Okay, I think this is brand new info, because I have never read it before... so I will take credit for this discovery, unless it has been discussed before.

The HV battery pack has two cooling fans. (left half and right half of battery)
These are variable speed fans.

The fan speed varries with vehicle speed.
Even with a hot battery pack,
the fans only run 100% if the ICE is running.
As soon as you go into EV the fans drop to about 80% speed.
From 39 MPH to about 25 MPH the fans will run about 80% speed.
As vehicle speed slows 24 MPH to zero, fan speed gradually slows also.
At a stop, the fans spin very slow, maybe 10% speed... even if the battery is hot.

Now this seems totally ridiculous at first, but here's why I think they do that.
Noise.
The fans really are pretty darn loud at 100% speed, but I bet most of you never noticed. They only run at the noisiest level when the ICE is running, and the engine noise masks the fan noise. You are near the front ( by the engine ) and this over-powers the sounds of the fans in the back.

As soon as you go to EV, (39-25 MPH ) the fans drop to 80%. They are still mostly drowned out by road noise and/or wind noise. So you don't consiously notice the fans.

Slowing down below 25 MPH, road noise and/or wind noise decreases dramatically, and so does the fan speed. Even if the battery is still hot!

I think you have all noticed how QUIET this car is when you stop in EV.
If the fans were running at 100% at those otherwise silent stops, you all would trade your hybrids in before the first week was up.
They are that annoying.

As soon as you start moving again, the fan speed increases again.

This is of particular interest for hard-core hyper-milers, who demand more than typical from the HV battery. Extensive driving at slow speeds contributes to the battery staying hotter longer. For most drivers, this is a non issue, which I believe is why Ford chose the "quiet for customer" route vs. best for battery route.

Of course this applies only to the "middle ground" where the battery is warmer than optimum, and needs ventillation, but not hot enough to force the A/C on. If the A/C is forced on, then the engine is forced on, and noise from the fans is not an issue.

That being said, I have also found that designers noticed 100% fan speed can still be heard by the driver when the vehicle is stopped with ICE on. If the battery is hot and ICE is on, the fan speed will go from 100% to about 80% when you come to a full stop.

From an engineering standpoint, most stops are from 2 to 120 seconds long... and not having the fans blowing full speed for a short time will not hurt the battery.
However, with frequent and repeated stops, it adds up, and could eventually lead to a temperature warm enough to force the A/C on, not hurting the battery, but reducing fuel economy then.

I guess that was kind of a long post.
I hope everyone finds it interesting that Ford designers put so much thought into this. I hope hypermilers can use this new info to modify habits in warm weather and demanding battery useage.

-John

Excellent information. We need to get it added to the FAQ.

Is this "new info on the HV battery pack", or "info on a new HV battery pack"?

Best single LD trip: 35.3mpg

I too thought this was going to be about the new HV batteries when I clicked on it, so I made a slight change.

Good info John, good to know. Not that I'm doubting you at all, but where did you get the info? TSB? Engineer? Other?

First 4WD Hypermiler

Have you read the FEH FAQ?

Live in Michigan? Let it be known in Michigan Roll Call

Read My Automotive Blog at Rich Rambles

Hi Rich

What GPSman1 has posted about the 2 fans contradicts what the Diagnosis And Testing HVTB is noisy Section 414-03-13 &14. Here’s what written in the manual:

Normal Operation

NOTE: The fans may continue running for approximately 15 seconds after the ignition switch is turned to the OFF position. Once the fans turn off, they do not start again until the ignition switch is cycled to the on position.

With the ignition switch in the ON position and the engine running, the HVTB as 2 internal cooling fans that circulate climate-controlled air through the HVTB.

B1 Check The Internal Fans

NOTE: The cooling fans may run at various speeds due to varying vehicle and HVTB conditions related to ambient temperatures, length of fan run time and HVTB temperature. The fan speed increases with increased temperature and may run at 40% to 100% duty cycle. A fan running at 40% duty cycle will be much quieter than the same fan running at 100% duty cycle. During the on demand self-test, the fans will run at 100% cycle.

With the ignition switch in the ON position and the engine ON or OFF, use a stethoscope or equivalent listening device to probe the HVTB area for unusual or excessive noise. Compare the noise to a similar vehicle.

Is the noise coming from the HVTB internal cooling fan?

YES - INSTALL a new HVTB

NO - REFER to section 100-04

GPSman1 (John) should provide us with the source of this conflicting information he posted that you ask for.

Thanks

GaryG

"Duty Cycle" does not = speed.

Duty cycle of "40%" actually means something is on 40% of the time.

The 10% I refer to = 10% of the velocity of air, and to the best of my ability, also 10% of the noise. If the fan is running exactly 10% rpm is difficult to measure. My direct observations are the fan is hardly moving any air when the vehicle is not moving and ICE is off. Not even close to 40%.

This was observed in a 2005 FWD, built 12/2004.
The battery temp. on the message center was 32'C or 90'F at the time.
The air door closed when the battery hit 28'C. (82'F)

You all can verify by removing the HV battery air filter access panel, and filter, and operating the car & battery in warm conditions. What prompted me to study this was I never heard the fans when stopped in EV mode. No matter how warm the battery was. Once I was moving, the fan noise became obvious. The process I descibed is hard fact. Proven. One could apply a volt meter, if desired, and maybe 40% of the normal voltage = 10% blower / air speed. I have not applied such meter.

Cheers,
-John

P.S. Also, with electronic devices, sometimes the "power" is reduced by "pulsing" the power, not changing the voltage directly. Thus, a constant 12v supply "pulsed" to be on for 4ms and off for 6ms would be called a "40% duty cycle". This does not always mean the motor (in this case) is spinning 40% speed due to friction and load for example. At my workplace we have a 50 horsepower AC cooling tower fan, with blades larger than helicopter blades. It has a "VFD" or "variable frequency drive". 100% speed is when I dial in 60 Hz. 50% speed is when I dial in 45Hz. At 30Hz, the fan blade is barely moving. I'm sure the FEH fans are not AC, but pulsing the 12v DC would have a similar effect. My info DOES NOT contradict Gary's below, since Gary does not know what he is talking about, and does not understand everything he reads.

Keep on typing John, The fact is you made all of this up, you said:

"Okay, I think this is brand new info, because I have never read it before... so I will take credit for this discovery, unless it has been discussed before."

John, all I posted was what the manual says. You can take all the credit for your statements. To me, it is BS! You can't delete my post on GH as you do on Yahoo. Again, lets see a picture of your MTE for the many times I've ask you in the past.

Tell us how you were driving and knew about the 80% crap from 39mph speed to 24mph speed?

This Thread should ban you from posting here John!

GaryG

Gary, get off your fat butt, go outside and try it for yourself, then post.
It will embarrass you less.

I invite others to try this, with a partner either driving or sitting in the back seat with cover and filter removed. You do not need any special equipment. You just need to get the HV battery in the 30'C range, listen, and stick your hand in there and feel. ( there are no harmful moving parts within reach )

You don't need to take sides, just go out and see for yourself.
I don't post stuff until I go out and see it with my own two eyes.
So I ask you only post to this thread your actual experience.
At this point, opinions or theories won't help this thread.
Gary's just mad I discovered this first.
And to think... I actually posted this find since I thought Gary would find it very helpful to his MPG. I figured it wouldn't affect the average driver who didn't push the limits....
Thank You in advance.
-John

Colorado has cold winters. No good tanks last few months.
Been having 65 to 80 degrees days now.
While I wasn't quite ready for a new tank fill-up, I did this just for you.
( no one else cares )
I only have a crappy camera phone, then I gotta text mail it to myself.
Cost me $0.75 for 3 photos on my phone bill. Hope you enjoy it.







The Navi, as always, was about 2 MPG higher than this.
But I know you trust the ScanGuage more.
( For new comers, the orange pics are from an add-on device called a ScanGuage that shows what my previous tank was. The green pic is the FEH dash AFTER a new fill-up. Sorry, this is off topic. Thank GaryG. )

Regardless, they must be mighty quiet fans if one needs a stethoscope to hear them.

Ah, hybrids must always be serviced in pairs.



BTW, I am making fun of Ford, not Gary.

Best single LD trip: 35.3mpg