Mobile Installation In 2005 Toyota Prius

 Photos of the installation are below.

• 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 systems.)
  
  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:
        http://hellroaring.com .  
  
  The isolator and second battery hookup is similar to the one shown on this page:
        http://hellroaring.com/Basic%20Aux%20Audio.php
   
• 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.)