 40-50A
but the 12 VDC battery is a 20 AH device that looks like it came from a
motorcycle. It's main purpose to power up the computer electronics that
need to boot in order to start the hybrid power system. (In the Prius,
EVERYTHING is fly-by-wire. The power steering, the water pump, the power
brakes and the air conditioning are all powered electrically off the 240 VDC system which in turn is controlled by the 12 VDC powered computer
In my install in a 2005 Prius, I installed a second 50AH deep-cycle
battery with an intelligent voltage-sensitive isolator to run the computer
and radios engine-off. The DC-DC converter has no problem charging the
second battery, especially because the power-FET-based Hellroaring
Technology battery isolator has inrush limitation. Details on the
Hellroaring isolator are here:
The isolator and second battery hookup is similar to the one shown on this
- I have observed no interference problems TO the
Prius' complex electronics FROM transmitters at all, even with 100W on HF or 2M.
- On the other hand, there is plenty of
interference FROM the hybrid power system TO the radios. Based on
my experience, it is almost useless to try to receive on a frequency below
about 2 meters in the Prius. On bands below 2M, receive is masked by a
continuous S9 white noise level. This is NOT discrete "birdies" such as
you get from computers or TV horizontal sweeps. It is broadband white
noise hiss that sounds exactly like an empty channel except at S9 instead
of S0, on any of the HF bands.
[ My hypothesis is that this is simple diode noise from the very
large amounts of DC current flowing through semiconductor junctions in the
hybrid power converter system; not switching transients from the DC-to-AC
power inverters which would tend to be harmonics of a discrete frequency
that would repeat every so many KHz as you dial across the band. ]
- When you park, but don't shut down the hybrid
power system (you don't start this car; rather you boot it), the gas
engine shuts down but the control systems remain live if you don't push
the "OFF" button.
In turn, you can continue to run the electrically-powered air-conditioning
or other devices from the 240 v battery. Every time the battery drops to
about 210 volts, the gas engine will start up by itself, run for a minute
or two to recharge the battery and then shut off again. It can repeat
this process endlessly. The 240-to-12VDC down converter continues to
run, making available 30 amps continuously. This is very handy when
operating mobile-at-halt for some special event, without having to
continuously idle the engine for power. I've actually slept overnight in
the car in air-conditioned comfort (in Iowa in August!) with the APRS
laptop and radio running, and used only about a half-gallon of gas.
- This has some interest emergency power
potential. The website
http://priups.com [ As in "Prius UPS"]
explains how many high-power computer-room UPS systems actually use 240
VDC batteries. By connecting one of these devices (without it's battery)
across the Prius 240V battery, you can extract a continuous 10-15KW of AC
power ( ! ) from the Prius elecrical system. Again, every time the battery
pack drops to 210 VDC or so, the gas engine just starts up and recharges
it. [And the Prius gas engine at idle is virtually silent unlike most
gas-powered generator sets.]
- A third-party adapter is available that can allow
the car's color LCD "multi-function" display to display external NTSC
video sources; i.e. a built-in monitor for my mobile SSTV LiveCAM.
Click on thumbnails for
full-size pictures. (Pictures open in separate windows.)
||View from driver's seat of mounted
control heads for Kenwood TM-D700 APRS radio and Yaesu FT-100 HF
transceiver. The laptop, running UIview and MapPoint, is supported by
a commercial Ram Mounts "RamPod" mounting system. This tripod system
uses soft-drawn 5/8 inch aluminum rods that can be bent by hand to fit any
installation. The bottom of the rods lock into brackets with setscrews
that slip under the seat rails.
||View of mounted control heads from
passenger side. There is a lot of room between the front of the
console and the underside of the dashboard for mounting hardware. Note
the GE mobile radio speaker mounted behind the radio control heads. The
device at the left is the tripod head and ball-joint of the RamPod mount for
The bracket, bent from .090" aluminum, is bolted to the underside of
the plastic dash with a single 1/4" bolt and nut. The screw head,
inside the dash, is re-enforced with a 2-inch diameter fender washer to
avoid cracking the plastic surface. The surface of the bracket that is
against the plastic dash has a piece of ribbed industrial rubber
matting glued to it to provide friction to prevent it from rotating.
to download a drawing with the dimensions of this bracket, in Acrobat .PDF
||View of the RamPod "foot" mount. This
view is of the left rail of the passenger seat. The seat is pushed all the
way to the rear to expose the hardware. Normally the aluminum rod is covered
with a piece of black cable loom for a more finished appearance. The
black box behind the rod is a DC-DC converter to provide 19VDC for the
laptop computer from the 12 VDC system.
||This is the trunk area of the car. A
second, hidden, storage area is located under the removable floor panel. .
||The hidden "lower trunk" is lined with
a polyethylene "tub". I cut an aluminum plate to exactly fit this tub and
mounted all the radio hardware on it. This plate, insulated from the
car's chassis by the plastic tub) also serves as a common point ground for
all equipment powered by the second battery (An Optima Spiracell Yellowtop
deep-cycle AGM). The objective was to avoid having the 20-30 amps of DC
current used by the ham gear from circulating on the car's chassis and
possibly interfering with the car's complex electronic control systems.
The car's own 12 volt battery system is located in the right-rear corner of
the trunk. As a result, I had a very short cable run to connect my
added battery system to the OEM battery via a Hellroaring Technology battery
isolator switch. The carpeted panel over the front edge of the opening
covers the 240 VDC hybrid battery.
The main chassis of the Yaesu FT100 is at the left side of the picture.
The Kenwood D700 chassis is located under the passenger seat. The
layout on the plate was planned with the possibility of accommodating the
main chassis of a Kenwood TS2000 in the future.
||Two antennas installed with no-holes
hard mounts. A Yaesu ATAS-100 mini-screwdriver for 40 through 6M is on the
left side. A Comet SB-14 6-2-450 antenna is mounted to the right. The
details of the home-brew brackets are shown in the next two pictures.
||These home-brew mounting brackets are
bent from .090 mild steel. Each one has a piece of rubber cut from an old
inner tube glued to it to avoid scratching the surface it is bolted to. The
horizontal surface of the "wing" is punched with a suitable hole (5/8"
for a SO-232 bulkhead connector for mounting the ATAS-100, or 3/4" for
installing an NMO mount for the VHF/UHF antenna).
to download a drawing with the dimensions of this bracket, in Acrobat .PDF
||The antenna mount bracket installed.
You remove the two bolts securing the hatch lifter rod bottom end, slip the
antenna mount between the hatch sidewall and the lifter, and re-insert the
bolts. (Prop up the hatch door with an old broom handle or stick
before unbolting the support.) There is just enough clearance between
the trunk lid and the sides of the hatch opening for the mounts to not
interfere with the movement of the trunk lid.