How to test /trigger HV battery fan

It's two wires and fan will spin if you hook those up to 12volts, or even 6 volts. Alternatively you can use Hybrid assistant app via a $20 OBD2 code reader.

 

An easy way to test if the hybrid battery cooling fan is running is to use a tissue or piece of paper and place it on the intake vent. If the paper or tissue is sucked towards the intake, the fan is working.

FYI, the fan can run at 6 different speeds. It is very difficult to hear the fan running at speeds 1 to 3.

 

I can almost guarantee you the fan is running if the plug that's the issue has been dealt with . If driving car stop like getting gas leave car ready listening ears on vent Intake . You'll hear faintly a fan motor . If it's hot enough ya really hear it . . Can you make more flow and colder probably so . Will it do much for you ? Probably not a whole lot . All the new stuff today is now using Freon various gases coolant and so on to actually cool things not just air.. air worked well until it do not.

 

If there is an electrical fault with the battery fan then the ecu will set a fault code and turn on many warning lights - but only when the ecu tries to turn on the fan.
I know I can't hear the fan below 125° (speed 3), so I assume speed 1 should happen by 105-110?

Posted via the PriusChat mobile app.

 

Couple other points, fan is designed to increase with engine and vehicle speed so riding in the back seat next to intake might help. But you already bench tested it and you get warning lights if it doesn't work in the car so you don't need to worry. One additional step you'll want to take though is a low voltage to hybrid battery cooling fan error code is the most common problem and that's because there is a plug for that circuit slightly higher and further towards back of the car of the cooling fan. That plug gets wet and corrodes when roof seams fail and humidity in that part of the car stays high. Easiest fix is to eliminate that inappropriate plug and crimp those wires to each other directly.

 

The hybrid cooling fan speed is NOT dependent on engine RPM or vehicle speed. It is only dependent on the temperature of the hybrid battery.

 

I'm not sure; I seem to recall posts here indicating that it had been observed to ramp up and down with road speed, perhaps to sneak in a bit more cooling when road noise would cover the sound. I don't think I have saved links to those posts, though, so I'm not sure how long it'd take to find them again, assuming I'm not just imagining them.

 

Below are the results of some data logs that I once collected. I did not happen to notice any variation dependent upon vehicle speed. However, when watching fan speed on my monitor, I have noticed that sometimes the fan runs slower than expected from this table when the car has been standing in the sun and the cabin is very hot. Presumably, to avoid sucking in air that is even hotter than the battery. The following table is based on data collected while the cabin was below about 25° C:

HV Battery Fan Speed Transition Temperatures
Extrapolated from OBD logger data
2007 Toyota Prius

Fan
Speed - Temperature
----------------------------
0 to 1 @ 36° C
1 to 0 @ 34° C

1 to 2 @ 39° C
2 to 1 @ 37° C

2 to 3 @ 42 °C
3 to 2 @ 40 °C

3 to 4 @ 50° C
4 to 3 @ 48° C

4 to 5 @ 52° C (and reduced battery current limit)
5 to 4 @ 50° C

5 to 6 @ 56° C
6 to 5 @ 54° C