GenII HV Battery Fan cleaning and testing

I was considering running the quick-connect out through the grill, but then had a thought: it's a long shot, but could someone connect the two pins of the quick connect with a jumper wire, short out the battery?

 

You would blow out the battery fuse first. Perhaps the 100amp in the box too?

 

Maybe even heavy rain could be a problem? Probably not, Christmas light extension cords never seem to mind, but who knows.

 

I'm currently doing maintenance of HV battery cooling system. Here are my observations and thoughts:
- P2 battery blower uses a DC brushed motor. It's normal, that such motors doesn't spin freely as there is a good amount of friction between brushes and commutator. Recently I got two DC motors from salvaged plotters and they spin freely only with brushes removed.
- My blower draws about 1A@3,7V and 5A@12V. It starts moving at about 1.1V and keeps spinning at 1.2 V drawing about 0.7A (The current varies from 0.55 to 0.8A as rotational speed at such low voltage is not stable, so is a back EMF). The currents measured at 3.7 and 12V are very similar to these mentioned in this thread: Cleaned hv blower and battery. Battery temp now hotter | PriusChat
- The service manual does not mention how much current the fan draws (amazingly it tells the current of cooler fans...). It only mentions that the resistance must be no more than 9 Ohms (mine is about 1 Ohm, which I assume is OK for the 12V/60W motor with healthy brushes).

- in order to dissipate a certain amount of heat through a cooling system which has a specific thermal resistance we need a certain temperature difference. For example to dissipate 10W from a transistor through a radiator with thermal resistance of 1°C/W the temperature diference between transistor and ambient air will be 10°C regardless of actual ambient temperature - the transistor will be always 10°C hotter than air. If we use a fan to push air through a radiator - the thermal resistance will decrease and the transistor will be cooler despite the same ambient tempreature and dissipated power.
Back to my prius - with fan operating at maximum speed the difference between inhaled air and battery is no more than 10°C(18F). At low speed it's at least twice as much. The problem is that charging current limit kicks in at 38°C(100.4F), but prius sets max fan speed loo late, so in hot days it's easy to overheat the battery and loose efficiency of regenerative braking. That's why I use HA to set level 6 of fan cooling at lowet possible temp (35°C/95F) and use AC to keep cabin below 28°C/82F.
Today I cleaned the fan blades (about 20% of space between blades was clogged with very fine dust) - will see next days if it improved cooling efficiency.

 

Thanks, Luc, very informative post. Look forward to your update.

 

I think there is a PID for the HV Battery Fan speed level, it will return a value of 0, 1, 2, 3.. etc. highest ive seen is 3, but i dont remember ever hearing it come on.. Here are some data i collected from Torque app, showing Fan Speed (green line at bottom) vs battery temperatures, (click to see full charts)

 

Maybe you might want to locate the information "you read somewhere" and share it with the forum.

That information just cannot be correct, as at level 3 you would not be really able to hear the fan, except if maybe you stuck your ear right up to the intake vent. We have had plenty of reports of the cooling fan running at level 6, such that it can be heard over road noise from the driver's seat while the car is travelling at speed.

I have used the active test in Techstream and commanded the fan to all speeds and it responded accordingly, so unless there is a defect in the ECU programming, it is also highly unlikely that the fan cannot or does not, go above level 3.

 

I totally agree that they are two different things, but the tipping point is the fact that there many reported observations of the cooling fan roaring away in the back.

Your report is the first time I have ever heard that the fan cannot be set by the control system at a speed greater than 3.