Thanks for the info Gary. I'd be nice to have a way to do the double-tap without the brake lights going off as I prerry much always drive with some traffic, and would not want to cause all the cars behind me to slam on the brakes everytime I want to go EV.

Cheers
rcomeau

 

As previously noted, Ford has a patent that describes a (safety issue??) technique wherein the level of regenerative braking is substantially reduced if the prevailing temperature is hovering around or below freezing.

Now I don't know about the FEH/MMH, but the system in my Lexus shares one OAT sensor for the engine control, climate control, and OAT readout on the instrument panel.

Could your OAT sensor be open and the hybid system "thinks" it COLD outside?

 

It's good that your paying attention to the people behind you. My Driver's Ed teacher taught me that you need to check your rearview mirror enough to always know what's behind you. Because I always try to keep the HV battery on the drained side, when I need to maintain the flow of traffic with cars behind me, the battery is filling for a longer EV ride the next time I get the chance.

The other day I was driving my normal route 20 miles to WPB and my SG current trip read 61.4mpg when I parked. Had a nice tail wind, but did not key-off FAS any. The battery heat wouldn't allow EV mode in "L" much, but "N" brake tapping saved the day.

It's starting to cool down here a little and I think I'm going to break my own records this year. South Florida is the place for the FEH in the winter. Sorry for the snow and ice in the northeast and northwest now, but I had to put up with the heat this summer.

Has anyone tried the "N" brake tapping when "L" or "D" wouldn't work? How about in the real cold climate after engine warm-up?

GaryG

 

If the HV battery has been sitting in cold ( below freezing ) for a number of hours, I get very, very little regen, and the L gear trick is useless. The battery just can't take a charge.

But also, in very cold, it can't PRODUCE much charge either, so I think the computer deliberately holds back on going to EV as the battery would be needed to restart. However, using it is the best way to warm it. So it is a catch 22 condition. ( not sure where that phrase comes from? )

The ONLY way to get EV is to have engine coolent above 141'F and enough minutes gone by ( 5 min ) to heat the cat. converter... THEN shift to N and use the double tap of the brakes method. This works most of the time, but not all the time.

Also, I shift to N when in EV to keep EV when stopped at long lights, drive-up bank tellers, Burger King Drive-thru, etc. as in VERY cold conditions, you can only keep EV for about 30 seconds at a time.
Does this produce more "cold(er) start" emissions... maybe... but this should be offset by not burning any gas during those 4-5 minutes in the burger drive-thru.... saving money in the process...

Again, your water temp must be over 141'F to enter EV mode, and above 125'F to keep EV mode when there. At about 15'F outside temperature, the car looses about 1 degree of water temp. every 3 seconds when at a stoplight. I have my radiator front 100% covered with cardboard, and have a hard time keeping my radiator water above 141'F in stop and go city. At 50 MPH, it's only about 161'F and most cars have a thermostat set to 180'F!!!!!

Also, when driving at around zero or in minus degrees, the ICE RPM's never fall below 1350 rpm in my FEH. As you know, the car must be at 1000 RPM to shut down and go to EV. Thus, at zero and below, EV is impossible, no matter how warm the battery is.

-John

 

The US patent recently issued to Ford says that regenerative braking is substantially reduced when the outside temperature is near or below freezing. Expect the ICE to continue operating virtually full time in those climates.

Probably to reduce instances of loss of directional control due to regenerative, "engine", braking on a FWD vehicle operating on a low traction roadbed.

 

Naw.... you're heading down the wrong track... It's not that.
I'm below freezing half of the year, and on snow only a few days a year.
Traction is not at issue. If there is any wheel skid detected at ANY temperature, all REGEN is deactivated. They've already covered the bases on that.

In cold temperatures, the battery is the issue. It can't take the wattage regen creates when it is cold.

 

I live in MI... I've seen the temperature at 17F and my boost guage still moves to the charge when I let off the gas. Where is that charge going if not into regen? I also seem to see regen when I brake as well, maybe not as much but I'm pretty sure I saw it on the NAV... so I'm a bit confused.

It sounds like there is alot of belief that all the MPG loss is due to the battery. The loss just in the engine efficiency is pretty darn significant. At highway speed I'm seeing about 4-5MPG less than during the summer. The battery is not used much at highway speed as all the current for the motor is coming from the generator.

 

Okay... let me re-phrase....

In very cold weather, the battery cannot take all of the wattage that regenerative braking normally creates, so the braking/charging effect is greatly reduced. Down to about -40'F you will get a trickle.

Yes, cold for sure affects the ICE as well.

-John

 

There is no way to know, really, when or what hybrid model year in which the patent was implemented, if at all.

But now we're into the realm of reactive vs pre-emptive...

Oftentimes once wheelspin/slip is detected (and reacted too) it is already too late, especially so for FWD or front torque biased AWD vehicles. The fact that you have VSC doesn't mean you should EVER begin to rely on it.

 

With the cold weather snap we just had, my MPG has dropped dramatically. About 4 or 5 MPG!

In the sub-freezing weather, I just can't get the ICE to shut down for any reasonable length of time. I was stuck in traffic for about 15 or 20 minutes, and during that entire time, the ICE ran. At least for me, it seemed like idle alone wasn't enough to keep the system very warm. It wasn't until the traffic started to move again, and I was able to drive at around 25MPH for 10 minutes, that the car was finally warm enough to allow the ICE to shut down. And even then, with a fully charge battery, I could not drive for more than a few minutes on EV, when the ICE would just start up again.

This is going to be my first winter with a hybrid. If this is typical cold weather operation, I don't think I am going to save very much gas.