Had this happen a month ago, thought it was a fluke or something, so just blew it off as one of those things. So it happened again tonight, so I figured twice, maybe something to ask a question about.

So on my way home from work, same route for a few months now, 2am 40degrees. Watching the SG I have now, not then. I have Water temp as a gauge currently. Knowing I need to hit 140-150 to make EV possible. I go about 3/4 mile only up to 120ish (quick compared to my other cars!) all ready, at this point I'm getting on a highway; so no EV for a while. So cruise along for 3 miles at 60. Get up to 160+ on temp. Get to my usual exit, it's a tight turn, posted as 25mph, so like usual (I take it 30-35) I'm in L, and coast into the slowdown lane and start making the turn. As usual once it droped below 40mph it went EV. But only for a second, the RPM gauge quickly jumped back on, and stayed on for the rest of the turn and even the stop at the bottom. Temp still 160+, batt obviously should be full, outside temp still 40. Heat is on, but nothing forcing ICE on. Go my next 1/2 mile to my first stop sign, and it went EV like normal below 40, and so did the next 3 stops on the way home. If I recall correctly this same thing happened at the same place last time, on the off ramp.

So anyreason to enter EV just to pop out a slpit second later? Last time I think I just passed 5k, now I'm just past 6k miles. It's just wierd.

 

There are a number of sensor the vehicle relies upon to go into EV. What might have happen was too much torque required to remain in EV. GPSMAN1 recently stated too high of amps required byEV can cause ICE to come on.

 

Bryan. My 2005 does that all the time, and it drives me NUTS!!!!

So your car is "normal"... but it is still weird, I agree.

One possibility is: The battery was too full, and you were trying to put some regen into it, and it balked.

Another reason may be related to fuel and emissions.
There may have been unburnt fuel detected still in the system somewhere, and the car wanted to do a "purge".

I'm not sure of the "why" but I'm sure this happens to the majority of drivers.

-John

 

Mine does this all the time but only when in L and SOC is above 55.5%. I think the fuel is off when it is doing this, its engine braking because the battery is getting to full.

 

In the cold, with a battery that's not warmed up, it can't accept the same amount of charge as it can during the summer, which you'll notice if you have the energy display that until the vehicle is thoroughly warmed up, any more than a thin/moderate recharge arrow will cause the ICE to pop on, as the HVB simply can't accept that much charge in the cold state it's in, so it shunts the excess recharge power to the ICE. ICE temperature has nothing to do with this, it's a battery temperature and charge acceptance issue.

If that's the problem, you'll find that L has essentially become useless in the winter months, as all it does is pop the ICE on constantly. Go back to using D and the double tap, which will still cause the ICE to pop on occasionally, but won't do it as often. You can still use L to lower your speed at above 40 miles per hour, but until the battery is warmed enough to accept charge and give it, you'll find your EV recharge and discharge rates to be severely retarded. However, on longer trips, you can start using L again at times, but the FEH won't behave like it does in summer months. You may also start to notice that long periods of regen breaking also pop the ICE on, for the same reason, the battery can't take too much power until it's "thawed" a bit and gets all nice and warm, so it'll take regen for a while, then refuse it.

Unfortunately, the FEH has a bit of a split personality, behaving quite different in the winter months then in the summer months for those of us who have widely varying seasonal temperatures. I've already started changing my driving techniques, backing away from L and started using more of the winter driving techniques, though it's just hitting sub-freezing temps here in MI.

 

In the Prius world, there is a famous "The Five Stages of Prius Hybrid Operation".
http://techno-fandom.org/~hobbit/cars/five-stages.txt
The Stage 3a has a strange behavior of ICE idling until full stop for 5 or 10 seconds.

If the FEH control software is designed as same as Prius, it's the story.

Ken@Japan

 

Amazing... I was just logging on to start the exact same thread! Yesterday, for the first time, I have experienced the same strangeness in my FEH. It was 45 degrees outside and I would experience the ICE pop off and then suddenly pop on when I expected EV. I also noted that the regen needle wouldn't go as far right as expected. After the car really warmed up (maybe 20 minutes) the strangeness would disappear... I was using L to brake too...

So what are the winter driving techniques? I am currently getting 34.8 mpgs and other than the first tank this is the worst I have done...

 

Mine behaved similarly in recent cold weather. I drove for less than ten minutes in very light traffic, then five minutes or so at 60 MPH. On exiting, ICE shut down in 'L' below 42, then came back on a second later. It revved to +/-1500 RPM for a moment. I surmised that the ICE got warm relatively quickly while the battery pack, hanging out back, was still cold. I don't know much about batteries but figured that maybe a cold battery can not accept as much charge, so the ICE was spinning some of it off.

I also noticed that my regen hardly works in cold weather using the brake pedal. The gauge stays right in the middle until I've diven for a while and both the interior and the ICE are plenty warm. It will still regen if I use 'L', but not with the pedal until everything's been running for a while.

 

Cris-
34.8 and you're upset? I'd kill for that right now. I was holding steady at 30 MPG for a while but have dropped to 28. The car is garaged overnight and we haven't been below 20 too often.
I have the same issues as all the others--no regen, no electric assist when pulling a hill (I hit 5000 RPM and just got to 40 MPH on my on-ramp--normally I use about 3000 and get close to freeway speeds when the electric motor kicks in), rarely goes into EV (I went all last week without it kicking in at all, and no changes in routes or anything like that). After 20 minutes or so the EV can kick in.
Also, and this may be unrelated, my odometer came on when I was getting into the car the other day. The problem? The keys were still in my purse. I'd had some earlier electric issues with gauges going crazy after I'd removed the key but the dealer couldn't find anything. Maybe I'll take it to another one and see what they can do.

 

The EV quirk I've experienced is the ICE seems to engage easily below 40mph during the very first EV after a cold start. This happens even when the Scangauge shows water temperature well above 120F.

Coming off a freeway exit when the engine is very warm I can stay in EV down to 120F or 40% SOC even with decent stop sign/traffic signal accelerations.