High Voltage Battery Blower Modification - "Plug and Play" module

I received my scangauge II a few weeks ago because I had a fault light that needed to be diagnosed. I was always curious about the temperature of the high voltage battery and the temps are higher than what I anticipated. Even after the Prius is parked, not only will the temperature rise in certain situations, it takes forever to cool down. Even after sitting overnight, the battery temperature can still be high.

This led me to install the battery blower modification and it works great. Wiring up the relay isn't hard but it was tedious and I was looking for a cleaner installation. I have a production run of 200 PCB's that were never used (never enter into a verbal contract) so I reworked it to install the battery blower modification. The PCB I'm using incorporates a microcontroller so I decided to also use a timer after the Prius is powered down. This allows the battery to continue to cool after I've left the car.

The only thing the user would need to do is supply power to the board (-12 and +12), run one wire to turn the blower on and cut the green and purple wires. For lazy people or people who like gadgets, the board has a wireless IC as well so you don't even have to run a wire to the front of the car and you can use a remote control to turn it on and off. I can program the board however you would like if there's something special you want.

Not looking for much, just looking to recoup the cost of the parts and the board. The board size is 4.125" W by 2.575 L. It has screw down terminal blocks on the board and makes the installation easier. I'll throw a one year warranty on the board.

 

Yes, the OEM fan is used.

You can install the PCB anywhere you want but I put it close to the fan so the wires are shorter. I've thought about using an additional battery and using a diode (or relay) to isolate the power supply for the fan when the car is off. I haven't tested how much the current consumption from the fan (4.2 amps I think) affects the longevity of the battery or the day-to-day use. I don't think that leaving the fan on for five minutes or so would be a huge issue but I'm sure many people on here have done extensive testing on the battery and could provide some helpful comments.

When I get home tonight I'll take some pics and post them.

 

Here is a pic of the board. The connections that needed to be made to the board are:

Green OEM fan
Violet OEM fan
Green CPU
Violet CPU
+12 VDC
-12 VDC
Momentary button wire

Installation is a piece of cake. The hardest part will be running the momentary button wire to the front, which is relatively easy. I've found that when using the fan as the battery temperature approaches 95 degrees, it doesn't go higher and the temps I've seen in the 120's doesn't happen anymore.

I also have an output on the board that controls an LED. I use this as a feedback to tell me if the fan is on or off and if the timer is activated.

The program looks like this (fan is starting in the off position):

Button pressed and released in less than two seconds
Fan is turned on (15 minute max in the event you forgot to shut it off)
LED is steady on

Button pressed and released in less than two seconds
Fan is turned off and reverts to OEM control (forever)
LED is off

Button pressed and held for for more than two seconds
Fan turns on and runs for X minutes
Led blinks at one second intervals

 

Speaking from memory here but these numbers are close. Anything below 85 degrees Fahrenheit and anything above 105 degrees Fahrenheit will result is reduced regen. I live in a hilly area and getting the pack to 105 on a 80 degree day isn't difficult to do at all.

 

Yes, I was trying that out last weekend. To do it with hardware isn't that difficult but to do it with software may be tricky. That was one of the things I was going to look into next weekend.

I've seen my CCL down very low as well. The other thing to consider when the traction battery gets warm is:

1. Heat reduces the life of a battery.

2. When the heat is increased in the battery, you recoup less energy and that's a waste!

3. I didn't realize the answer to this thought until I received my scangauge. Sometimes I "felt" like my car wasn't stopping as good as it should. I thought it was all in my head. Then when I received my scangauge I was able to see that my Prius was just letting the energy turn into heat by way of the brake pads! Not only does the comment in point #2 come into play but you're also shortening the life of the brake pads, rotors and drums as well. Granted, it's not significant but it's still money wasted.

 

Checking the fan for obstructions/debris and if the fan was working properly is the first thing I did. I know you keep thinking the problem is everything else except the design of the fan or software to control it but I can tell you from experience that in my car it is the root cause of the heat buildup.

My proof is the fact that I can run at a steady speed on the highway (windows open or closed with A/C on) and my battery temp rarely gets above 95. When it's hot and I'm going up and down hills or stop and go traffic the battery temp rises without fail, sometimes into the 120's. Since I've installed the modification, I haven't seen a temp over 98.6 degrees.

 

Thanks for the information. Did you use a potentiometer or something like that to vary the voltage? I haven't had that much time to play with it but when I get some free time this weekend I will definitely see if I can make it work in a variable speed mode.

 

Ah, I see. From what I understand, you can only monitor these signals on a Gen II, whereas you can control and monitor on a Gen III.