[aprssig] Prius

Stephen H. Smith wa8lmf2 at aol.com
Thu Apr 19 17:09:39 CDT 2007

bruninga at usna.edu wrote:
> There was some PRIUS discussion on the sig that I completely
> ignored.
> Last night my car blew up, and out of the blue, I am looking for
> a used car for my APRS addiction, and I was surprised to find
> PRIUS hybrids on the used market at comparable prices to other
> used cars.
> So what was the bottom line about PRIUS and APRS (and
> particualarly, I am interested in the PLUG-IN conversions...)?
> >From what I can tell, one would want a 2004 or later, since it
> has a CAN-BUS serial bus that you can tap into with your laptop
> and communiate with everything from the tailpipe to the engine.
> Bob, WB4APR
> _______________________________________________

1)   The Prius main power 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 which gets worse when you hit the brakes (which makes the motor 
run backwards as a generator.   The noise shows up even at VHF where it 
registers about S-1 or S-2 on the D700 S-meter.

2)   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 49-50A 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 220 VDC system which in turn is controlled by the 12 VDC powered 
computer systems.)

In my install in a 2006 Prius, I installed a second 50AH deep-cycle 
battery with an intelligent voltage-sensitive isolator to run the 
computer and ra dios 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.

3)   I have observed no interference problems TO the Prius' complex 
electronics at all, even with 100W on HF or 2M.

4)  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 A/C 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. Very handy when operating 
mobile-at-halt for some special event.   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. 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 gensets.]

I have plans for some nifty no-holes antenna mounts that I designed to 
install on the Prius if interested.

5)    A third-party adapter can adapt 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. 


Stephen H. Smith    wa8lmf (at) aol.com
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