When the traction battery is relatively cold or hot, it will not accept full regen. current, and is prone to shut down suddenly. I had this happen once on a cold morning in which there was a "clunk" sound and followed by diminished braking needing more pedal. I noticed that the regen needle had swung up to neutral, in spite of the SOC only about 2/3rds.

I suspect this sound was made by a major-league circuit breaker opening to protect the battery. I try to limit the intensity of regen braking as suggested by Don R. because of this, particularly when first driven.

Pete

 

OK. I think the times I've seen it were shortly after startup. I don't recall any 'clunks' but...this is the Lexus version. The outside temps weren't extreme...but it was within a mile or so of leaving our driveway.

Benton 22may08

BTW, our overall mileage is in the sig, but I've been driving it this week while the wife's out of town and have pushed the average for this tank up to 29.5 mpg on ~ 75% city. She says she's willing to listen, if I can give her a couple tips for boosting the mileage.

 

The clunk thing only happened once, on a quite cold morning with heavier than usual braking. As the Lexus is the same under the skin, this was loud enough to have gotten through a little more insulation, and felt as much as heard! Surprised me enough to pull over and shut down, but the usual is just regen stopping rather suddenly on a long downhill to a stop when cold.

Is your wife having too much fun dragging the good old boys at the lights, or just charging up to them like mine does? You've got to work hard to get city milage that low unless the trips are short.

Pete

 

Only if she drives way different when I'm not with her. So far as I know, she's actually a more 'gentle' driver than me. I think the things that cause the overall mileage (90-95% her since it's her daily driver) to be so low are:
o break-in. It has just 5k on it now
o cold weather driving, it's been in service since last Sept. It sleeps in an unheated garage tho' the Portland area is pretty mild in the winter
o she has a short commute -- about 5 miles each way, maybe. Mine is more like 10 miles each way.

But on top of all that, I imagine she's just been driving it exactly like her previous car, whereas one of the things I've found is that to boost the mileage I have to actively work on coasting.

Also, I think we really hadn't come to grips with the penalty for the warm-up time, so she's probably not working the errand combining thing as hard as she could (and so paying yet more warm-ups.) I'm going to look into the block heater idea.

Benton 23may08

 

A 5 mile commute starting with a cold engine will really kill MPG. My commute is just 9 miles and my overall mileage is impacted because of this.

Hybrid technology rewards long commutes, living in moderate climates (not to hot or cold), and driving routes in suburban or rural environments where speed can be kept between 30 to 45 miles per hour.

I have also found that very gentle and short rolling landscape (not significant and long grade changes) helps increase mileage when driving below 45 mpg. The engine runs on the gentle upgrade and shuts off and coasts and possibly runs on electric on the down grade. The engine must run on occasion any way and it operates more efficiently under the added load that the upgrade provides. The up-grades must be short enough to prevent the battery from reaching full charge when cresting.

My average over about 600 gallons of fuel is about 27 MPG. Cold Chicago winter weather also is a major mileage hit. My tank averages can be 22- 25 mpg in winter and 28-31 in summer for the same commute.

 

But who knows what may possess her when alone, with the power of a raging beast at her command?

Probably, though, the short trips and coolish weather - I imagine a lot like it is here in Monterey - land of the eternal 50's and 60's. In NW Florida, I got a consistent 28 or so in the city, but here, with shorter trips, cooler, and many hills, 23-24 is more like it, a bit less in winter. My garage stays in the low to mid 60's, but I have considered a block heater, as it's barely warm on some short trips.

Pete

 

An EBH set on a 2 - 3 hr cycle will make a 6-8 mpg difference for commutes of under 10 mi. In addition to shorter times to reach S3/4, more battery capacity becomes available for regen braking.

As fuel prices increase above $4/gal, the EBH economics become more and more favorable.

 

Um, I'm new, but am an eng'r. EBH is Electric Block Heater. What is S3/4? Also, I'm driving a Lexus RX. I'm assuming the unit that fits the Tojo Highlander Hybrid would also work on my RX? I'm about to drop an email to the folks I dealt with at that dealership to see what they have to say...

I was about to take a photo, I was so proud, of the mpg display, since I've been driving the wife's car for the week and had run it up to 30.2 mpg over 200 miles vs. her number in the sig. Then I thought, "Gee, the screen is dusty, I should wipe it off." and hit the reset button while dusting. Then drove my normal commute, surface streets on a warmed up car, and got about 35 mpg for my normal work commute, 18 mile round-trip. Somehow, that's just astonishing in a car that'll still bark the tires if you nail it.

Benton 24may08

 

Check out the "Articles" by putting your cursor in the blue Wiki box above and clicking on "Articles", which includes an excellent one by Evan Fusco on self-installation of an EBH on an '06 HiHy, with both graphic and very clear photo illustrations. He ordered it from a Canadian dealership and gives the link - he couldn't get it in the States. Should work with the 400h also, as it is mechanically identical to the i4WD HiHy.

I'm thinking a little thermostatically controlled ceramic heater blowing into the battery vents to get battery temp into the 70's would be worthwhile also, as this range seems to be the optimum for accepting regen current.

Pete

 

I have been using the Toyota engine block heater for over a year and a half now. I use it every day - summer and winter - though in winter I keep it on for three hours while in summer about 1.5 hours.

It definitely does help to get the vehicle into the more efficient hybrid operating modes faster. Even with the EBH though, when the temperature is below 20 to 30 degrees F, my mileage suffers significantly and I get 23-25 mpg.

The engine water temperature is about 95-105 F when starting out in the morning in such cold weather with the EBH set for 3 hours. The Hybrid battery is still cold and this also affects the warm up. I could put a heater in the passenger compartment though I don't know when diminishing returns kicks in.

I created a special plug mount below the bumper and a special spring relieved power cord attachment for the EBH so that if I forget to unplug the EBH in the morning, it will harmlessly unplug itself when I back out of the garage. You don't want frayed cords and sparks where grease and oil may reside.