General Disclaimer:   (HV) (DC) injury or death hazard,   use at your own risk,   may void warranty.

Difference between pages "PriusPlus-Theory" and "Prius OEM fan control"

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==Theory Overview==
 
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'''Todo''' This needs to be polished, but its just a quick overview for someone looking to do a conversion of how the system functions.
 
  
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The fundamental basis of this conversion is the reported state of charge (SOC) of the stock NiMH battery in the Prius and keeping that reported state of charge where we want it to encourage the hybrid synergy drive (HSD) to use as much electric power as possible (at the right times) to offset gasoline usage.  During different driving profiles, it is better to use electricity at different times.  However, putting that aside for now, generally, to allow all EV driving, the SOC needs to be kept in a certain range (typically around 60-63%).  When the reported SOC drops below the lower threshold, the PHEV battery and the OEM battery need to be paralleled.  It has been found that EV mode can cause the OEM battery voltage to drop below 200 volts while accelerating.  The algorithm for determining when to parallel the OEM battery and the PHEV battery needs to parallel the batteries when the voltage drops below 200 volts to make sure the car doesn't cancel EV mode because the OEM battery voltage is too low.  To get the Prius to use electricity in highway driving, the reported SOC needs to be brought up to over 70% (typically 72-73%, however, never exceeding 80%.) The charge current limit (CCL or ACL in CAN-View) must be monitored to make sure the OEM battery is not being overcharged or overheated. The Prius will then enter a "get rid of charge any way possible" and be encouraged to use more electricity (up to about 6kW.)  When the batteries are paralleled, it causes a voltage rise (because the PHEV pack is a higher nominal voltage than the stock battery). When the voltage hits a certain point, it causes a state of charge drift, which, once started, very rapidly increases the reported SOC.
+
Cooling for the [[Toyota Prius]] is done with simple air flow from a squirrel cage type fan capable of drawing about 6 amps for ample air flow.  Though the Prius almost never runs the fan at full speed.  In fact the fan isn't even powered until the battery temperature reaches ''?96°F'' and doesn't attempt to cool aggressively by speeding up the fan until the temperature is well above ''?120°F''.  This is perfectly acceptable for normal operation but for certain methods used to convert the car into a [[Prius PHEV]] more cooling is desirable.  There are a number of reasons such as:
 +
* The [[Prius EV Mode]] is not allowed if the battery is above 107°F.
 +
* The [[Battery Pack Configurations#Hybrid|Hybrid Battery Pack Configuration]] tends to warm the OEM battery during heavy use due to the charge current which is applied.
 +
* High temperatures limit the Charge Current Limit leading to something similar to the [[State Of Charge Manipulation#Charge Limit Conundrum|CCL Conundrum]].
  
−
In the current revision of the system, CAN-View (a computer sitting on the CAN bus monitoring status) is responsible for controlling the contactors.  See below for more information on specific relays on CAN-View. The output from the 6 CAN-View relays is fed into a logic statement (currently just relay 3 OR 5 OR 6) to determine when to parallel the two packs. Another relay (#4) is a special relay turned on when the system is enabled, and off when the system is disabled.
+
So for these reasons such conversions have devised methods for overriding the OEM Fan control so that the fan can be run faster in order to keep the battery at a lower target temperature.  This may also be handy for stock cars in hot climates and can be easily implemented as a stand alone modification without the full PHEV conversion.  Here is how OEM battery fan control is dealt with for a pair of PHEV conversions:
 +
* [[PriusPlus-Theory#OEM Battery Fan Controls]]
 +
** [[PriusPlus-Instructions#OEM Battery Fan Control Tap]]
 +
** [http://autos.groups.yahoo.com/group/eaa-phev/message/688 Y!:Prius OEM battery fan control info]
 +
* A portion of the [[PiPrius conversion process#Interlock Box]] schematics [[:Image:Interlockschematic.png]] handles OEM fan control for the [[PiPrius]] project.
  
−
==The PHEV Battery Pack==
+
As an alternative to cutting Prius wires you can purchase the following OEM battery plug and mating pins, though they are not inexpensive:
 +
* OEM battery fan plug pins:  Toyota P/N 82998-12380
 +
* OEM battery fan plug mating pins:  Toyota P/N 82998-12370
  
−
The PHEV pack consists of twenty 12 volt 20 amp hour sealed lead acid batteries connected in series.  The batteries themselves sit in an aluminum box and are mounted above the spare tire well, but below the false floor in the trunk.  The pack has a nominal voltage of 240 volts and has a total energy storage of about 4.8 kWh (not all usable.)  In this design, the PHEV battery pack has a higher nominal voltage than the stock NiMH battery and is used to charge the stock NiMH battery.  Contactors (large relays) are used to connect and disconnect the PHEV battery pack from the stock battery when charging is needed.  The higher voltage pack cannot always be connected to the stock pack, because that would overcharge the batteries.  NiMH battery packs also cannot easily be charged in parallel, so simply adding a second NiMH battery pack is not simple.  The current from the battery pack is less than 60 amps, and therefore the pack is fused with 60 amp 300VDC (or higher) fuses.  The batteries must be connected using 8 AWG wire or larger (smaller AWG number) to handle the amount of current.
+
== Stand along OEM fan control ==
 +
Using the same method employed by the PiPrius conversions you can build a simple stand alone circuit capable of overriding the OEM fan control and running the fan at full speed instead which rapidly removes heat from the OEM battery pack.
  
−
The PHEV battery does not have its own battery management computer. As the PHEV battery’s state-of-charge (SOC) decreases, it is put in parallel with the OEM battery more and more continuously.  Charge-sustaining operation at the PHEV battery’s minimum intended SOC occurs when the PHEV battery’s voltage matches the voltage of the OEM battery’s 60% SOC voltage well enough that average PHEV battery current becomes zero.  This is a soft limit that depends upon driving conditions, temperatures, PHEV battery condition, and the state of the moon; and PHEV operation slowly morphs into hybrid operation rather than changing abruptly.  Ordinarily, around 10-13 Amp-hr is removed from the PHEV battery before electric assist is exhausted.  The depth-of-discharge (DOD = 100% - SOC) that this corresponds to is anyone’s guess, as due to Peukert’s Law (PbA batteries have lower capacity at high discharge rates) and high, variable discharge rates, the battery pack’s capacity is diminished by a large, unknown amount.
+
=== Parts List ===
 +
[[Image:DSC00378.JPG|thumb|right|The parts, note that a smaller capacitor was used.]]
 +
* Shielded blade type crimp connectors (light blue)
 +
* 16 awg Wire (Green, Violet, Red, Black, and White)
 +
* Heavy fence wire, or a metal coat hanger
 +
* Eyelet crimp connector (Red, large eyelet)
 +
* A DPDT Relay and matching socket (10A contacts)
 +
* Two (2x) 220ohms 1/4 watt resistors
 +
* A 330uF Alum capacitor (error toward higher values)
 +
* 7.5A fues and fuse holder
 +
* Hot glue gun with high temp glue
  
−
===Current PbA limitations===
+
=== Construction ===
−
*The conversion adds 300+ lbs to the vehicle’s weight to provide 10 miles of electric range per charge (16.7 usable Wh/kg)
+
{{Disclaimer}}{{Clear}}
−
**Though Ron has safely driven 17,000 miles in his converted Prius, the added weight could possibly cause vehicle instability during driving, and the battery may modify the effectiveness of the vehicle’s rear crush zone.
+
[[Image:DSC00372.JPG|thumb|right|Splicing OEM fan circuit wire near fan connector.]]
−
**Existing conversions sit 1-2 inches low in the rear. Air shocks or heaver-duty rear springs would be nice, but have not yet been developed.
+
[[Image:DSC00381.JPG|thumb|right|The heavy wire used for mounting.]]
−
**Though there are indications that improved hybrid efficiency due to a lower combined internal resistance of the two-battery combination at least partially compensates for the added weight, city gasoline mileage is otherwise reduced by up to 10%.
+
[[Image:DSC00426.JPG|thumb|right|Fully wired, just need to insulate.]]
−
*Operating costs are high due to an expected cycle life of only 300-400 deep cycles, providing only one to two years of daily driving (at 400 cycles, 10 electric miles per 2.1 kWh cycle, and $800/pack, battery cost is $0.95/kWh throughput or $0.20/electric-mile (in addition to the cost of electricity, usually 2-4 cents/mile depending on utility rates).
+
[[Image:DSC00434.JPG|thumb|right|Used hot glue to insulate.]]
−
*For decent battery life, the battery must always be charged within a day of discharge, making charging a required rather than optional operation (if planning to drive to somewhere without access to electricity, temporarily turn off PHEV operation).
+
[[Image:DSC00387.JPG|thumb|right|Mounted in car near OEM fan.]]
−
*PbA batteries perform very poorly in cold weather.  Though our design includes a thermally insulated battery pack, heated during charging, this feature has been insufficiently tested due to moderate California temperatures during development.
+
# You will need to cut the OEM can wires between the support clip and the plug which attaches to the fan.
 +
#* There are two green and two violet wires, attach insulated blade crimp connectors to the OEM wires in such a manner that they can be plugged back into their original configuration.  Use the same gender on the wires leading to the fan, and the other gender on the other wires which lead to the OEM CPU.
 +
# The Heavy eyelet is used as a ground point and for structural support when mounting the circuit.
 +
#* Use heavy fence wire, or a pliable metal coat hanger (not so heavy that it's difficult to bend).  Wrap the wire around the relay socket twice leaving an two inches or so of excess twisting out from one side.  You will attach the ground wire and the large eyelet crimp connector to the end of the heavy wire for mounting it to a ground point.
 +
#* Use hot glue to ensure that the wire wrapped around the relay socket can't work it's way off due to vibration.
 +
#* You may also choose to solder the eyelet to the ground wire and heavy wire after crimping.
 +
# Solder the short black ground wire to one of the coil pins of the relay socket and also (or another length) to the NO (Normally Open) pin of one of the relays throws.
 +
# Solder a 12" length of Violet wire to the swinger pin on the same throw.  To the other end crimp a blade connector which will mate with the connector leading to the fans Violet wire.
 +
# Solder a long length of White wire to the remaining coil pin on the relay socket, this will be energized with +12v to enable the fan control override so you may want it to reach the drivers seat area.
 +
# Solder a 24" length of Red wire which must also be fused to the unused NO pin of the other throw.  This wire will be attached to the +12v accessory battery to power the OEM battery fan.
 +
# Solder a 12" length of Green wire to the unused swinger pin.  To the other end crimp a blade connector which will mate with connector leading to the fans Green wire.
 +
# To the remaining two NC (Normally Closed) pins you will need to attach the two 220 ohm 1/4 watt resistors and the 330 uF Alum (Polarized) capacitor, these will fool the Prius CPU into thinking that there is still a fan attached when we disconnect the real fan from it.
 +
## Solder a 12" length of Green wire and one leg of one of the resistors to the Green NC pin (The throw with the Green and Red wires already attached). To the other end of the wire crimp a blade connector which will mate with connector leading to the CPUs Green wire.
 +
## Solder a 12" length of Violet wire, one leg of the other resistor, and the negetive(-) leg of the capacitor to the Violet NC pin (The throw with the Violet and ground wires already attached.  To the other end of the wire crimp a blade connector which will mate with connector leading to the CPUs Violet wire.
 +
## Solder the remaining three legs, two resistor legs and positive(+) capacitor leg together, they should not touch any other points.
 +
## Use an insulating material such as hot glue to insure that none of the pins nor components soldered to the relay socket can be touched.  We don't want anything to get grounded once it's installed.
 +
# Install by securing the eyelet under the nut which holds a metal bracket with a wire disconnect attached just above the OEM cooling fan.  Plug the Green and Violet wires into their proper locations between the CPU and Fan at the splice location.  Attach the fused +12v wire to the accessory battery positive(+) post.
 +
# Now any time that the White wire is supplied with +12v the OEM fan should roar to life at full power.  You can now program your [[CAN-View]] to turn on the fan at above some temperature such as 95°F.  Or you can simply attach the wire to a toggle switch that you can turn on and off, but be sure that the switch is attached to an acc/run +12v source such that if you leave the switch on when the car is off it won't continue to run and drain your accessory battery.
  
−
===Possible Future Battery Options===
+
=== Photos Schematics ===
−
More advanced batteries may be retrofittable to the conversion.  This will probably require upgrading to CalCars’ not-yet-designed next version of logic board, and will also probably require additional battery management electronics. Any new battery’s enclosure, mounting, and thermal management system will no doubt also be very different.
+
[[Image:DSC00433.JPG|thumb|right|The circuit.]]
 +
*      ___                                            *
 +
      / _ \
 +
      ( (_) )
 +
  Ground\___/wire to eyelet
 +
    ___|X
 +
    |  X  ___________________________Fan {Violet}
 +
    |___X__|______    __________________CPU {Violet}
 +
----|---X--|-----|-----|-----
 +
|  |      |    |    |    |
 +
|  O      O    O    O____|__________
 +
|                          |      |  |-
 +
|  coil  swing  NO    NC  |    R2  C1
 +
|                      ____|__R1__|__|+
 +
|  O      O    O    O    |
 +
|  |      |    |    |    |
 +
----|------|-----|-----|-----
 +
    |      |    |    |_________________CPU {Green}
 +
    |      |_____|____________________Fan {Green}
 +
    |            |
 +
    |        +12v fused {Red}
 +
+12 to enable {White}
 +
  *'''Relay Socket Wiring'''                                  *
  
−
Possible future batteries and their likely characteristics (incl. low-volume pricing):
+
[[Category:PHEV]]
−
 
+
[[Category:Prius]]
−
Example pack
+
[[Category:PiPrius]]
−
{| border=1 cellpadding=2 |
+
[[Category:PriusPlus]]
−
| Chemistry || || Usable<br>Wh/kg || Cycle<br>life || Yr daily<br>driving || $/usable<br>kWh || $/kWh<br>thruput || Cents/<br>EV-mi || kWh || $ || EV mi || Wt,<br>lb
 
−
|-
 
−
| PbA<br>(current) || || 16 || 400 || 1.1 || $380  || $0.95  || 20.0  || 2.1 || $    798 || 10 || 289
 
−
|-
 
−
| NiMH || worst || 36 || 2000 || 5.5 || $1,200 || $0.60 || 12.6 || 4.2 || $5,040 || 20 || 257
 
−
|-
 
−
| NiMH || best || 36 || 4000 || 11.0 || $800 || $0.20 || 4.2 || 4.2 || $3,360 || 20 || 257
 
−
|-
 
−
| Li-ion || worst || 56 || 1000 || 2.7 || $1,200 || $1.20 || 25.2 || 4.2 || $5,040 || 20 || 165
 
−
|-
 
−
| Li-ion || best || 100 || 4000 || 11.0 || $800 || $0.20 || 4.2 || 6.3 || $5,040 || 30 || 139
 
−
|-
 
−
| NiZn || worst || 36 || 500 || 1.4 || $500 || $1.00 || 21.0 || 4.2 || $2,100 || 20 || 257
 
−
|-
 
−
| NiZn || best || 36 || 2000 || 5.5 || $350 || $0.18 || 3.7 || 4.2 || $1,470 || 20 || 257
 
−
|-
 
−
| Firefly PbA || worst || 36 || 1000 || 2.7 || $350 || $0.35 || 7.4 || 4.2 || $1,470 || 20 || 257
 
−
|-
 
−
| Firefly PbA || best || 45 || 4000 || 11.0 || $250 || $0.06 || 1.3 || 5.25 || $1,313 || 25 || 257
 
−
|}
 
−
 
 
−
Note that figures are for usable, not total, capacity in kWh (usually 80%, but much less for the current PbA pack (4.8 kWh total capacity), due to Peukert’s Law).
 
−
 
 
−
==The Charger==
 
−
 
 
−
The charger runs on standard 120v (or 240v) AC power and is used to recharge the PHEV pack.  Three options are planned:
 
−
*a Delta-q charger (http://www.delta-q.com) designed for the PbA battery pack, at a projected price of $800.  We are in discussions with the company and will soon know if/when pre-production units will be available; UL-approved units are likely to be available in 2007.
 
−
*the Brusa NLG503 charger, available through http://www.metricmind.com/index1.htm for $2650 retail including cables (a group rate is possible).  Users can reprogram this charger for other voltages and battery chemistries, so it would be a good purchase for developers anticipating an eventual high-tech replacement battery.
 
−
*(eventually) the Manzanita Micro PFC-40 charger, available through http://manzanitamicro.com for around $2000.  This charger has programmable but less sophisticated charging algorithms, but can also double as a high-power DC:DC converter between the battery packs.  Its output is ''not'' line isolated.  Its incorporation will require modifications/enhancements of this conversion, and control circuitry and algorithms that have not yet been developed.
 
−
 
 
−
Useful information on charging lead-acid batteries can be found at [http://batteryuniversity.com/partone-13.htm http://batteryuniversity.com/partone-13.htm]
 
−
 
 
−
==The CAN-View==
 
−
 
 
−
The [[CAN-View]] is a computer which monitors the [[CAN]] bus (the bus which the different microprocessors in the Prius use to communicate with each other) and both displays information to the driver on a display as well as control the extra plug-in systems.  The Can-View computer can be programmed to turn on and off a series of relays which are used to control the PHEV operations.  There are currently 2 versions of CAN-View available.  Version 3 requires an '04 or '05 Prius and makes use of the built in display (or [[MFD]]) while Version 4 works with an 04-07 Prius but requires an external touchscreen (since the built in touchscreens were changed in the '06 model and are no longer compatible.)  CAN-View is simple to install and installation typically requires between a half hour to one and a half hours.  For more information, see [[CAN-View]].
 
−
 
 
−
Version 3 of [[CAN-View]] must be ordered with the PHEV relay board option to be used in this conversion.  Version 4 comes standard with the PHEV relays.  [[CAN-View]] has 6 relays.  Relays RL1 and RL4 are special relays which are try-EV mode and PHEV/orig.  RL4 is triggered by pressing "orig/PHEV" on the CAN-View screen.
 
−
 
 
−
RL2, RL3, RL5 and RL6 are programmable.
 
−
 
 
−
==EV Mode Button/Wire==
 
−
The Prius can be put into "EV" mode which essentially turns the car into an electric car for speeds under 34mph.  While Prius's come standard with a button in the dash in some countries, the button is not on the North American model, however the software is still present.  EV mode can be entered by momentarily grounding pin 27 on plug H16 on the HV ECU.  If the car exceeds 34mph or a host of other conditions are not met (such as the current charge limit, OEM battery temperature, low SOC, throttle, etc), the Prius will automatically exit EV mode and resume ICE use.  For more detailed information on EV mode, see [[Prius EV Mode Button]].
 
−
 
 
−
==Control Circuit Board==
 
−
 
 
−
A circuit board is needed which contains the logic to control the added heaters, fans, contactors, etc.  The board is roughly 5" by 6" and is mounted in the electronics tray, between the PHEV battery and the stock battery.
 
−
 
 
−
Sub parts of this board are;
 
−
* Power management - takes input from CAN-View and controls the contactors connecting the PHEV battery with the stock battery.
 
−
* Battery Heating & Cooling - senses and controls the fans and heaters to keep battery temperatures within defined ranges.
 
−
* System diagnostics - A simple LED board interface to monitor the technical operation of the system for debugging.
 
−
* Charge interlock - stops the car from being driven away while plugged into a live outlet.
 
−
 
 
−
===PHEV Battery Heating & Cooling===
 
−
 
 
−
Lead acid batteries do not function as well when they are either hot or cold.  The pack is heated and cooled as necessary by three standard 12" x 15" heating pads and three fans.  The circuit board is responsible for controlling the heaters and fans.  Depending on the layout, vents are provided either throught he bottom of the tire well or through the stock vent behind the storage bin on the rear drivers side of the car.
 
−
 
 
−
===OEM Battery Fan Controls===
 
−
The OEM controller connects the light green wire to the OEM fan to +14V when the OEM battery temperature reaches around 89-96 deg F.  This control leaves that connection in place but taps it and runs it to J8F pin 1.  Once the fan is so energized, proportional control is affected by varying the current to the violet line to the negative terminal of the OEM fan.  The voltage of this line is monitored, and a DTC (system error) is asserted if the fan has become an open circuit.  Control is effected by removing the violet line from the OEM fan and running it instead to J8F pin 3.  J8F pin 5 is then run to the OEM fan.  A diode (actually 3 in-line 3A diodes in parallel to handle 5A) between pin 3 and pin 5 allows the OEM control to operate the fan normally when the control board is unplugged (J8F plugs into J8M on the control board).
 
−
 
 
−
The control board has a 2.2K resistor between pins 1 and 3 of J8, a controlled pullup from pin 1 to +14V, and a controlled pulldown from pin 5 to chassis ground.  When not in PHEV mode, the control board does nothing.  When in PHEV mode, pin 5 is always pulled down to ground.  This causes the fan to run at full bore whenever there is power on pin 1 (normally when the OEM battery temperature is above 89-96 deg F).  The 2.2K resistor provides just enough load to the OEM proportional control circuit that it doesn't think the fan is an open-circuit and declare a DTC (hybrid system error).  At the cost of some passenger compartment noise, this keeps the OEM battery temperature below 100 deg F instead of around 114 deg F, thereby keeping it cool enough for EV mode, which will not work when the OEM battery's temperature is above 104 deg F, to continue to be enabled.  It would no doubt be possible to proportionately control the fan to this lower temperature, too, but this system is not yet that sophisticated.
 
−
 
 
−
The pullup on J8 pin 1 is to allow the PHEV system to force the OEM fan ON when desired and the OEM battery temperature is below 89-96 deg F.  A recommended use of this feature is to force the fan ON when the OEM battery temperature is so low that discharge current limit (DCL) is below 100A, thereby (sometimes severely) limiting EV mode current.  If the driver, as would be expected, is using the cabin heater, the fan can speed up the heating of the OEM battery by blowing cabin air over it, thereby enabling EV mode sooner than without forcing the fan ON.
 
−
 
 
−
==Electronics Tray==
 
−
 
 
−
===HVD1===
 
−
The purpose of the diode is to allow energy from the regen braking into the PHEV battery pack.  This functionality is off when CAN-View's ORIG/PHEV relay is set for ORIG (which turns off HVRL2.)  The heatsink can dissipate >200 watts for short braking or around 100 watts for several minutes during downhill braking, and must be well connected to the heatsink and in the path of a fan when is on whenever the car is in ready mode.  The diode will only heat when braking or when the battery is being charged by the ICE.  The diode requires a DO-5 mounting kit to insulate the diode from the heatsink electrically, but still allow thermal conductivity.
 
−
 
 
−
===Contactors===
 
−
HVRL1 is responsible for paralleling the PHEV battery pack and the OEM Prius battery.  HVRL2 is responsible for enabling / disabling the system.  HVRL3 is used for the optional power resistor.  HVRL1 and HVRL2 both have snubbers across the terminals to reduce arcing and extend the life of the contactors.
 
−
 
 
−
==References==
 
−
<references/>
 

Revision as of 09:27, 9 October 2007

Cooling for the Toyota Prius is done with simple air flow from a squirrel cage type fan capable of drawing about 6 amps for ample air flow. Though the Prius almost never runs the fan at full speed. In fact the fan isn't even powered until the battery temperature reaches ?96°F and doesn't attempt to cool aggressively by speeding up the fan until the temperature is well above ?120°F. This is perfectly acceptable for normal operation but for certain methods used to convert the car into a Prius PHEV more cooling is desirable. There are a number of reasons such as:

So for these reasons such conversions have devised methods for overriding the OEM Fan control so that the fan can be run faster in order to keep the battery at a lower target temperature. This may also be handy for stock cars in hot climates and can be easily implemented as a stand alone modification without the full PHEV conversion. Here is how OEM battery fan control is dealt with for a pair of PHEV conversions:

As an alternative to cutting Prius wires you can purchase the following OEM battery plug and mating pins, though they are not inexpensive:

  • OEM battery fan plug pins: Toyota P/N 82998-12380
  • OEM battery fan plug mating pins: Toyota P/N 82998-12370

Stand along OEM fan control

Using the same method employed by the PiPrius conversions you can build a simple stand alone circuit capable of overriding the OEM fan control and running the fan at full speed instead which rapidly removes heat from the OEM battery pack.

Parts List

The parts, note that a smaller capacitor was used.
  • Shielded blade type crimp connectors (light blue)
  • 16 awg Wire (Green, Violet, Red, Black, and White)
  • Heavy fence wire, or a metal coat hanger
  • Eyelet crimp connector (Red, large eyelet)
  • A DPDT Relay and matching socket (10A contacts)
  • Two (2x) 220ohms 1/4 watt resistors
  • A 330uF Alum capacitor (error toward higher values)
  • 7.5A fues and fuse holder
  • Hot glue gun with high temp glue

Construction

General Disclaimer:   (HV) (DC) injury or death hazard,   use at your own risk,   may void warranty.

HV (High Voltage) DC (Direct Current) Warning: Traction Battery Packs, Motors, Chargers, and other HV sources could cause serious injury or death if proper precautions are not taken while working on or around such High Voltage Direct Current sources.

Use this information at your own risk: There is no warranty expressed nor implied and we are not liable for any of your past, present, nor future actions. Even should you perform these modifications to the letter you could still damage any number of components in your vehicle causing it to no longer function. Even if it appears to function properly your actions may cause it to self destruct with collateral damage to surrounding properties other than your vehicle. By utilizing these ideas and instructions in an attempting to enhance national security, reduce gas consumption, vehicle "emissions", your carbon footprint, or smog, you do so at your own risk & peril.

Warranty: In performing some of these modifications you may void your warranty with the vehicles manufacturer.

See also our My wiki:General disclaimer

Splicing OEM fan circuit wire near fan connector.
The heavy wire used for mounting.
Fully wired, just need to insulate.
Used hot glue to insulate.
Mounted in car near OEM fan.
  1. You will need to cut the OEM can wires between the support clip and the plug which attaches to the fan.
    • There are two green and two violet wires, attach insulated blade crimp connectors to the OEM wires in such a manner that they can be plugged back into their original configuration. Use the same gender on the wires leading to the fan, and the other gender on the other wires which lead to the OEM CPU.
  2. The Heavy eyelet is used as a ground point and for structural support when mounting the circuit.
    • Use heavy fence wire, or a pliable metal coat hanger (not so heavy that it's difficult to bend). Wrap the wire around the relay socket twice leaving an two inches or so of excess twisting out from one side. You will attach the ground wire and the large eyelet crimp connector to the end of the heavy wire for mounting it to a ground point.
    • Use hot glue to ensure that the wire wrapped around the relay socket can't work it's way off due to vibration.
    • You may also choose to solder the eyelet to the ground wire and heavy wire after crimping.
  3. Solder the short black ground wire to one of the coil pins of the relay socket and also (or another length) to the NO (Normally Open) pin of one of the relays throws.
  4. Solder a 12" length of Violet wire to the swinger pin on the same throw. To the other end crimp a blade connector which will mate with the connector leading to the fans Violet wire.
  5. Solder a long length of White wire to the remaining coil pin on the relay socket, this will be energized with +12v to enable the fan control override so you may want it to reach the drivers seat area.
  6. Solder a 24" length of Red wire which must also be fused to the unused NO pin of the other throw. This wire will be attached to the +12v accessory battery to power the OEM battery fan.
  7. Solder a 12" length of Green wire to the unused swinger pin. To the other end crimp a blade connector which will mate with connector leading to the fans Green wire.
  8. To the remaining two NC (Normally Closed) pins you will need to attach the two 220 ohm 1/4 watt resistors and the 330 uF Alum (Polarized) capacitor, these will fool the Prius CPU into thinking that there is still a fan attached when we disconnect the real fan from it.
    1. Solder a 12" length of Green wire and one leg of one of the resistors to the Green NC pin (The throw with the Green and Red wires already attached). To the other end of the wire crimp a blade connector which will mate with connector leading to the CPUs Green wire.
    2. Solder a 12" length of Violet wire, one leg of the other resistor, and the negetive(-) leg of the capacitor to the Violet NC pin (The throw with the Violet and ground wires already attached. To the other end of the wire crimp a blade connector which will mate with connector leading to the CPUs Violet wire.
    3. Solder the remaining three legs, two resistor legs and positive(+) capacitor leg together, they should not touch any other points.
    4. Use an insulating material such as hot glue to insure that none of the pins nor components soldered to the relay socket can be touched. We don't want anything to get grounded once it's installed.
  9. Install by securing the eyelet under the nut which holds a metal bracket with a wire disconnect attached just above the OEM cooling fan. Plug the Green and Violet wires into their proper locations between the CPU and Fan at the splice location. Attach the fused +12v wire to the accessory battery positive(+) post.
  10. Now any time that the White wire is supplied with +12v the OEM fan should roar to life at full power. You can now program your CAN-View to turn on the fan at above some temperature such as 95°F. Or you can simply attach the wire to a toggle switch that you can turn on and off, but be sure that the switch is attached to an acc/run +12v source such that if you leave the switch on when the car is off it won't continue to run and drain your accessory battery.

Photos Schematics

The circuit.
*      ___                                            *
      / _ \
     ( (_) )
Ground\___/wire to eyelet
    ___|X
    |   X  ___________________________Fan {Violet}
    |___X__|______     __________________CPU {Violet}
----|---X--|-----|-----|-----
|   |      |     |     |    |
|   O      O     O     O____|__________
|                           |      |  |-
|  coil  swing   NO    NC   |     R2  C1
|                       ____|__R1__|__|+
|   O      O     O     O    |
|   |      |     |     |    |
----|------|-----|-----|-----
    |      |     |     |_________________CPU {Green}
    |      |_____|____________________Fan {Green}
    |            | 
    |        +12v fused {Red}
+12 to enable {White}
*Relay Socket Wiring                                  *
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