Thought 1 - I suspect that the charge/discharge cycle you describe is designed to warm the battery to some predetermined temp. However, I have never looked that closely at SoC during warmup to see if the 08 does the same thing. My opportunities are few, since wife drives the car daily

Thought 2 - I'm guessing that even though your highway speed prevents EV only mode, the requirement to warm the battery does cost some fuel mileage. I'm guessing that if you pre-warmed your battery with your EBH, and was able to run the same exact route with exactly the same enviornmental conditions, you would see better MPG with the pre-warmed battery. This is only a guess, but energy put into the battery MUST come from the ICE. If the battery was already warmed, the initial charge would ramp up to 53% with ICE on, and thereafter would only require the equivalent of a 'trickle charge' to keep it there. I believe that the reduced demand on the ICE to warm the battery would improve FE slightly.

Interesting how your 05 model acts. I do hope to check tomorrow morning when my wife and I both drive to the sport, boat, and vacation show, where we will contract "Spring Fever"

 

That sounds very logical.
Now here comes the illogical part.

During this charge-discharge, repeat cycles to warm the battery, I get:

27 IMPG for 30 seconds during the 12A charge phase, then
40 IMPG for 15 seconds during the 24A discharge "boost" phase.

Cruising with constant 53% battery I get ~29 MPG.
( sub-freezing conditions with ethanol )

I'm no math professor, but I was thinking the former looks like a better average to me. Kind of like the car is doing a built-in "Pulse & Glide".
-John

 

Doing some rough estimates, it's really too close to call with the equipment we have.
Assume I did that for one hour.

So thats 20 minutes of 40 MPG and 40 minutes of 27 MPG.
One hour will use 1.98 gallons.

Now assume 60 minutes of 29 MPG.
One hour will use 2.06 gallons.

But again, these are estimates.
I could actually get 29.5 MPG for one hour, then it tips the other way.
Or if the "boost" lasts for 18 seconds(per minute vs 20 ), it could tip the other way.

EITHER way... it looks very, very close. Not enough to fret over... But since some ENERGY is purposely being lost to HEAT... I would have to agree that the charge-discharge-repeat method should be worst.
-John

 

Today I ran the EBH all day and watched the power flow more closely.
I'm pretty sure I've got it nailed down.

The HV battery warmer kicks OFF at Tav 60.8'F (16'C).
It kicked off at exactly this point 3 times in a row.
Unplugging and plugging back in, it would draw 75w for a few seconds to a minute, then it would go off. I don't know how cold it needs to get to click back on.

The EBH takes full wattage (~410w) up to 100 degrees.
It's hard to get the block hotter than this... but... today after many hours, I got it up to 110'F in a garage. Then, I ran the car, and got the engine to normal temperature (~188'F).
The EBH may just get more resistance as it gets hot and the power tapers off. On a hot 188'F engine, the EBH fluctuates between 280w and 300w. It appears there is no theromostat to the block heater, which by its simple design is what I thought to be true all along.
-John

 

Thanks for all the updates John, especially the monitor on Tav battery shutoff point. I read all your updated posts in this thread. Agree, that the warmup cycling of SoC has minimal impact on overall FE.

Driving today I monitored the SoC closely as the HV battery warmed up from a starting point of 44.6F, reaching 66.8F in roughly a 13 mile trip. I honestly couldn't detect the fluctuations in the SoC up and down like you saw. However, my driving was not on an interstate at constant speed, so not really comparing apples to apples. This drive included some Regen as well as EV operation, all contributing to battery warming. OAT was ~35F this A.M. Bottom line, I can't say for sure if the 08 FEH uses the same software algorithm for battery warming as the 05?? It might if my driving style today replicated yours?

The 27 IMPG for the 12A charge phase, and the 40 IMPG for the 24A discharge/assist phase sounds entirely reasonable, and does appear like a software induced pulse & glide, exercising the battery, and providing warmth. The reason I think this is intentional batt warming strategy is because if you take off cold, immediately drive to the interstate and start cruising w/o using brakes and no EV mode, wouldn't it take forever to warm the battery? And I think that's why I didn't see anything like this today, because I was warming the battery due to my different driving scenario.

 

I'm assuming your saying on the interstate, it is ICE that is providing the power so the hybrid battery would have demand placed upon it and thus remain cold--cool? However, we have cabin heat and;

-The hybrid battery does operate on the interstate highway. It provide "assist" for demand as in acceleration--is it 10 hp for 40 seconds or 40 hp for 10 seconds?
- The hybrid battery also provides assist when it's state of charge exceeds 53%. I have noticed a lot of single digit amp assist during higher (40mph+) speed driving when the soc exceeds 53%

I have not noticed the hybrid battery "warm-up" proceedure as described by GPS1man but it makes sense.

 

See, now that's HUGE. 22 degrees in 13 miles. All your changes in speed equate to more demands on the battery.

I suspect it would be very close... considering Ford took out the plug-in heater!

Exactly! I think you nailed it.
-John

 

[quote=Billyk;159849]After extensive observations, my REGEN behaves normally, or nearly normal at very cold, even sub-zero temperatures. I do not think there is a program to cut-off regen simply because it is cold.

I think the car is smart enough to actually detect the slightest amount of wheel slip... THEN eliminate regen.

I've been driving sub-zero for a month, and roads have been clear and dry. I have had regen at every brake pedal press.

Today it was 31-32 degrees with heavy snow. My HV battery was 60 degrees from the plug-in heater, and I had no regen during braking. The car still went EV quickly, and I took off to 25-30 miles per hour in EV, but there was no regen at several stops. This car is so smart, it is a little scary. Either it detected the slightest amount of wheel slip ( I am a slow driver, and I personally didn't detect any slip or skid at all... ) or it has a wireless link to the National Weather Service.

Perhaps there is an event counter / event timer.
Perhaps after a wheel slip event... it says... okay, for the next XXX seconds there will be no regen until I see things improve.
Perhaps AFTER xxx seconds of no wheel slip, regen is turned back on?
Perhaps this A.M. I had a little wheel slip every couple minutes, so the timer never got zeroed out, and regen never came back on?

Perhaps in my several weeks of sub-zero I didn't have ANY wheel slip detected, so the car infered it was OK to use regen?

Sounds very likely to be the case from what I have observed.
-John

 

Yesterday (Sunday) ambient was abt 50F, Tav got up to abt 78F, and the HV battery sure could accept a large charge, and deliver a lot of current for EV and/or assist. Because we got the 08 FEH in late Oct 07, I haven't had much of an opportunity to experience the good summer time effects on hybrid operation that I've read so much about. The few warmer days we had last fall, I didn’t understand the FEH hybrid operation enough to appreciate the warmer weather then, plus the car was brand new and good FE was not yet obtainable. And then the cold weather set in. I really can't wait for summer now.

I hear the cooling fan come on periodically, but don't know what batt temp triggers the cooling fan? I've read the posts describing the temps that trigger the air conditioner coming on, but don't remember reading abt the cooling fan only?

BillyK - Agree abt the HV battery providing 'Assist' out on the highway when SoC exceeds 53%. It’s just that a cold battery is slow to warm without Regen or EV mode, so it doesn’t contribute much until it’s capable of receiving (Mxc), and then delivering (Mxd) an appreciable amount of current. A cold HV battery pack in the FEH/MMH is practically dead weight until it warms. Pre-warming it makes it much more useful from the beginning.

I just think there are many benefits from starting out on a cold morning with a warm battery. John’s description of his FEH SoC varying up and down is very interesting, and does appear to be an intentional means to more quickly warm the battery.

Neither my wife or I have much experience with the FEH on a highway trip, so I’m very inexperienced with it’s behavior at sustained highway speeds for extended periods of time. FYI, highway speed to me means 55-60 mph, so even if the speed limit is 70, I never do over 60.

 

I must raise my hand and say to the world that "I am not smarter than a 5th grader, neither am I smarter than my car".

I have driven from a warm building where the car was housed for a long time, and the battery was resonably warm. Then within 30 seconds being outside, the OAT dropped to well below freezing, but with the battery still warm, I had great Regen. So I also agree that OAT alone does not prevent Regen.

I feel compelled to report that I still haven't seen any slick streets or snow here in Louisville this winter, so I'm sure that ABS and AWD have never been utilized. I'd love to see snow once this winter to see how it behaves, then it can all melt the next day But it's not all bad just reading about your "wheel slippage" experiences from all you cold weather folks!!! Now Please don't throw any snowballs my way....