Here... this explains a lot. Becha want a battery heater now! -John


Put into perspective, you get 33 Horsepower of battery assist at 90'F.
You will only get 20 Horsepower of battery boost at 40'F.

 

Great Graph. Also explains when the FEH is in EV mode with a still cold battery, even the lightest touch on the accelerator can kick it out of EV compared to when the battery pack is warmed up.

 

So, is the graph a function of cold vs warm/hot battery capacity/capability or is it the result of firmware written to be conservative of SOC when the OAT hovers near freezing since regenerative braking cannot be as productive in that range?

Plus, at 40F the ICE will need to run fairly often for catalyst heating if not cabin and so there is not much to be gained, FE wise, in using the battery more heavily.

 

I guess I don't understand why regenerative braking can't be as productive when its cold. If the battery isn't the problem... why can't the generator produce just as much current when its cold? If its an ice handling problem I still don't understand until the ABS comes on (and regen is disabled) whats the difference if the force slowing the wheels is coming through the drive shaft or the brake pads... What am I missing?

 

Great questions, and I'm sorry I wasn't more clear originally.

The graph is a graph of the SOFTWARE/FIRMWARE setpoints... and not actual amps read with an ammeter.
MxD and MxC are maximum limits allowed... presumambly set to not over stress the battery, and extend longevity of life.

Again I stress this appears to be unrelated to outside air temperature.
It seems only to be based on battery temperature.

Regenerative braking works great for me at 10 below zero... if I keep my battery warm with a plug-in heater.

Catalyst temperature is usually not an issue. Even at 10 below, a few minutes of engine time gets it hot to 1400-1500 degrees, and 750 degrees is all that is required to clean the air.

CHT is the issue, and use of cabin heat circulates coolant water, and chills the Cylinder Head rapidly... when it is 10 below.

Warm battery, and no use of cabin heat ( req. gloves and hat! ) gives me all the EV I can use at 10 below zero. Fire up that cabin heat... and I get about 30 seconds per EV.

-John

 

John, does anyone know when the Ford patented technique began to be used on the FEH/MMH? Or if it has been adopted at all?

 

Remember, 99% of all patents are not realized in the real world.

A patent is protection of "intellectual property".
It does not have to ever be an object, machine, software, or device.
It is a protected idea.

I've been telling GaryG for years, the patents are interesting to read, and you can learn from them, but they tell you little about how this car was actually built.

I think Ford did not use the idea you refer to.

-John

 

Here is a "revised" graph with more data from today.
This was collected from 6 trips, over 4 separate days.
In the interest of science, I did not use the plug-in heater today.
Today ( 01-30-2008) it was -6'F to 4'F.
When I parked at work at 8am, it was -6'F and Tav was 41.0.
At noon, I checked on the car without starting, and Tav was 35.6.
I thought this was cooling very slow, so I opened the windows and liftgate and removed the HV battery carpet, so the metal battery lid had direct contact with less than 4'F air. But, by 5pm, the Tav had cooled to only 28.4'F. This illustrates to me, there is a lot of "insulation". Also another reason why the battery heats up on its own, and needs A/C in summer.
There is not much "radiant" transfer.
On the hot side, MxD - MxC = 19.0 amps.
On the cool side, MxD - MxC = 13.0 amps.
The lines are coming together, on the cold side.

-John

 

Well it did it again. Without using the plug today, the battery warmed itself.

I left work with outdoor air temp at 3'F and the HV battery was ~28'F.

The battery did charge-discharge-charge-discharge-charge-discharge.
From 28'F to 32'F the pack SOC went 49%-50%-49%-50%-49%-50%.

In 5 minutes, the HV battery was 32'F. I was using cabin heat too.

After 32'F, the SOC started to climb, 0.1% each cycle.
Never going lower than 49%.
49-50.1-49-50.2-49-50.3-49-50.4-49-50.5-49-50.6-49-50.7 etc.
I only had to go 9 miles, but I was facinated by this, so I set Cruise Control to 60 miles per hour and just kept driving to see what would happen.

It was always 12 amps in ( generator ) 24 amps out ( traction motor ).
27 MPG when charging, 40 MPG when discharging. 60 miles per hour.

After 31 minutes and 31 miles.... 49-52.4-49-52.5 then SOC went to 53% and it stayed at 53% like normal. Looking at the SG, Tav was 48.2'F.
The battery stayed at 48.2'F and 53% the rest of the drive home.

It has done this 3 times... all 3 times I started with a cold battery this month, but this is the first time I have watched it for this length of time.
Either this is specifically designed to warm the battery, or I've been lucky enough to have 3 battery recals in 1 month!

Thoughts?
-John

 

Today I left my car at work with no plug-in heat.
But I didn't try to cool it faster by leaving the tailgate open.

After work it was 8'F and the battery was 37'F.

The battery did the same thing, but started 1% SOC lower.

48%-49%-48%-49.1%-48%-49.2%-48%-49.3%....

When Tav hit 48 degrees, SOC went to 53% and the cycle stopped.
It went from 37 degrees to 48 degrees in about 15 minutes.
I was using cabin heat also if you think that had an effect.
-John