06 Highlander Hybrid: Does yours do this?

The vehicle is not designed to needlessly start the gas engine, but it is designed to start the gas engine if the battery's state of charge falls below the optimal range or if load on the drivetrain exceeds a certain amount. The vehicle's propulsion is supplied by a combination of the electric and internal combustion motors. If the rate of acceleration is more than the electric motors can provide, the internal combustion motor will kick in.

Some accessories draw more power and deplete the battery more quickly, like the air conditioner (including the front defogger), rear defogger, headlamps, wipers, blowers.

The dealer can plug in a diagnostic scanner to check the hybrid system's operation, but it sounds like yours is functioning properly.

I remember a report on the Prius that said coasting to a stop does not recover much energy. It went on to say that the most efficient recovery of energy happens when the motor is generating about 60 amperes, which corresponds to pretty heavy braking. Of course, with passengers in the car, heavy braking won't be treated with kindness, and waiting until the last 20 ft to put on the brakes might be courting disaster. But say you're on a freeway off ramp from driving 70 mph and there's nobody following you - - then you might hit the brakes and bring your speed down to 25 mph in a fairly short distance, like 100 ft or so. Then you might find the engine willing to let the electric motor run a while before starting up - - especially if you can put it in cruise control at 34 mph for a while. At least that's how my Prius behaves.

Chuck, do you ever put the transmission in B (brake) to recover energy? I am starting to experiment with it, but haven't drawn any conclusions yet. Here is a relatively good article on improving Prius mileage, most of which probably applies to the Highlander Hybrid.

And here is a not-so-good article on pulse and glide, the method by which some drivers got 100 mpg, probably at 35-40 mph on a closed track.

Seems like putting the transmission in N (neutral) is the same as gliding by feathering the accelerator, but some advice columns on the internet say to avoid using N.

AFAIK, it's actually "B(attery)", though a lot of people think as you do. I use it only occasionally; on the whole my Prius does a good job of maintaining its charge ("B" is for charging where you the driver know better what the landscape ahead will be like) and handling the braking. However, I try not to brake hard unless it is necessary: partly for the same reasons one tries not to in any vehicle; partly to encourage the car to bank the energy as charge in the battery, not waste it as heat in the brake pads.

Sorry, forgot to add this to my other post. IIRC, the manual too advises against use of N(eutral). In practice, it is not needed. As you say, careful pressure on the accelerator (and oddly on the brake, too) puts the car into neutral (depending on how anxiously the charging system is watching the battery condition -- when the charge needs topping, finding the pedal's neutral setting is much trickier).

I've spotted several factual errors in the manual, many probably the result of copy 'n' paste from manuals for non-hybrid Toyotas. I've also spotted at least 20 grammatical errors, but I read Usenet so I'm used to that type of thing. ;-}

Observation indicates that the best mileage is produced in one of two conditions: 1) in accelerator glide or Neutral; 2) when operating exclusively on electric motor at < 40 mph with battery fully charged (green not blue bars to the top).

In other words, I see no reason not to use Neutral. The only problem is that the '07 Prius transmission won't go from N into Battery/Brake without first going into Drive, so at the top of a steep hill, a quick double-shift is necessary if I want to save the brake pads.

Maybe the manual advises against use of B and N because drivers might leave the vehicle in the wrong mode: N when the light turns green, or B when trying to accelerate quickly.

Aha, that explains why accelerator-pedal glide is hard to achieve when the car is warming up. I have never gotten > 30 mpg during the first 5 minutes (I'll have to ask my wife if she has) so I bet a plug-in battery charger would start the car in battery-full mode and yield better mileage on short trips.

That manual is an annoying piece of work all over. As I laboured through it, I estimated at least a third could have been got rid of by removing repetition.

Keep in mind that mpg improves as the petrol engine warms. That will be why they go to the trouble of storing engine coolant in an insulated container between runs. And the engine starts at a low speed. Even a really "clever" battery charger seems unlikely to help there unless the trip is laughably short, such as a few hundred feet, and then you would have to keep the speed down.

As Ray O said, this is to charge the battery. But you have a point -- it would be nice to have a setting for "do not use gasoline engine until notified otherwise."

A friend got only 24 mph on a long trip from Texas to California. The Highlander Hybrid is more overrated than the Prius for EPA mileage! Consumer Reports got 16/28 in their testing, which, it should be noted, is better than the EPA number for highway mileage.

The Highlander is not very aerodynamic and weighs over 4400 pounds.

In an earlier post (months ago), I described experiments done on my UK-spec Prius T4, which comes with an "EV" (Electric Vehicle) button. With the current battery design, you don't get what any normal driver would regard as a useful open-road range; it's for pottering about in places where exhaust fumes would be disliked.

As is the case with all hybrids one is not likely to save, in fuel costs, anywhere near the premium it costs to buy the vehicle during the time the average new vehicle buy keeps their vehicle. Those that keep them longer than average needs to be concerned about the battery repayment cost. If your are rich and your intention is to save the world, that's another story. ;)

mike

Thanks a lot-- I found (what I think is) the thread from September. Interesting that when your battery gets 3/8-charged, the hybrid system started up the gasoline engine. I wonder if there's something magic about 3/8 charge? I always thought NiMH batteries could go near 0% without damage. Many Lithium-ion batteries are damaged reaching 0%.

The UK-spec Prius T4 "EV" mode would be useful in a parking garage.

I suspect if you had a plug-in battery charger to make the battery start out full, EV might be useful for more than 2 kilometers.

The hybrid controller on the Prius keeps the NiMH batteries at between 45% and 65% charged to maximize battery life. Here is an article about how it works:

Great theory, except for one teensy-weensy teeny tiny problem... Let the HV battery pack drain down to zero with the engine still off, and you are stuck. Even though it may not damage the battery pack.

You need the HV Battery to start the gasoline engine, it doesn't have a 12V starter motor. And you want to stop discharging it at 3/8 on the off chance that the computer is being a *bit* too optimistic about the battery charge level, leave a cushion.

My Norelco razor is starting to do that because the battery pack is getting old, it counts the charge down to around "10 minutes left", and then it suddenly stops dead. (The display has been recalibrating lower after each charging, but it hasn't caught up with reality yet.)

If that was the Prius starting battery you'd be walking.

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I now feel, from later experiments, that the car switched back to normal mode from EV because of the speed it had reached, rather than the charge level. However, the points made by Ray and Bruce would seem valid. Either way, attainable range on EV is not big.

-- Andrew Stephenson

Thanks, but that link has Camry information and nothing I can find about the Prius or hybrid synergy drive. Can you give another URL?

I found the link I posted by doing a google search. You could try searching "Prius hybrid synergy drive battery" and see what comes up. For what it's worth, the Prius and Camry hybrid drive essentially work the same way, and the state of battery charge will be the same.